Progress in Energy and Combustion Science 36 (2010) 327–363Contents lists available at ScienceDirect Progress in Energy and Combustion Science journal homepage: www.elsevier.com/locate/pecs A review on the utilization of fly ash M. Ahmaruzzaman* Department of Chemistry, National Institute of Technology Silchar, Silchar-788010, Assam, India a r t i c l e i n f o a b s t r a c t Article history: Received 8 August 2009 Accepted 10 November 2009 Available online 28 December 2009 Fly ash, generated during the combustion of coal for energy production, is an industrial by-product which is recognized as an environmental pollutant. Because of the environmental problems presented by the fly ash, considerable research has been undertaken on the subject worldwide. In this paper, the utilization of fly ash in construction, as a low-cost adsorbent for the removal of organic compounds, flue gas and metals, light weight aggregate, mine back fill, road sub-base, and zeolite synthesis is discussed. A considerable amount of research has been conducted using fly ash for adsorption of NOx, SOx, organic compounds, and mercury in air, dyes and other organic compounds in waters. It is found that fly ash is a promising adsorbent for the removal of various pollutants. The adsorption capacity of fly ash may be increased after chemical and physical activation. It was also found that fly ash has good potential for use in the construction industry. The conversion of fly ash into zeolites has many applications such as ion exchange, molecular sieves, and adsorbents. Converting fly ash into zeolites not only alleviates the disposal problem but also converts a waste material into a marketable commodity. Investigations also revealed that the unburned carbon component in fly ash plays an important role in its adsorption capacity. Future research in these areas is also discussed. Ó 2009 Elsevier Ltd. All rights reserved. Keywords: Fly ash Adsorption Wastewater Heavy metals Dye Organics Zeolite Construction Contents 1. 2. 3. 4. 5. 6. 7. 8. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 328 Properties of coal fly ash . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 329 2.1. Physical properties . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 329 2.2. Chemical properties . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 330 Properties of biomass ash . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 330 Fly ash utilization . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .331 Adsorbents for cleaning of flue gas . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .331 5.1. Sulphur compounds . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 331 5.2. Adsorption of NOx . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 332 5.3. Removal of mercury . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 332 5.4. Adsorption of gaseous organics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 333 Removal of toxic metals from wastewater . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .333 6.1. Adsorption of various types of heavy metals on fly ash . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 334 6.2. Adsorption mechanism and kinetics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 335 6.3. Adsorption isotherms . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 336 6.4. Factors affecting adsorption of metal on fly ash . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 337 Removal of other inorganic components from wastewater . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .337 7.1. Removal of phosphate . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 337 7.2. Removal of fluoride . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 338 7.3. Removal of boron . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 338 Removal of organic compounds from wastewater . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 338 8.1. Removal of phenolic compounds . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 338 * Tel.: þ91 3842 233 797. E-mail address:
[email protected] 0360-1285/$ – see front matter Ó 2009 Elsevier Ltd. All rights reserved. doi:10.1016/j.pecs.2009.11.003 328 9. 10. 11. 12. 13. 14. 15. 16. 17. 18. 19. M. Ahmaruzzaman / Progress in Energy and Combustion Science 36 (2010) 327–363 8.2. Removal of pesticides . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 339 8.3. Removal of other organic compounds . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 340 Removal of dyes from wastewater . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 340 9.1. Azo dyes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 340 9.2. Thiazine dyes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 340 9.3. Xanthene dyes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 342 9.4. Arylmethane dyes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 342 9.5. Other dyes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 342 Leaching of fly ash in water system . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 343 Synthesis of zeolite . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 344 11.1. Application of zeolite synthesised from fly ash . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 346 Construction work/industry . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 348 Lightweight aggregate . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 353 Road sub-base . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 353 Mine backfill . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 354 Cost estimation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 354 Barriers to utilization . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 355 Future research and prospects . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 355 Conclusion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 356 Acknowledgement . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 356 References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 356 1. Introduction Since wide scale coal firing for power generation began in the 1920s, many millions of tons of ash and related by-products have been generated. The current annual production of coal ash worldwide is estimated around 600 million tones, with fly ash constituting about 500 million tones at 75–80% of the total ash produced [1]. Thus, the amount of coal waste (fly ash), released by factories and thermal power plants has been increasing throughout the world, and the disposal of the large amount of fly ash has become a serious environmental problem. The present day utilization of ash on worldwide basis varied widely from a minimum of 3% to a maximum of 57%, yet the world average only amounts to 16% of the total ash [1]. A substantial amount of ash is still disposed of in landfills and/or lagoons at a significant cost to the utilizing companies and thus to the consumers. Coal is a dominant commercial fuel in India, where 565 mines are operated by Coal India and other subsidiaries. In 2003, production of hard coal was 358.4 Mt.; while utilization was 407.33 Mt. India is the sixth largest electricity generating and consuming country in the world. Fly ash can be considered as the world’s fifth largest raw material resource [2]. An estimated 25% of fly ash in India is used for cement production, construction of roads and brick manufacture [3]. The fly ash utilization for these purposes is expected to increase to nearly 32 Mt by 2009–2010. Currently, the energy sector in India generates over 130 Mt of FA annually [4] and this amount will increase as annual coal consumption increases by 2.2%. The large-scale storage of wet fly ash in ponds takes up much valuable agricultural land approximately (113 million m2), and may result in severe environmental degradation in the near future, which would be disastrous for India. Fly ash particles are considered to be highly contaminating, due to their enrichment in potentially toxic trace elements which condense from the flue gas. Research on the potential applications of these wastes has environmental relevance, in addition to industrial interest. Most of the fly ash which is produced is disposed of as landfill, a practice which is under examination for environmental concerns. Disposal of fly ash will soon be too costly – if not forbidden. Considerable research is being conducted worldwide on the use of waste materials in order to avert an increasing toxic threat to the environment, or to streamline present waste disposal techniques by making them more affordable. It follows that an economically viable solution to this problem should include utilization of waste materials for new products rather than land disposal. Fly ash is generally grey in color, abrasive, mostly alkaline, and refractory in nature. Pozzolans, which are siliceous or siliceous and aluminous materials that together with water and calcium hydroxide form cementitious products at ambient temperatures, are also admixtures. Fly ash from pulverized coal combustion is categorized as such a pozzolan. Fly ash also contains different essential elements, including both macronutrients P, K, Ca, Mg and micronutrients Zn, Fe, Cu, Mn, B, and Mo for plant growth. The geotechnical properties of fly ash (e.g., specific gravity, permeability, internal angular friction, and consolidation characteristics) make it suitable for use in construction of roads and embankments, structural fill etc. The pozzolanic properties of the ash, including its lime binding capacity makes it useful for the manufacture of cement, building materials concrete and concrete-admixed products. The chemical composition of fly ash like high percentage of silica (60– 65%), alumina (25–30%), magnetite, Fe2O3 (6–15%) enables its use for the synthesis of zeolite, alum, and precipitated silica. The other important physicochemical characteristics of fly ash, such as bulk density, particle size, porosity, water holding capacity, and surface area makes it suitable for use as an adsorbent. From the perspective of power generation, fly ash is a waste material, while from a coal utilization perspective, fly ash is a resource yet to be fully utilized; producers of thermal electricity are thus looking for ways to exploit fly ash. The cement industry might use it as a raw material for the production of concrete. Coal fly ash discharged from power plants can also be utilized as a byproduct, and its use in recycling materials for agriculture and engineering is also being studied [5,6]. The conversion of fly ash into zeolite has also been widely examined [7]. Another interesting possibility might be use as a low-cost adsorbent for gas and water treatment. Several investigations are reported in the literature on the utilization of fly ash for adsorption of individual pollutants in an aqueous solution or flue gas. The results are encouraging for the removal of heavy metals and organics from industrial wastewater. This paper will review the various applications of fly ash, including low-cost adsorbents for flue gas cleaning, wastewater treatment for removal of toxic ions M. Ahmaruzzaman / Progress in Energy and Combustion Science 36 (2010) 327–363 Nomenclature A B Ce Cs Ct k1 k2 ks ki qe qt DG0 DH0 K Kd Kf m 1/n q R S DS0 t1/2 V Vb Vm x/m b Redlich–Peterson constant Redlich–Peterson constant equilibrium concentration of the solution surface concentration solution concentration pseudo-first order rate constant pseudo-second order rate constant mass transfer co-efficient rate parameter of intraparticle diffusion control stage amount of adsorbate adsorbed at equilibrium (mg/g) amount of adsorbate adsorbed at any time t (mg/g) standard Gibb’s free energy of adsorption (kJ/mol) standard enthalpy change of adsorption (kJ/mol) Langmuir equilibrium constant distribution co-efficient Freundlich constant mass of the adsorbent adsorption intensity heat of adsorption universal gas constant specific surface area standard entropy change of adsorption (JK1 mol1) half-life period eluted volume (ml) volume of effluent at break point (ml) Langmuir monolayer adsorption capacity amount adsorbed per unit of the adsorbent heterogeneity factor Abbreviations AASHTO American association of state highway and transport officials ABS acrylonitrile butadiene styrene ACC autoclaved cellular concrete ACCG activated carbon-commercial grade ACLG activated carbon laboratory grade Acid Orange 7 p-(2-hydroxy-1 naphthylazo)benzene sulfonic acid AEA air entraining admixture AMD acid mine drainage ASR alkali–silica reaction ASTM American society for testing of materials BDTDA benzyldimethyl tetradecylammonium BFA bagasse fly ash BG Brilliant green CANMET Canada centre for mineral and energy technology CC char-carbon CCP coal combustion products CCB coal combustion by-products CEC cation exchange capacity CFA coal fly ash CFS chemical fixation and solidification and organic matters, synthesis of zeolite, mine backfill, light weight aggregate, road sub-base and construction/cement applications. 2. Properties of coal fly ash Characterisation of fly ash in terms of composition, mineralogy, surface chemistry and reactivity is of fundamental importance in the development of various applications of fly ash. CPC CR DDD DDE DEF DNP DTA EDTA EPA FA FAZ-Y FGD FTIR GGBFS HDTMA HeCB HVFA HSFA IFA LCA LOI MB MSWI MV NMR NPC OG OPC PPC RB RBB RCC RHFA RPC RY SDS SSA SEM SMZ-Y TCB TCLP TEA TEM TOC TPABr USEPA UHPC TNT UHPC WC XRD XRF ZFA 329 cityl pyridinium chloride Congo red 2,2-bis (4chloro-phenyl)-1,1,-dichloro ethane 2,2-bis (4chloro-phenyl)-1,1,-dichloro ethane delayed ettringite formation di-ntrophenol differential thermal analysis ethylene diamine tetraacetic acid Environmental protection agency fly ash fly ash based zeolite flue gas desulphurization Fourier Transform infrared spectroscopy ground granulated blast furnace slag hexadecyl tetramethyl ammonium 2,21,3,31,4,5,6-heptachlorobiphenyl high-volume fly ash high-sulphate fly ash impregnated fly ash life cycle assessments loss on ignition methylene blue Municipal solid waste incinerator bottom ash methyl violet nuclear magnetic resonance normal Portland cement Orange-G ordinary Portland cement Pozzolana Portland cement rhodamine B Remazol brillant blue reinforced concrete construction rice husk fly ash reactive powder concrete rifacion yellow HED sodium dodecyl sulphate sewage sludge ash scanning electron microscope surface modified fly ash based zeolite 2,3,4-trichloro biphenyl Toxicity Characteristic Leaching Procedure tetramethyl ammonium transmission electron microscope total organic carbon tetraporpyl ammonium bromide United States environmental protection agency ultra high-performance concrete tri-nitro toluene ultra high-performance concrete wood charcoal X-ray diffraction X-ray fluorescence zeloite fly ash 2.1. Physical properties Fly ash consists of fine, powdery particles predominantly spherical in shape, either solid or hollow, and mostly glassy (amorphous) in nature. The carbonaceous material in the fly ash is composed of angular particles. The particle size distribution of most bituminous coal fly ash is generally similar to that of silt (less than a 0.075 mm or No. 200 sieve). Although sub-bituminous coal fly ash chemical composition. Since such fly ash eventually is incorporated in concrete. it is generally slightly coarser than bituminous coal fly ash. as a blended cement component shares some of the requirements for both raw material and direct concrete admixture use. Table 1 compares the normal range of the chemical constituents of bituminous coal fly ash with those of lignite coal fly ash and sub-bituminous coal fly ash. The colour of fly ash can vary from tan to gray to black. while those with a SiO2 þ Al2O3 þ Fe2O3 content between 50 and 70 wt% and high in lime are defined as class C. kaolinite. 3.330 M. Especially to be considered here are rheological effects. The color of the ash and its effect on the color of the final concrete to be produced by the blended cement may also be of importance. in combination with silica and alumina. Lignite and sub-bituminous coal fly ash is characterized by higher concentrations of calcium and magnesium oxide and reduced percentages of silica and iron oxide. although the post compaction cementation provided by some high-calcium fly ash is likely to prove beneficial. Class C fly ash may have reported calcium oxide contents as high as 30–40%. with varying amounts of carbon. The several distinct end uses of fly ash differ considerably among themselves in the stringency of the properties required in the fly ash for its successful utilization. and to some extent of the content of spherical particles. Some road base applications of fly ash depend on the physical effects of fly ash incorporation rather than its reaction with lime. alumina. Very little anthracite coal is burned in utility boilers. However. In addition to being handled in a dry. Component (wt. etc. the high-calcium Class C fly ash is normally produced from the burning of low-rank coals (lignites or sub-bituminous coals) and have cementitious properties (self-hardening when reacted with water). which may be limiting in most other end uses. fly ash is also sometimes classified according to the type of coal from which the ash was derived. i. strength development characteristics. whereas high-calcium fly ash consists of quartz. the fly ash used should be relatively insensitive to such variations. The dominant mineral phases are quartz.. the classical ‘‘pozzolanic’’ reaction. especially where sufficient time is available for these slow reactions to take place. Biomass ash does not contain toxic metals like in the case of coal ash. ilite. its chemical and physical characteristics must be suitable for that purpose. The principal components of bituminous coal fly ash are silica.1 to 3. the consistency and predictability being as important as the numerical values of the various parameters involved. Fly ash. Such factors as glass content. as expressed in the usual oxide convention. The chemical characteristics of fly ash are secondary. the low-calcium Class F fly ash is commonly produced from the burning of higher-rank coals (bituminous coals or anthracites) that are pozzolanic in nature (hardening when reacted with Ca(OH)2 and water). Uniformity and chemical consistency from day to day and week to week is the prime necessity. it is evident that lignite and sub-bituminous coal fly ash has a higher calcium oxide content and lower loss of ignition than fly ash from bituminous coals. The only real chemical requirement is that fly ash has a sufficient content of glass that eventually will react with added lime. while its specific surface area may vary from 170 to 1000 m2/kg [8– 11]. From the table. bituminous. as measured by the loss on ignition (LOI). iron oxide. mostly in the form of calcium hydroxide. since little or no adjustment can be provided at the concrete mixing stage. and iron content in the ash. The ash . may actually be beneficial in cement raw material use. Lignite and sub-bituminous coal fly ash may have a higher concentration of sulphate compounds than bituminous coal fly ash. Stabilization of some base courses (and stabilized sub grades) may rest on lime fly ash chemical reactions. conditioned. The specific gravity of fly ash usually ranges from 2. although not in an important way. Chemical properties The chemical properties of fly ash are influenced to a great extent by the properties of the coal being burned and the techniques used for handling and storage. alumina. and possibilities for developing efflorescence. According to the American Society for Testing Materials (ASTM C618) [12]. Table 1 Normal range of chemical composition for fly ash produced from different coal types. Another difference between Class F and Class C is that the amount of alkalis (combined sodium and potassium). with lime. or wet form.e. total calcium typically ranges from 1 to 12%. Even high carbon content. The success of fly ash in structural fill applications rests primarily on the ability of the material to be compacted to a reasonably strong layer of low unit weight.0. which depends on the geological factors related to the formation and deposition of coal. Ahmaruzzaman / Progress in Energy and Combustion Science 36 (2010) 327–363 is also silt-sized. Properties of biomass ash The use of biomass as fuel generates large amount of residual ash which causes serious environmental problems. The chief difference between Class F and Class C fly ash is in the amount of calcium and the silica. each vary in heating value. depending on the amount of unburned carbon in the ash. or ranks. the ash containing more than 70 wt% SiO2 þ Al2O3 þ Fe2O3 and being low in lime are defined as class F. Low-calcium fly ash may be entirely satisfactory or even preferred. and sideraete. The less predominant minerals in the unreacted coals include calcite. and geological origin. compared with bituminous coal fly ash. On the other hand. are generally higher in the Class C fly ash than in the Class F fly ash. sub-bituminous. Since the blended cement manufacturer has little control over the concurrent use of chemical admixtures or of mixing and curing conditions. since it provides a definite (although modest) proportion of the fuel needed. the requirements differ considerably depending on the specific end use involved. With highway bases chemical considerations come into play. Briefly. The cement and concrete end-use areas are by far the most demanding of the fly ash in terms of adherence to strict criteria and requirements. are relatively immaterial. 2. However. CS and C4AS. so there are only small amounts of anthracite coal fly ash. as well as lower carbon content.2. and glassy components. ash content. Quartz and mullite are the major crystalline constituents of low-calcium ash. There are basically four types. and calcium. Fly ash for use as a raw material in cement manufacture is sold and used primarily on the basis of its chemical composition. and sulphates (SO4). the type of crystalline matter present. In Class F fly ash. can be established by X-ray diffraction (XRD) analysis.%) Bituminous Sub-bituminous Lignite SiO2 Al2O3 Fe2O3 CaO MgO SO3 Na2O K2O LOI 20–60 5–35 10–40 1–12 0–5 0–4 0–4 0–3 0–15 40–60 20–30 4–10 5–30 1–6 0–2 0–2 0–4 0–3 15–45 10–25 4–15 15–40 3–10 0–10 0–6 0–4 0–5 The mineralogical composition of fly ash. C3A. and lignite. This is primarily a function of particle size distribution. its combustion conditions. pyrite and hematite. In contrast. size distribution. calcium sulphate. fly ash for use in blended cements must be of consistent and uniform chemical and physical characteristics. of coal. The four types (ranks) of coal are anthracite. and presence of unburnt material play an important role in determining the application. however. Some of the spent absorbent discharged from the desulfurization process can be used as the raw material for the absorbent pellets. Adsorbents for cleaning of flue gas 5. Na. an absorbent feeder and a drawout facility. As a class. Typically. 1. However. raw material for ceramics. but are not limited to. addition to construction materials as a light weight aggregate. which depends on the varieties of origin from woody to herbaceous and other resources [14. Many kinds of biomass fly ash have similar pozzolanic properties as coal fly ash. furthermore. wood. wheat straw and sugar cane straw [19–21] among which have been added in concrete as mineral admixtures. commercial utilisation of biomass ash is not widely reported. water and environmental improvement. this spent absorbent is reused as a solidification agent for sludge and as a deodorant for refrigerators. However. type of soil and harvesting [13]. Fly ash treated with calcium hydroxide has been tested as a reactive adsorbent for SO2 removal [24]. even for the same type of biomass. biomass fly ash varies more than coal fly ash.g. season. pet litter and so on [23].18]. such as those from rice husk. adsorbent. While the elemental composition of the ash is determined by the inorganic constituents in the parent biomass. NO D 1=2 O2 / NO2 (1) SO2 D NO2 / SO3 D NO (2) CaðOHÞ2 D SO3 / CaSO4 D H2 O (3) As shown in the above chemical formulas. Dry-type FGD does not require wastewater treatment. Schematic plant view of flue gas desulfurization using coal ash [23]. secondly. however. Rice husk with its high silica content has been used as an insulator. improving the performance of concrete. Si and P and some of these act as important nutrients for the biomass [14]. the properties of its fly ash depends also on some growth and production factors including weather.16]. can be in the form of an alternative to another industrial resource. they are fixed as sulfite in other conventional dry processes such as limestone injection and active manganese. Ahmaruzzaman / Progress in Energy and Combustion Science 36 (2010) 327–363 forming constituents in biomass fuels are quite diverse depending on the type of biomass. A simplified plan view is shown in Fig. 4. addition to cement and concrete products. storage and geographic origins [16. 1. there may be financial returns from the sale of the by-product or at least an offset of the processing and disposal costs. The process flow is explained as follows: the system is composed of an absorber body. etc. Both absorption and removal in sulfur dioxide are conducted during the time when the absorbents move down from the upper part to the lower part of the absorber. rice husk) while some have high alkali metal content (wood).1. The following is a brief description of each of the previously mentioned alternative uses of fly ash and associated research that has been conducted and how it relates to each alternative use.M. the major ash forming inorganic elements in biomass fuels are Ca. Studies on ash from arecanut shell. These processes and applications include. fly ash from neat biomass combustion has more alkali (Na and K) and less alumina (Al2O3) than coal fly ash [13. namely fly ash.17]. it is too costly for large-scale environmental remediation applications. Flue gas containing sulfur dioxide is introduced to the absorber to make contact with the absorbents. Fly ash recycling in the flue gas desulphurization process has shown promising results. it requires a large amount of absorbent compared to wet-type FGD. However. Bagasse fly ash has been examined as an adsorbent as well as an additive in cement and concrete [19–21]. and fourthly. such as high water consumption and the need for wastewater treatment [6]. structural fill and cover material. On the other hand. Coal fly ash is a cheap absorbent for dry-type FGD. the by-products can replace some scarce or expensive natural resources. Sulphur compounds Effort has been made to reduce SOx emissions by installing equipment for flue gas desulphurization (FGD). cashewnut shell and groundnut shell ash are limited [21]. However. In addition. 331 5. K. thirdly. Activated carbon was used to oxidize reduced sulphur compounds. material recovery. Therefore. roadway and pavement utilization. surface area. In this section. the application of fly ash has been discussed. the sulfur dioxides in the flue gas are fixed as gypsum. cement and concrete additive and as a substitute for silica [22]. The absorbents in a fixed process are fed into an absorber and drawn out of its lower part. or application. and soil. The reactions are represented below. The wet-type limestone scrubbing processes is widely used because of its high DeSOx efficiency and easy operation.15]. its high carbon content can cause a hindrance in its application for concrete. Compared to coal fly ash where significant research has already taken place and high utilisation figures are already reported in several countries [16. The composition. infiltration barrier and underground void filling. the crystallinity and mineralogy depends on the combustion technique used. . thus enabling other uses of the land and decreasing disposal permitting requirements. less area is reserved for disposal. process. In general. and an absorbent manufacturing facility. these processes have drawbacks. Utilization of coal combustion by-products. some biomass fuels have high silicon content (e. This may be due to the fact that a higher molar ratio of calcium to-sulphur is required to obtain a high DeSOx efficiency. based on its characteristics. Fly ash utilization There are many reasons to increase the amount of fly ash being re-utilized. cement and concrete additive. A few of these reasons are given below. A mixture of fly ash and calcium hydroxide for Fig. disposal costs are minimized. several research efforts are underway for applications such as adsorbent. biomass fuels exhibit more variation in both composition and amount of inorganic material than is typical of coal. and then the treated gas is discharged from a stack to the atmosphere [23]. Firstly. it emits carbon dioxide (greenhouse gas) into the atmosphere as follows. caps have been established on the emission of nitrogen oxides (NOx). considerable attention has been paid to the capture of mercury by unburned fly ash carbons [35–42]. this mixture exhibited similar characteristics to typical activated carbon for flue gases. with the introduction of the 1990 Clean Air Act Amendments. The mercury values recorded were compared to the content of each type of organic component and total inorganic matter present in the fly ash. It was found that Ca(OH)2-fly ash mixtures were a low-cost SO2 control option. Because mercury accumulates in the biosystem it is of particular concern. It can be seen that the fly ash exhibit different retention capacities depending on the species in gas phase (Hg0 or HgCl2). but this FGD has not yet spread worldwide. activated carbon injection is the process most promising for removing mercury from flue gas. However. Removal of mercury Mercury has long been known as a potential hazard to-health and environmental hazard.2. due to technical and economic limitations. after adsorption. it is desirable to find an alternative carbon. any practical application of such material would be economically and environmentally advantageous to the overall fly ash beneficiation process. with a particulate matter control device. to replace costly activated carbons. there is no need for wastewater treatment or gas reheating. Carbon-rich fractions from a gasifier were adsorbed one-third of the NOx compared with a commercial carbon. captured [35. and mainly wet-type limestone FGD units have been installed [28]. The FGD process using coal ash has been commercialized. Many coal-fired utilities have begun to retrofit with low NOx burners to meet the emission requirements. During operation. and it. CaCO3 ðslurryÞDSO2 D 1=2 O2 / CaSO4 ðslurryÞ D CO2 (4) Dry-type FGD using fly ash is one of the processes that provide a solution to the above-mentioned problems. and the carbon can be activated to further improve the adsorption performance of the fly ash. The retention of hazardous elements by fly ash produced in combustion plants has been extensively studied in recent years. Usually the unburned carbon content in fly ash is in the range of 2–12%.3. Recently.000 MW per year. 5. and is high in the public awareness. It was found that mineral matter must be removed efficiently from unburnt carbon of fly ash before activation. and so this process is considered to be an ideal choice for controlling the emission of sulfur dioxide and an environmentally friendly method for reuse of coal ash. 5.42. Because mercury retention depends on the mode of occurrence of this element in gas phase the evaluation was based on each individual mercury species. isotropic coke (isotropic fly ash carbons) to anisotropic coke (anisotropic fly ash carbons) [37]. The role that the different types of unburned carbons play in mercury capture in fly ash has also been a matter of interest for some studies associating types of particles with the amount of Hg.26]. As described in this part. no process has been commercially utilized beyond pilot scale tests. the carbon content of fly ash increases significantly.46–48]. Since the introduction of FGD in the late 1960s.2) [23]. [49] have tried to establish a relationship between Hg0 and HgCl2 retention and the characteristics of fly ash samples taken from the combustion of feed coal blends of different characteristics. activated carbon from unburned carbon in coal fly ash has also been used for removal of NO [32].43–45]. this carbon present in fly ash can be a precursor of activated carbons since it has gone through devolatilization during combustion in the power station furnace. Although the role of inorganic components of fly ash in this capture is still unclear. such as the Ebetsu power station (50. The properties of fly ash – particularly with respect to NOx adsorption – were closely examined for carbon content and specific surface area. To cope with the mercury emission problem. the BET (Bruner Emmett Taylor) surface area and the quantities of mercury retained was studied. The relationship between the types of particles. Lo´pezAnto´n et al. Davini [27] also tested a process using activated carbon derived from fly ash for SO2 and NOx adsorption from industrial flue gas.43]. global market demand for FGD has been steady at between 5000 and 10. Since the unburned carbon separated from fly ash is a by-product.43]. The exact nature of Hg–fly ash interactions is still unknown and the variables affecting the mercury adsorption need to be identified. When the retention of Hg0 was . given that the BET surface area successively increased from inertinite. It was found that unburned carbon remaining in the fly ash particles contribute the main surface area to fly ash. Furthermore.000 Nm3/h) under a high molar ratio of calcium to sulfur (1. A comparison of the results obtained demonstrates that Hg0 is retained in fly ash in a greater proportion than HgCl2. such as utility flue gas. therefore. Adsorption of NOx Fly ash has also been proposed as adsorbents for NOx removal from flue gases [29]. The adsorption of NOx using activated chars recovered from fly ash was reported [31]. activated carbon powder is injected into the flue gas stream and collected. requires only a process of activation [30]. In view of the significant variations in the properties of fly ash obtained from different coals [43. it is very difficult to monitor and capture. and to better understand the properties of the materials influencing the capture of Hg. As a result of such transition. the high cost of activated carbon hinders large-scale applications in utility boilers [33]. Ahmaruzzaman / Progress in Energy and Combustion Science 36 (2010) 327–363 desulphurization was also studied by Davini [25. Among the current technologies being evaluated. When the raw fly ash samples are compared with the fractions enriched in unburned carbons it can be observed that retention capacity increases slightly as the unburned carbon content (LOI) increased. due to the low oxygen and/or low temperature combustion conditions required by those low NOx combustion units. The concentration of unburned carbons and their respective ability to capture Hg have also been related to their textural properties [37. However. Experimental results on activating coarser fly ash particles showed that adsorption capacity can be increased through controlled gasification of the unburned carbon. efforts have been made to remove various types of mercury from the flue gas of utility boilers.000 Nm3/h) and the Tomtoh Atsuma power station (644. So. due to its high removal efficiency. A relationship has been reported between Hg content and the percentage of carbon in fly ash derived from the combustion of bituminous coals [37] and coal blends containing anthracites [42. In the case of mercury it has been observed that some fly ash may capture this element which would otherwise be emitted into the atmosphere. wet limestone FGD requires a wastewater treatment facility. to obtain a more suitable activated carbon for environmental applications in the gas phase. it is identified as one of the 189 toxic air pollutants by the Clean Air Act Amendments of 1990. up to 20% in some cases. However. and some industrial plants have achieved DeSOx efficiencies of over 90%. Such findings triggered the idea of using fly ash carbon as a low-cost adsorbent in removing elemental mercury from gas phases.332 M.0–1. Researchers at The Pennsylvania State University have developed a method to economically separate unburned coal from fly ash [34]. Preliminary study shows that some unburned carbon from fly ash has certain capabilities for adsorbing elemental mercury. In this process. 03 30–60 30–60 30–60 20 20 30–50 [81] Fly ash 52.5–249. Generally. Adsorption of gaseous organics Apart from the adsorption of NOx.9 6. and its physical properties such as porosity.M. calcium oxide.3 7.3 205.64 0.75 3.08–0.3 1.6 0.8 0.18 1.5 7.16 1. which is also suggested by Hall et al.2 180.67–0.19 0.24–2. Removal of toxic metals from wastewater Fly ash has potential application in wastewater treatment because of its major chemical components.40–0.4.39 1.8 198. ion exchange.1 126. Moreover. Pb2þ Cu 2þ 6. The fly ash samples that have a greater surface area retain a higher quantity of HgCl2. The adsorption of toluene vapours on fly ash was investigated by Peloso et al.76 7.068–0.26–2.35 0. in order to maximise metal adsorption by hydrous oxides.5–15.03 11.5–13.83 0.63–0. called primary sites.61 25 25 25 32 30–50 Fly ash Fly ash þ wollastonite Fly ash Fly ash (I) Fly ash (II) Fly ash Fly ash-washed Fly ash-acid Fly ash Bagasse fly ash Fly ash Fly ash Coal fly ash Fly ash CFA CFA-600 CFA–NAOH 1. It was assumed that the complex chemical action with activated carbon and calcium chloride was most significant for metallic mercury removal by actual fly ash.4 1.30 7. [52] utilized synthetic fly ash.98 0.1 76. No increase in adsorption rates was observed with increased temperature. When a molecule of the adsorbate adsorbs on a primary site. The removal of mercury was affected by temperature.0 12.12–1.81 2.8 18.05 18.36 0.25–1.38 25 25 25 – 20 20 20 20 30–50 25 25 [79] Fly ash Fly ash-washed Fly ash-acid Fly ash Bagasse fly ash Fly ash Fly ash Treated rice husk ash 444. Table 2 Summary of adsorption of metals on fly ash. chemical precipitation.6–106. The enhancement of mercury adsorption after oxidizing unburned carbon at 400 C in air shows that oxygen-containing functional groups may have an important role.4 5. solvent extraction. fused and porous structures (which are mainly network structures in all cases).21 6.98 3. the adsorbed molecule can then act as a secondary center for the adsorption of more molecules.04 0. This suggested that adsorption was diffusion-controlled. magnesium oxide and carbon. [51].1 30 30 – 20 20 25 25 25 25 30–50 32 – 25 Fly ash Fe impregnated fly ash Al impregnated fly ash Fly ash(I) Fly ash(II) Bagasse fly ash Fly ash Bagasse fly ash Fly ash 9. the alkaline nature of fly ash makes it a good neutralising agent.27 0. The results indicated that the kinetics of mxylene adsorption by fly ash resembled kinetics reported for penetration of absorbates into porous adsorbents. becoming a severe public health problem.92 7.34–2.22 1.29 0. no correlations were found.88 7. which showed very high efficiency of over 99% for mercury removal at 120 C.70 3.11 14. consisting of calcium chloride with 5% activated carbon.4 20–40 [65] Cd2þ 5.0 95.09–1. It was found that fly ash product obtained after particle aggregation and thermal activation showed satisfactory adsorption performance for toluene vapours [54].4 0. Among these processes.0 0. Ahmaruzzaman / Progress in Energy and Combustion Science 36 (2010) 327–363 compared to the amount of each type of unburned carbons in the fly ash. 333 Ni2þ Cr3þ [83] [84] [93] [94] [104] [105] [106] [87] [86] [85] [71] [63] [71] [80] [83] [85] [95] [105] [70] [86] [64] [85] [79] [68] 30 30–60 30–60 30–60 [79] [92] [87] [75] [73] [68] [80] [84] [79] [69] [93] [100] [87] [70] [75] [74] [84] [95] [87] [85] [67] (continued on next page) . mercury vapor was completely removed.25–2. However.30 2. if the activated carbon content was very small.4–214. but this tendency shows several exceptions in the case of Hg. particle size distribution and surface area. However. [53].0077–0.57].5 0. a general tendency could be observed with the anisotropic.0–15.7–137.7 483.1 0.34–1.0 753 285–566 18.21 4. the adsorption process may be a simple and effective technique for the removal of heavy metals from wastewater. it is necessary to adjust the pH of wastewater using lime and sodium hydroxide [56.25 207. The adsorption of mercury on carbon can be explained by the physical and chemical interactions which occur between the carbon surface and mercury. on fly ash has also been studied [55]. ferric oxide.0 178. silica. reverse osmosis or adsorption etc.5 20.0 9. fly ash has also been used for adsorption of organic gas.84 30–60 30–60 30–60 20 20 20 30–50 30 23 25 0–55 – [81] Fly ash Fly ash-washed Fly ash-acid Fly ash Fly ash zeolite Fly ash Fly ash (I) Fly ash (II) Bagasse fly ash Fly ash Coal fly ash Rice husk ash Afsin-Elbistan fly ash Seyitomer fly ash Bagasse fly ash Fly ash Fly ash 198. When the calcium chloride content was more than 0.0–14.75 0.54 13.4 437.19 207.06–1. which are alumina.8–14.07–1. According to the theory proposed by Dubini [50] the carbon surface contains some adsorption centers. Metals Adsorbent Adsorption Temperature ( C) References capacity (mg/g) Zn2þ Coal fly ash Fe impregnated fly ash Al impregnated fly ash Coal fly ash Coal fly ash(I) Coal fly ash(II) Bagasse fly ash Bagasse fly ash Fly ash Fly ash Fly ash Fly ash Rice husk ash Bagasse fly ash Fly ash Rice husk ash Fly ash 6.93 10–15. Heavy metal and metalloid removal from aqueous solutions is commonly carried out by several processes such as. heavy metals are most serious pollutants. and rate constants decreased with increased vapour pressure. The adsorption kinetics of representative aromatic hydrocarbon and m-xylene.6–8.48 0.5% in the synthetic fly ash with 5% activated carbon. the most efficient removal was obtained when the activated carbon content ranged from 5 to 7% in synthetic fly ash with 1% calcium chloride.2 195. Today. SOx and mercury in flue gas.29 0. Masaki et al.7–8. 0 12. Equilibrium studies for the adsorption of zinc and copper from aqueous solutions were carried out using sugar beet pulp and fly ash [71].63–0. Fly ash was also found to be effective for the removal of mercury. complexation of heavy metals and humic acid plays an important role. contact time.86 25. Gangoli et al. respectively. respectively. The use of fly ash for removal of heavy metals was reported as early as 1975. Alkaline aqueous medium favors the removal of Cd(II) by fly ash. The presence of high ionic strength or appreciable quantities of calcium and chloride ions does not have a significant effect on the adsorption of these metals by fly ash. The carbon fraction in fly ash was important in the removal of Cu(II). The finer the rice husk ash particles used.92 and 18.8 0.1. Pb(II) and Cu(II) adsorption can increase to 37 and 28 mg/g. Its adsorption capability and adsorption rate are considerably higher and faster for Pb(II) than for Hg(II). Mg. Changing the nature of CFA did not improve its ability to adsorb Cu(II). The process of removal follows first order adsorption kinetics and the rate controlling step is intraparticle transport into the pores of fly ash particles. Raw bagasse and coal fly ash have also been used as low-cost adsorbents for the removal of chromium and nickel from aqueous solutions [67].6 kJ mol1) were consistent with an ion exchange adsorption mechanism.73 6. The removal of Cd(II) has been found to be contact time.334 M. For Pb–HA and Cu–HA systems. Ca. The effectiveness of fly ash in adsorbing mercury from wastewater has been studied [77].67 0.02–34. Pb. Fly ash can also be shaped into pellets and used for the removal of copper and cadmium ions from aqueous solutions [70]. The presence of humic acid in water will provide additional binding sites for heavy metals. The effects of chromium concentrations. [58] reported the utilization of fly ash for the removal heavy metals from industrial wastewaters. concentration. i. temperature and pH.55 0. The utilization of rice husk ash was investigated for the adsorption of Pb(II) and Hg(II) from aqueous water [73]. for a single pollutant system. Fly ash with different quantities of carbon and minerals was also used for removal of Cu(II) from an aqueous solution [69].98 mg/g. the values of activation energy (between 1. Raw and modified coal fly ash effectively adsorbs Cu(II) from wastewater [74]. The calculated adsorption capacities for copper and cadmium were found to be 20. The kinetics of adsorption indicated the process to be diffusion controlled.82 11. Selective adsorption of various metal ions (Na. A homogeneous mixture of fly ash and wollastonite (1:1) was also reported to remove Cr(VI) from aqueous solutions by adsorption [61]. Among these metal ions. Bhattacharya et al. [75] investigated the competitive adsorption of heavy metals and humic acid using fly ash as adsorbent.4 5. . Similar results on the adsorption of Cd and Cu by fly ash were also reported [80]. The adsorptions of Cu(II) onto coal fly ash (CFA). Cu. Pb(II) and Cd(II) from water [79].31 23. adsorbate and experimental system. The lime (crystalline CaO) content in the fly ash seemed to be a significant factor influencing the adsorption of Cr(VI) and Cd(II). Mn. The adsorption sequence is Cu > Pb > Cd in accordance with the order of insolubility of the corresponding metal hydroxides. fly ash can achieve adsorption of lead ion at 18 mg/g. Turkish fly ash was also used for the removal of Cr(VI) and Cd(II) from an aqueous solution on [64]. Ni. Lead ions were found to be selectively adsorbed at a mean value of 19 meq of Pb(II) per 100 g of fly ash. For co-adsorption. Fly ash was found to have a higher adsorption capacity for Cd(II). and Fe) by fly ash was also reported [78].8 mg Cu/g carbon. by rice husk ash. Coal fly ash has also been used for the removal of toxic heavy metals. potassium nitrate solution.92 0.7–89. The presence of organic pollutants significantly affected the removal of heavy metals from wastewater. The breakthrough volumes of the heavy metal solutions have been measured by dynamic column experiments in order to determine the saturation capacities of the adsorbents. Cr. respectively. K.2 7. while the capacities for mineral were only about 0.2 0. Cd.64 1. This selective adsorption could be due to the formation of crystalline ettringite mineral after the hydration of the fly ash. The heavy metal ions present in the system will compete with the adsorption of humic acid on fly ash.38 1. Wang et al. including Cr(VI) and Cr(III) using fly ash has been investigated by several researchers [59.5 30 30–60 30–60 30–60 30 30 5–21 30 25 20 25 [76] [82] Hg2þ As3þ As5þ [62] [82] [85] [85] [97] [87] [87] [77] [73] [109] [107] [109] 6.82 1. copper ion at 7 mg/g and humic acid at 36 mg/g.5 13.72 3. and pH on the removal of chromium were reported. as compared to Cr(VI). [66] investigated the removal of cadmium by fly ash by varying contact time. The temperature dependence of Cd(II) adsorption on fly ash indicates the exothermic nature of adsorption. and CFA– NaOH followed pseudo-second order kinetics. Removal of chromium ions.0 3.3 and 9.e. The specific adsorption capacities of carbon ranged from 2.63] studied the removal of Cr(VI) and Zn (II) from aqueous solution using fly ash. the higher the pH of the solution and the lower the concentration of the supporting electrolyte. Removal efficiency was found to be dependent on concentration. As.2 to 2. pH and temperature [68]. Table 2 summarizes the results of the important metals investigated using fly ash. The Bangham equation can be used to express the mechanism for adsorption of Pb(II) and Hg(II). [62. Yadava et al. Fly ash was also utilized for the removal of copper from aqueous solution. The extent of adsorption at equilibrium was found to be dependent on the physical and chemical characteristics of the adsorbent. thus resulting in a decrease in humic acid adsorption. Ahmaruzzaman / Progress in Energy and Combustion Science 36 (2010) 327–363 Table 2 (continued ) Metals Adsorbent Adsorption Temperature ( C) References capacity (mg/g) Cr6þ Fly ash þ wollastonite Fly ash þ China clay Fly ash Rice husk Ash Fly ash Fe impregnated fly ash Al impregnated fly ash Fly ash(I) Fly ash(II) Bagasse fly ash 2. Cu. temperature and pH dependent. thus promoting metal adsorption on fly ash. The removal characteristics of Pb(II) and Cu(II) from aqueous solution by fly ash were investigated by Alinnor [72]. fly ash dosage.63– 0. Cu(II). The adsorption capacity of coal fly ash for mercury was comparable to that of activated powdered charcoal [76].81 mg Cu/g mineral. It is found that.35 – – – – 30–60 30–60 30–60 20 20 30–50 [61] Fly ash Fly ash Fe impregnated fly ash Al impregnated fly ash Sulfo-calcic Silico-aluminous ashes Fly ash-C Treated rice husk ash Fly ash coal-char Fly ash Fly ash coal-char 2. CFA-600.7–27. Cd and Hg are the most often investigated. The increase in adsorption of Cd(II) with pH has been explained on the basis of surface complex formation approach. These adsorptions were endothermic in nature. Pb. Adsorption of various types of heavy metals on fly ash Fly ash has been widely used as a low-cost adsorbent for the removal of heavy metal. Hg. It was found that fly ash shaped into pellets could be considered as a potential adsorbent for the removal of copper and cadmium from wastewaters.60]. the more Pb(II) and Hg(II) absorbed on rice husk ash. Cr. Fly ash obtained from the combustion of poultry litter was also utilized as an adsorbent for the removal of Cr(III) from aqueous solution [65].25–4.82 4. Formation of calcium silicate hydrates (CSH) was assumed to be responsible for increasing removal.88]. were tested to remove Pb(II). Cr(VI) [89] and Hg(II) [90] from aqueous solutions.667 mg/g and that of Hg(II) was 11. respectively.5 mL/min. and found that fly ash was effective as activated carbon. surface complex formation. 6. Fly ash removed Cu and Pb from the effluent. Bayat investigated the removal of Zn(II) and Cd(II) [83]. The effectiveness of fly ash as an adsorbent improved with increased calcium content (CaO). the removal of these toxic heavy metals resulted in a reduction of toxicity. The last step is an equilibrium reaction. Adsorption mechanism and kinetics For a solid liquid adsorption process. was investigated by Huang research group [104–106]. in dynamic column experiments. [102] reported that fly ash showed good adsorptive properties for removal of lead. India. Pb(II).86]. Gupta and Terres [91] measured the changes in toxicity and heavy metals in a municipal wastewater treatment plant effluent by treatment with fly ash. Mercury is bound to the ash surface due to several chemical reactions between mercury and various oxides (silicon.5.2–4.2. The percentage of adsorbed ions was greater when they were in contact with silico-aluminous fly ash than sulfo-calcic fly ash. The cation exchange capacity and specific surface area of fly ash increased with increased carbon content. Ni(II). Lead and chromium are also adsorbed by the developed adsorbent up to 96–98%. solute diffusion into pore of adsorbent except for a small quantity of sorption on external surface. The batch test showed 90% removal for Cd and Ni. except in the case of the ion Ni(II). using bagasse fly ash as adsorbents. while the arsenic concentration was reduced from 500 to <5 ppb. nickel [95] and chromium [96. dosage of fly ash and temperature. They used bagasse fly ash from sugar industries for the removal of lead [92]. The primary mechanisms of copper removal by SSA included electrostatic attraction. Cd(II). Retention of cesium sharply drops with ionic strength. respectively). Adsorption of radiocesium is maximum around neutral region. Cr(III). obtained from coal power stations. The adsorption dynamics can be described by the following three consecutive steps: transport of solute from bulk solution through liquid film to adsorbent exterior surface. especially above pH 8. Kinetic and equilibrium experiments were performed to evaluate As(V) removal efficiency by lignite-based fly ash. and 1. Ni(II) and Cu(II) [84]. derived from fly ash is compared with those of commercially activated carbon [109]. loading.40 mg/g. Zn. the effluent showed a significant reduction in toxicity. This is because the amounts of adsorption or ion exchange sites on carbon soot are higher than on mineral surface. The adsorption capacity of FA. Consequently. The percent adsorption of Zn(II) and Cd(II) increased with an increase in concentration of Zn(II) and Cd(II). The adsorption of 335 metal ions onto the surface of fly ash was found to be proportional to the carbon contents. Ni(II) and Zn(II). cadmium. and 13. whereas radiostrontium adsorption increases with pH.97] from aqueous solutions. The extent of removal was achieved in the order of Pb(II) > Cu(II) > Ni(II) > Zn(II) > Cd(II). indicating that the process is exothermic in nature. on the surface of the ash. After the treatment with fly ash. and for decreasing desorption. The efficiency of removal of As(V) and As(III) on charcarbon (CC).379. Copper and zinc are adsorbed by the developed adsorbent up to 90–95% in batch and column experiments. maximum adsorption occurred in the pH range of 7. The removal of these two metal ions (up to 95–96%). Adsorption of Cd (I). Cu.100]. The precipitation of copper hydroxide occurred only when the dosage of SSA and the equilibrium pH of wastewater were at a high level (30/40 g/l and greater than 6. using fly ash adsorption and cement fixation of the metal-laden adsorbent.12. 1. showed that removal was in the following order: Pb > Zn > Cu > Cr > Cd > Co > Ni > Mn [103]. Bagasse fly ash and rice husk ash were also utilized for the removal of Ni(II). Suggested mechanism of retention of radionuclide by fly ash is specific adsorption of Cs (I). The Gupta research group conducted a series of investigations on the adsorption of heavy metals. carbon residual in the fly ash play a more important role than mineral matter in the removal of metals by the fly ash. The removal of Zn is 100% at low concentrations. Fly ash. The impregnated fly ash showed much higher adsorption capacity for all the ions. copper and zinc [93. at least for Zn(II) and Cd(II) in dilute industrial wastewaters.94]. Fly ash was also effective for the removal of arsenic from aqueous solution. A 10% metal-laden fly ash was tested for leaching and it exhibited metal concentrations lower than the drinking water standards. Static tests removed 80% arsenic. compared to Cr(VI). The adsorption isotherm of SSA for copper ions generally followed the Langmuir model and depends on particle size. Ni(II). Cu(II).Cd(II) and Zn(II) from an aqueous solution [85. as compared to that of untreated fly ash. using lignite-based fly ash and activated carbon. Gashi et al. using fly ash on wastewater at Varnasi. Ahmaruzzaman / Progress in Energy and Combustion Science 36 (2010) 327–363 Banerjee et al.820. in about 60 and 80 min. The adsorption capacities of sewage sludge ash (SSA). Fly ash and fly ash/lime mixture were investigated for the removal of Cu. and cation exchange.00. and irreversible ion exchange uptake of Sr(II). parallel to this is intraparticle transport mechanism of surface diffusion. [60. with fly ash for copper ions were compared [98].50. aluminium and calcium silicate).1 mg/g close to that of fly ash. Zn(II). This is consistent with cation exchange capacity and specific surface area. Adsorption studies carried out to estimate heavy metal removal. Results showed that fly ash could be an effective metal adsorbent. Removal efficiencies were greater than 70%. Fly ash was found to be good adsorbent for removal of zinc from aqueous solutions [101]. was achieved by column experiments at a flow rate of 0. was examined for removal of As (V) from water [107]. and adsorption of solute on interior surfaces of the pores and capillary spaces of adsorbent. The uptake decreases with increased temperature. silico-aluminous fly ash and sulfo-calcic fly ash. Al–FA. The overall rate of adsorption will . Maple wood ash without any chemical treatment was utilized to remediate As(III) and As(V) from contaminated aqueous streams in low concentrations [108]. A process for the treatment of industrial wastewater containing heavy metals. the third step is rapid and negligible. Cd and Pb [87. whereas removal is 60–65% at higher concentrations. pH etc. studied the adsorption of various toxic metal ions. Of the three steps.61]. It was reported that coal fly ash is a good adsorbent for both radionuclides of 137Cs and 90Sr [110]. the solute transfer is usually characterized by either external mass transfer (boundary layer diffusion) or intraparticle diffusion or both.M. on fly ash and Al and Fe impregnated fly ash. and Fe–FA for Cr(VI) was found to be 1. zinc. Ni. The estimated maximum capacity of copper adsorbed by SSA was 3. respectively.2. whereas the adsorption of strontium increases sharply and steadily at low and moderate concentrations of inert electrolyte. Cr(II) and Hg(II)]. Zn(II) and Ag(I) on fly ash was investigated and found that the process was spontaneous and endothermic [104]. Fly ash was found to have a higher adsorption capacity for Cd(II). Pb and PO43 and NO 3 contents.0– 7. cadmium and copper from effluents in the battery and fertilizer industries. Two fluidized-bed-sourced fly ashes with different chemical compositions.The feasibility of using fly ash for the removal of Cu(II) and Pb(II) from wastewater was investigated [99. Sips model suggests that the equilibrium data follow Freundlich curve at lower solute concentration and follows Langmuir pattern at higher solute concentration. which are expressed in Eqs. as it contains the heterogeneity factor b.81. the parameters A. which is an (14) This isotherm describes adsorption on heterogeneous surfaces. Adsorption kinetics of heavy metals on fly ash was investigated by several researchers. m is the mass of the adsorbent. A linear plot from Eq. a straight line will be obtained. (14). Kelleher et al. B and b. ks and ki are the pseudo-first order. Cs and Ct are surface and solution concentration. Kf is the measure of sorption capacity. Langmuir model can describe most adsorption phenomena of heavy metals on fly ash [76. the pseudosecond order kinetics. and the values. Freundlich. x 1=n log ¼ logKf þ logCe m where. In most cases. For a single solute. it is given by x Vm KCe ¼ m 1 þ KCe (9) However. The constant B is related to the heat of adsorption [111]. It can reduce to Langmuir equation as b approaches one.82].97]. Using Eq. Vm and K for isotherms of the metal under study can be obtained. pseudo-second order rate constant.82. Most investigations reported that adsorption of metal usually follows the first order kinetics [68. mass transfer coefficient. The Tempkin isotherm has been used in the following form: qe ¼ RT=bðlnACe Þ (18) Eq. The Freundlich model. Dubinin–Kaganer– Radushkevich (DKR). and that adsorption is pore diffusion controlled [68.81. b (mol2/J2) is a constant related to the adsorption energy. Qe is the amount adsorbed (mol/gm). The DKR equation can be represented as ln Qe ¼ ln Qm b32 (15) where. Tempkin.84. and S is the specific surface area. external diffusion model. When lnQe was plotted against e2.The equation is represented below: Ce B 1 ¼ þ Ceb x=m A A The Langmuir.91]. (10) can be drawn for a particular metal adsorption. (18) can be expressed in its linear form as: qe ¼ RT=blnA þ RT=blnCe (19) B ¼ RT=b (20) A plot of qe versus ln Ce enables the determination of the constants A and B. The value of b is related to the adsorption energy. and kinetic studies suggested that overall rate of adsorption was pseudo-second order. (13).77. B. by using least squares method. A.95. Various kinetic models have been suggested for adsorption. (5)–(8) as listed below: logðqe qt Þ ¼ logqe empirical model used to describe adsorption in aqueous systems. and rate parameter of the intraparticle diffusion control stage. Vm and K increase with temperature. x/m is the amount adsorbed per unit mass of adsorbent. q is the heat of adsorption. Redlich–Peterson.3. and e is the Polanyi potential. was also used to explain the observed phenomena of adsorption of metal on fly ash materials. Ahmaruzzaman / Progress in Energy and Combustion Science 36 (2010) 327–363 be controlled by the slowest step that would be either film diffusion or pore diffusion controlled. Vm is the monolayer capacity. x 1=n ¼ Kf Ce m (12) The linear form of the equation can be written as: k1 t 2:303 (5) t 1 1 ¼ þ t qt k2 q2e qe (6) dCt ¼ ks SðCt Cs Þ dt (7) qt ¼ ki t 1=2 (8) where k1. E. the linear form of the equation can be written as Ce 1 Ce þ ¼ x=m KVm Vm (10) Where Ce is the equilibrium concentration of the solution.83. The equation can be represented as follows [112]: Q ¼ ðKs Ce Þb=½1 þ ðas Ce Þb (21) . suggesting that adsorption capacity and intensity of adsorption are enhanced a higher temperature. The Freundlich isotherm is shown in the following equation.336 M. respectively. The Redlich–Peterson model was also used to describe the adsorption phenomenon. The Redlich–Peterson equation has three parameters. qe the amount of solute adsorbed (mg/g) at equilibrium and qt the amount of solute on the surface of the adsorbent (mg/g) at any time t. k2. Adsorption isotherms (13) (16) where T is the temperature and C is the equilibrium concentration of the adsobate in solution. and Sips isotherms were generally used to describe observed adsorption phenomena of various metal ions on fly ash. and intraparticle diffusion model. and b were determined by curve fitting. through the following relationship: E ¼ 1=ð2bÞ 1=2 (17) Tempkin and Pyzhev considered the effects of some indirect adsorbate/adsorbate interactions on adsorption isotherms and suggested that because of these interactions the heat of adsorption of all the molecules in the layer would decrease linearly with coverage. The Langmuir isotherm applies to adsorption on completely homogenous surfaces with negligible interaction between adsorbed molecules. and K is an equilibrium constant that is related to the heat of adsorption by equation: q K ¼ Ko exp RT (11) where. including the Lagergren pseudo-first order kinetics. Parameter b ranges between 0 and 1. 1/n is sorption intensity. [65] investigated adsorption of Cr(III) on fly ash. Qm (mol/gm) is the DKR monolayer capacity. and other parameters have been defined as in Eq. which is related to the equilibrium concentration through the expression: 3 ¼ RTlnð1=CÞ 6. Vordonis et al. 6. resulted from high adsorbent concentration.and low-calcium contents and concluded that phosphate removal was primarily due to the precipitation of phosphate with Ca2þ ions in solution.57%) predominantly took place by precipitation mechanism. Linear property of ln Kc against 1/T was proved in a number of studies on adsorption of heavy metal by fly ash materials [79. For the amorphous and crystalline phases studied. The rate and efficiency of PO3 4 removal were found to increase in the order: fly ash.9836) and total Fe content (r ¼ 0. Interaction of inorganic orthophosphate at water/solid interface was investigated. It was concluded that P immobilization by fly ash was governed by Ca ingredient (especially CaO and CaSO4) and Fe ingredient (especially Fe2O3d). phosphate concentration. Another reason may be because of the particle interaction. the immobilization of phosphate in the fly ash is attributed to the formation of insoluble aluminum and iron phosphates at low to medium values of pH. Kc is equilibrium constant that is resulted from the ratio of equilibrium concentrations of metal ion on adsorbent and in the solution.51 to 42. at neutral pH levels for medium calcium fly ash. most metal adsorption increased with increased pH up to a certain value. fly ash emerges as a potential candidate to treat phosphate-laden effluents since aluminum. and fly ash dosage on phosphate removal was investigated. Acid modified fly ash was effective in the removal of phosphate from contaminated antibiotic wastewater. Blending OPC with fly ash or slag evidently resulted in diminished PO3 4 removal efficiency. Higher removal of phosphate occurred at alkaline conditions for high-calcium fly ash. [126] investigated the removal of phosphate on different fly ash. acidic fly ash for phosphate immobilization on the order of 100–75% for 50 and 100 mg P/L solutions. strongly adsorb or precipitate phosphates in many agricultural. but adsorption density. The regenerated fly ash was dried. such as.4. apparently mimicking the order of increasing percent CaO in the adsorbents. The adsorption capacity of fly ash depends on the surface activities. Chen et al. It was found that phosphate precipitation occurs immediately after introduction of coagulant. A positive DH0 suggests the endothermic nature of adsorption. [121] determined that uptake of orthophosphate by four calcium-rich (10–32%) Greek fly ash exceeded the amount predicted by monolayer coverage. Batabyal et al. Coal fly ash was paid great attention as a potential material for removal of phosphate. Phosphorous loading to surface and groundwater from concentrated agricultural activities. and boron also exists in waters and dangerous for human health. and after a short and intensive mixing because of very high total alkalinity of extract [114]. and DS0 is used to describe randomness at the solid–solution interface during adsorption. ionic size. The removal of phosphate ion from aqueous solution was compared with fly ash. The selection of a fly ash with a high phosphate sorption capacity is of utmost importance to obtain a sustained phosphate removal in the long term in practice. In a certain pH range. The influence of temperature.M. It is apparent that by increasing the adsorbent dose the adsorption efficiency increases. specific surface area available for solute surface interaction. chemical precipitation. The removal of phosphate by a medium calcium fly ash (with CaO content of 11.83%).98].1. while low-calcium fly ash immobilized little phosphate at all pH values. slag and ordinary Portland cement (OPC) and related cement blends [125]. cooled and used for further adsorption. Recently. industrial and environmental applications. suggesting either multilayer adsorption or precipitation. using suitable reagents. since it is easily available and cost effective [115–120]. Grubb et al. The adsorption rate and equilibrium time were same as the fresh fly ash particles. This behavior was explained by the reaction of phosphate with Ca and Fe related components. Ugurlu and Salman [116] found that a Turkish fly ash is an efficient adsorbent for removal of phosphate due to high concentration of calcite (33. 7. The Qm value showed a significantly positive correlation with total Ca content (r ¼ 0. and pig and poultry farms is causing water quality problems in rivers.8049). Because fly ash is enriched with oxides of aluminum. Fractionation of Phosphorus adsorbed by fly ash revealed that loosely bound Phosphorus fraction and/or Ca þ Mg-P fraction were the dominant form of immobilized phosphate. The decrease in adsorption density with increased adsorbent dose is mainly due to unsaturation of adsorption sites through adsorption reaction. but negative correlation with total Si and total Al content. Ahmaruzzaman / Progress in Energy and Combustion Science 36 (2010) 327–363 337 where Ks (L/g) and as (L/mg) are Sips isotherm constants and b is the exponent which lies between 1 and 0. such as phosphorous. and indicated that phosphate removal involved an adsorption and/or precipitation process. [124] carried out batch equilibration experiments using low calcium. some other inorganic contaminants. respectively. stability of bonds between heavy metals and fly ash. standard enthalpy change (DH0) and standard entropy change (DS0). Particle interaction may also desorb some of adsorbate that is only loosely and reversibly bound to carbon surface. diaries. Factors affecting adsorption of metal on fly ash 7. Removal of other inorganic components from wastewater Apart from heavy metals in wastewater. including soil fertilization. Thermodynamic parameters such as standard free energy change (DG0). A negative value of DG0 indicates the process to be feasible and spontaneous nature of adsorption. iron. Removal of phosphate The adsorption of heavy metals on fly ash is dependent on both the initial concentration of heavy metals and contact time. and increase of BET were main mechanisms of DG0 ln Kc ¼ RT ¼ DS0 R DH0 RT (22) where. The adsorption affinity of fly ash for heavy metal depends on the equilibrium between competitive adsorption from all the cations. such as aggregation. Adsorption. slag. DG0 or DS0 and DH0 are calculated from a plot of ln Kc versus 1/T. decreases. It is readily understood that the number of available adsorption sites increased with increased adsorption dose and resulted in increased removal efficiency. Tsitouridou and Georgiou [120] compared three fly ash with different calcium contents. It was reported that the initial concentration of heavy metal has a strong effect on the adsorption capacity of the fly ash. ion exchange and weak physical interactions between the surface of adsorbent and the metallic salts of phosphate [123]. and lakes. fluoride. calcium. The sorption maxima of phosphate (Qm) ranged from 5. are calculated using the following equation. which is accessible to the solute. and silica. OPC.55 mg/g. feed lots. and then decreases with further increase in pH. [113] regenerated the used saturated fly ash with 2% aqueous H2O2 solution. Cheung and Venkitachalam [122] investigated the removal of phosphate by fly ash with high. Such aggregation would lead to decrease in total surface area of adsorbent and an increase in diffusional path length [78]. the amount adsorbed per unit mass. Kuziemska first reported an investigation using water extract of brown coal fly ash as coagulant for precipitation of phosphate in 1980. iron and calcium are . Fly ash can be regenerated after the adsorption. The other important factor for the adsorption of heavy metal on fly ash is pH. respectively. With higher F concentrations in the feed solutions. glass etching and in ground water around aluminum smelters. molecules with strong functional groups align themselves vertically on the surface. and 2.2. display this type of behavior. hyperkalemia (excess blood potassium) which will affect spine. Chaturvedi et al. petroleum. Adsorption isotherms for phenol. Removal of boron Boron occurs naturally in environment. Fluoride concentration in industrial effluent is generally higher than in natural waters.4-dichlorophenol from water onto Texas Municipal Power Agency (TMPA) fly ash were determined [139]. including removal of colloidal organic and inorganic solids. having a very strong functional group as well as strong molecular interaction. chlorophenol. times. Solid phase phosphate compounds are separated from water by sedimentation or classical filtration. 8. F concentration in the effluent steadily decreased reaching 0 mg/L after 120–168 h. There is a need for defluoridation of industrial wastewaters. Boric acid and boron salts have extensive industrial use in the manufacture of glass and porcelain. indicating that adsorption becomes progressively . pesticide. At lowest F concentration. rubber and fertilizer manufacturing. 3-chlorophenol. electroplating. coal conversion. The chlorination of natural waters for disinfection produces chlorinated phenols.00 mg/L) were detected in Malbork drinking water. Adsorption of boron increased with increased pH. Crossflow microfiltration was effective in a number of processes. Removal of phosphate ions from water using fly ash in a crossflow microfiltration membrane unit was examined [129]. dental skeletal changes. [131] examined fly ash for removal of fluoride from water and wastewaters at different concentrations. and 2. which could not be explained by co-precipitation with CaCO3. Nemade et al. Removal of fluoride is favourable at low concentration. but higher levels can have an adverse effect on health. up to 12. Khanna and Malhotra [136] first examined the potential of fly ash for the removal of phenol. Fly ash has good adsorption potential for phenolic compounds. [134] examined the effect of ash particle size. and weakening of the bones. Wastewaters from phosphate fertilizer plants may contain up to 2% of fluoride. The problem of high fluoride concentration in ground water resource was an important health-related geo-environmental issue. Increased levels of fluoride can also be present in effluents from fluorine industry. Removal of phenolic compounds Phenols are important organic pollutants discharged into environment causing unpleasant taste. They reported kinetics and mechanism of phenol removal on fly ash and provided useful data in the design of phenol–fly ash adsorption systems. glass and ceramic production. respectively. These methods were divided into two groups: (a) precipitation methods based on addition of chemicals to water and (b) adsorption methods in which fluoride is removed by adsorption or ion exchange reactions on some suitable substrate. They explained that the three phenolic compounds. and upper regions of Ghana. and odour of drinking water. because of excessive amounts of fluoride may cause adverse health effects to humans and animals. and macromolecules [127. 20. cosmetics and photographic chemicals. The Thomas and Yoon–Nelson models were applied to experimental data to predict breakthrough curves. and it is commonly found in oceans. In the Gdansk region. Retention of fluoride ion in dynamic experiments on columns packed with fly ash was studied in aqueous solutions [133]. cerebral impairment. The presence of excessive fluorides in drinking water is a matter of serious concern. and cresol. and 22 mg/g for phenol. Fly ash has a good adsorption potential for phenolic compounds. It is present as boric acid and borate ions in aqueous solution. The Freundlich isotherm was more suitable for all the systems investigated. Adsorption of boron from aqueous solution using fly ash was investigated in batch and column reactors [135]. There are several methods reported for the removal of pollutants from effluents. ranging from tens to thousands of mg/L. Excess fluoride consumption also leads to cancer. Coal fly ash is an effective adsorbent for F ions.338 M.4-dichlorophenol. cerbrovascular effects.87 m2/g. pH. High fluoride containing wastewater is generated by coal power plants. semiconductor manufacturing. The affinity of phenolic compounds for fly ash is above the expected amount corresponding to a monolayer coverage considering that the surface area of fly ash is only 1. carpets. The addition of fly ash to water produces insoluble or low solubility salt when combined with phosphate. where 23% of wells have fluoride concentrations above WHO recommended maximum guideline limit of 1. in wire drawing. [132] carried out batch adsorption studies to determine removal efficiency of fluoride by fly ash.1. osteoporosis. and other physical ailments. and their mixtures from aqueous solutions on activated carbon and fly ash were compared [137].3. neurological. However. Very few investigations were reported on boron adsorption using fly ash. The effects of contact time and initial solute concentration have been studied and isotherm parameters were evaluated. making the next adsorption layer energetically and statistically more favorable. and petrochemicals industries. India. The fluoride toxicity indicates that it cause weight loss. and to determine characteristics parameters of the column useful for process design. capable of regeneration and reuse [130].128]. polymeric resin.5 mg/L. high fluoride levels (1. Table 3 presents a summary of adsorption capacity of various organic compounds on fly ash. Adsorption of phenol. production of leather. and cations from aqueous streams with the aid of surfactants. This was attributed to a ligand exchange mechanism. and various anions. Major sources of phenol pollution in aquatic environment are wastewaters from paint. where nearly 3 million people are reported to consume excess fluoride containing water. these adsorbed molecules can interact with other molecules. indicators of carcinogenesis. temperatures and pH of the solution. The isotherms examined were unfavourable (BET Type III) or cooperative (Curve S). Ahmaruzzaman / Progress in Energy and Combustion Science 36 (2010) 327–363 removal of phosphate with modified fly ash. and damage of soft tissues. 7. Examples include the state of Rajasthan. Hollis et al. Removal of fluoride Fluoride in water is essential for protection against dental caries. Several investigations were reported for the removal of fluoride from waters by using fly ash. hypocalcemia (low blood calcium). for the highest water phase concentrations. and Ca(OH)2 on dissolution and adsorption of boron by fly ash in aqueous media.90–3. 7. F level in the effluent initially increased and then gradually decreased down to 0 mg/L after 120 h. Membrane process is being used for various water and wastewater treatment applications. Removal of organic compounds from wastewater 8. The fly ash adsorbed 67. and weatherproofing wood. for fireproofing fabrics. high temperature and acidic pH. But some fly ash particles may remain in the water and cause turbidity. especially at high concentrations in water. there can also be formidable contributions from industries. Various methods have been used to remove fluoride from wastewaters. Removal of phenol depends markedly on temperature and pH value of treatment solution [138]. moreover. Besides natural geological enrichment of fluoride in ground waters. A small amount of born was adsorbed by fly ash at pH 7. on fly ash. Batch adsorption experiments were conducted to estimate the potential of fly ash (FA) for removal of phenols from aqueous solution [150. Fly ash was successfully used to recover phenol from industrial wastewater. The effect of nitrate ion and EDTA on adsorption of phenol was insignificant. phenol (hydroxybenzene). Substituted phenol with hindered group is less adsorbed than phenol (m-nitrophenol > o-nitrophenol > phenol > m-cresol > o-cresol).6%. [147] utilized fly ash for removal of 2-chlorophenol (2CP) and 2. fly ash and bentonite in removing phenol from wastewater was also examined [148]. electron withdrawal or deactivation of benzene ring favors formation of electron-donor–acceptor complexes between these rings and basic groups on the surface of fly ash.54–1.8 5.1%. Chloride ion has considerable negative effects on removal by BA. The effectiveness of less expensive adsorbents such as peat. m-hydroxyphenol (1. resulting in vertical alignment of the molecule on the surface.5 52. Chlorophenols in wastewater were also removed efficiently through a fly ash column. The ultimate capacity of the adsorbent is considerably less than that predicted from summing the single-component data. Adsorption of chlorophenol is not influenced by matrix in wastewater.7) 103 (6.4 Dimethyl phenol DDD DDE Lindane Malathion Carbofuran TCB HeCB [147] [142] [139] [141] [151] [143] [142] [151] [143] [142] [143] [146] [134] [113] [160] [161] [162] [164] easier as more solutes are taken up. o-hydroxyphenol (1. by lagooning mixture of fly ash and wastewater. 339 Sarkar et al.7) 103 (2.M.2-dihydroxybenzene).4-dimethyl phenol by adsorption from aqueous solutions [113]. viz. m-cresol (m-Cr). respectively. Therefore.3-dihydroxybenzene).6 118. The estimation of diffusion coefficients indicated that film diffusion control adsorption of phenol.4-dichlorophenol and tetrachlorocatechol [152.153].07 105.141].15 134.7 20 118. Activation parameter data for ultimate adsorption and pore diffusion are also evaluated. Rice husk ash (RHA) obtained from a rice mill in Kenya was used for removal of some phenolic compounds in water [155]. and 4-nitrophenol (1-hydroxy-4-nitrobenzene).66 0.4–2. The effect of molecular weight and molecular configuration on adsorption of phenol (Ph). Adsorption of phenolic compounds on a mixture of bottom and fly ash was reported [142].4-dichlorophenol (2. The process was complex consisting of both surface adsorption and pore diffusion.3 85.35 0. The breakthrough time was inversely proportional to flow rates.5–7. Polar substituted phenol.5 1. More adsorption takes place with fly ash of higher carbon content and larger specific surface area. rice husk fly ash (RHFA) and activated carbon (AC) were also investigated for adsorption of 2. Activated carbon (AC).7 22 1.8–1. and 1.53 104.4 0. this was attributed to increased competition for adsorption sites. bagasse ash (BA) and wood charcoal (WC) were also used as adsorbents for removal of phenol from water [157]. The rate of adsorption is controlled by both diffusional and kinetic resistances at higher temperature. Adsorbent prepared from fly ash was successfully used to remove cresol from an aqueous solution in a batch reactor [146]. The removal mechanism of phenol is explained due to chemical coagulation with metallic oxides. The data indicate that external transport mainly governs rate-limiting process. additional adsorption is motivated and consequently strengthened by the interaction between the adsorbed molecules.9 7.06 0.9 mg/g for fly ash and 108.65 0. Intraparticle model shows the presence of two separate stages in adsorption process.63 106 mol/g were determined for phenol. respectively. Kao et al. Removal of pesticides Among various organic and inorganic water pollutants. The uptake increases when larger quantities of adsorbent are used. namely..15 [139] [143] [148] [142] [147] [141] Ortho-chloro phenol 2. Phenols have a strong hydroxyl functional group which interacts with the adsorbent surfaces. Adsorption capacities of 1. 41. The presence of an anionic detergent Manoxol-IB reduces uptake of phenol and p-nitrophenol.47–0. The overall adsorption process is controlled by intraparticle diffusion of phenol. raw sepiolite and heat-activated sepiolite as adsorbent [158]. p-cresol (p-Cr). 8. The efficiency of adsorption decreases with increased adsorption temperature for both fly ash and untreated sepiolite. This phenomenon is known to contribute significantly to the cooperative nature of adsorption and hence an S type curve. Organic compounds Adsorbent Capacity (mg/g) References Phenol FA Sugar fly ash FA-C Wood FA Coal-FA FA-C Fly ash FA Coal FA FA FA-C Fly ash Wood FA FA FA Sugar fly ash Wood FA FA Bagasse fly ash Coal FA Wood FA Wood FA Fly ash Sugar FA Sugar FA Bagasse FA Bagasse FA FA FA FA 67 0.26 5.2.80–6.80–9.4-DCP). The potential of fly ash as a substitute for activated carbon for the removal of phenolic compounds from wastewater was examined [140.0 mg/g for granular activated carbon. The potential of rice husk and rice husk ash for phenol adsorption from aqueous solution was examined [154].5–6. having less steric hindrance is better adsorbed than others.4 34.0–2. Heat-activated sepiolite is more effective than raw sepiolite and fly ash. Regeneration of used fly ash with H2O2 indicates that fly ash may be a useful cheap industrial adsorbent for wastewater treatment. The high negative value of change in Gibbs free energy (DG0) indicates feasible and spontaneous adsorption of phenol on BFA.151].5% phenol.1) 103 1. This order is related to electron-withdrawing properties of substituents of phenolic compound. 8. Bagasse fly ash was converted into a low-cost adsorbent and used for removal of phenolic compounds [143–145]. resorcinol and 2-chlorophenol. pesticides are very dangerous and harmful because of their toxic and . rate of adsorption is dominated by diffusion effect. [156] studied the adsorption of phenol on carbon rich bagasse fly ash (BFA) and activated carboncommercial grade (ACC) and laboratory grade (ACL). Phenolic compounds from paper mill industry wastewaters were removed by using fly ash. [149] investigated the adsorption of some priority organic pollutants.5) 103 (2. fly ash and bentonite were found to adsorb 46. Peat.4-Dichloro phenol 3-Chloro phenol Para-chloro phenol 2-Nitro phenol 3-Nitro phenol 4-Nitro phenol Para-nitro phenol Cresol m-Cresol p-Cresol 2. The maximum phenol loading capacity of each adsorbent was 27.68 8. 2-nitrophenol (2-NP) and 4-nitrophenol (4-NP) from aqueous solution was investigated. Rice husk ash is very effective than rice husk for phenol removal.7 98. Coal fly ash was used successfully to remove 2. phenol was reduced from 4500 mg/L to 280 mg/L [159].5–1.44 6.0 98.6 143.52–8. and 42. Both diffusional and kinetic resistances affect the rate of adsorption and their relative effects vary with operating temperatures.39 (7. Moreover. external diffusion and pore diffusion. Bagasse fly ash (BFA). Srivastava et al.76–1. Ahmaruzzaman / Progress in Energy and Combustion Science 36 (2010) 327–363 Table 3 Comparison of organic pollutant adsorption on fly ash. whereas at low temperature.4–96. A significant correlation was observed between rate of adsorption and inverse of the square of particle diameter.3. Remazol Red 133 (RR) and Rifacion Yellow HED (RY) from aqueous solutions on fly ash (FA) were studied in a batch mode operation [177]. . with decreased initial pond effluent organic concentrations and sizes of ash.1-dichloroethane] and DDE [2. Ahmaruzzaman / Progress in Energy and Combustion Science 36 (2010) 327–363 carcinogenic nature. Potential of fly ash as adsorbent for removal of Chrysoidine R from aqueous solution was reported by Matheswaran and Karunanithi [174]. initial pond effluent organic concentrations. a fixed-bed column was designed. Removal of other organic compounds Banerjee et al. The adsorption of reactive dyes (Remazol Red. aldehydes and ketones. adsorption is controlled by film diffusion. Adsorption of o-xylene by fly ash is an exothermic process and spontaneous at the temperature investigated. The FTIR suggested that dye on fly ash is probably indicating fly ash/dye complexation.6 and 49. Removal of dyes from wastewater Dyes and pigments are discharged into wastewaters from various industrial sources. Reactive Black 5 onto high-lime fly ash was studied to characterize of the surface complexation reaction. An azo dye. Bhargava et al. Batch adsorption studies were carried out for sorption of C.2-bis(4-chlorophenyl)1. Uptake rate of o-xylene increases significantly with increased initial concentration. 8. concentrations. respectively. Thiazine dyes Thiazine dyes are suitable for the study of photo-sensitized reactions in micellar media.acetic acid. it is controlled by particle diffusion mechanisms. External mass transfer and intraparticle diffusion had rate limiting affects on the removal process. The removal was achieved up to 97–98% in column experiments at a flow rate of 0. and necessary parameters were calculated by applying a mass transfer kinetic approach. To assess the practical utility of adsorbents. Adsorption of carbofuran on fly ash was studied by Kumari and Saxena [162]. and pH [172]. Adsorption of TCB and HeCB was decreased when interfering ions and other PCB congeners were present. Acid Orange 7 [p-(2hydroxy-1 naphthylazo) benzene sulfonic acid] was removed by adsorption onto bottom ash [175]. mainly from dye manufacturing and textile finishing industries. fly ash is used for an efficient removal of PCBs from aqueous solutions. Adsorption of the CR on BFA was most favourable in comparison to activated carbons.1. The adsorption kinetics of C. Bagasse fly ash was also examined for removal of lindane and malathion from wastewater [161]. while at higher concentrations. A series of experiments were carried out in a batch adsorption technique to obtain the effect of process variables on adsorption. 9. beta-naphthoxyacetic acid. Adsorption kinetics of PCBs on fly ash was conducted in controlled batch systems [164]. Cu.2-bis(4-chlorophenyl)-1. 63. methylene blue.1-dichloroethene] pesticides from wastewater [160]. indole-3. Fe and Ni [163].340 M. The uptake rate of TCB and HeCB increases with increased initial concentration and gradually tends to a constant value. TCB and HeCB are removed up to 97%. Factors affecting organic pollutant removals. Various researchers have examined the potential of fly ash for removal of azo dyes from wastewater. Activation energies for adsorption process ranged between 3. Adsorption kinetic and equilibrium studies of Remazol Brillant Blue (RB).2. aldehydes. [165] investigated the adsorption of o-xylene on fly ash. Adsorption of dye on fly ash was described using pseudo-first order and pseudo-second order kinetics. from aqueous solution [179]. Reactive Black 5 onto high-lime fly ash [176]. especially if the adsorbent is inexpensive and does not require an additional pre-treatment before its application. Remazol Blue and Rifacion Yellow) from aqueous solutions using fly ash as an adsorbent was examined [178].I. Percent reductions of aromatic compounds were much higher compared to other functional groups such as alcohols. Cd. oxalic acid and trichloroacetic acid from water were 75%. The organic removal efficiency increased with increased ash concentrations. Overall. betanaphthaleneacetic acid. Table 4 summarizes the adsorption capacity of various dyes onto fly ash. Bagasse fly ash was converted into an effective adsorbent and used for removal of DDD [2. Adsorption of o-xylene onto fly ash was controlled by diffusion process. 95. 100%. The rate at which TCB and HeCB are adsorbed onto fly ash showed a diffusion limitation.27% carbon. 74% removal of ABS was obtained with a 2-h contact time [168]. Bagasse fly ash (BFA) was also utilized for the adsorption of Congo red (CR) from aqueous solution [173]. This was attributed to relatively simple macropore structure of FA particles.25%. temperatures. Among them. Batch shaking was conducted to determine the adsorption potential of fly and volcanic ashes in removing organic pollutants from oxidation pond effluents [171]. Fly ash has been employed as adsorbents for the removal of a typical basic dye. 9. Surface morphology of fly ash and dye loaded fly ash were obtained with SEM. Fly ash was also used to remove TNT in both batch and column systems. and gradually approaches a plateau. [167] examined removal of a detergent in a fixed-bed continuous flow fly ash column and developed a relationship for the design of such systems.5 mL/min. which form bridges between two or more aromatic rings. The adsorbent was characterized using several methods such as SEM. Activation energies for the adsorption process ranged between 5. such as concentrations and sizes of fly and volcanic ashes. The TOC (total organic carbon) removal efficiency varied from 30 to 58%. The degree of adsorption of carbofuran was determined in accordance with the partial molar free energies and Kd values. Experiments were also performed for recovery of loaded dye through chemical regeneration of spent columns. washed and unwashed conditions of fly and volcanic ashes.I. because of their low ionization potential caused by the presence of two hetero-atoms. At lower concentrations. Fly ash was also used as adsorbent for the removal of alcohols. Azo dyes The Azo dyes are largest and most important group of dyes. Using 1000 mg/L of fly ash containing 23. The adsorption of Congo red from solution was carried out using calcium-rich fly ash with different contact times.71% and 78. were investigated. adsorption process provides an attractive alternative for the treatment of wastewaters.26%. Batch studies were carried out to investigate the removal of organic acids by adsorption on fly ash impregnated with hydroxides of Al. 9. [169] showed that adsorption of oxalic acid from aqueous solution by fly ash has two linear components each following Langmuir isotherm.3 kcal/mol. in column systems 90% removal of TNT was reported [166]. Removal of reactive dyes from aqueous solutions using FA was well described by external mass transfer and intraparticle diffusion models. 85. Jain et al.1 and 4. XRD pattern of fly ash consisted of mainly quartz.63%.1 kJ/mol. There are various methods available for the treatment of dyes from wastewater. XRD and FTIR. The percentage removals of cinnamic acid. The DDD and DDE are removed up to 93%. ketones and aromatics [170]. They are characterized by the presence of one or more azo groups. The residual carbon content played a significant role in adsorption process. namely nitrogen and sulphur. Immobilization of organic pollutants is feasible by adsorbing contaminants onto fly ash. mullite with some magnetite and calcite. 0 106 (16–40) 106 1. The equilibrium saturation adsorption capacities of fly ash for TB decreased in presence of CPC as a result of competitive adsorption for same sites between same Temperature ( C) Adsorption isotherm 25 22 30 30 30 30 30 Langmuir Langmuir Redlich–Peterson Redlich–Peterson Langmuir and Freundlich Langmuir and Freundlich Langmuir and Freundlich Redlich–Peterson Redlich–Peterson Langmuir Langmuir Kinetic model References [202] [205] [186] [182] [186] Pseudo-second order 25 25 [189] 25 Freundlich Langmuir Langmuir Lagergren first order 25 22 25 25 Freundlich Langmuir Lagergren first order 22 22 22 22 – – – Langmuir Langmuir Langmuir Langmuir Freundlich Freundlich Freundlich – 20 Freundlich Freundlich [179] [190] [204] [186] [177] [204] [205] [189] [205] [203] Pseudo-second order [172] [173] [197] [205] [198] charged dye and surfactant molecules. in acidified situation. be removed by using a two-stage fly ash sorption process.20 105 2.46 7. The adsorption of toluidine blue (TB) onto fly ash was studied from aqueous solution. in presence of cationic surfactant cetyl pyridinium chloride (CPC) and anionic surfactant sodium dodecyl sulfate (SDS) [183]. in both an untreated and an acidified form. Ahmaruzzaman / Progress in Energy and Combustion Science 36 (2010) 327–363 341 Table 4 Comparison of dye adsorption on fly ash. Fly ash samples modified by NaOH solution and sonochemical treatment were examined for a basic dye (methylene blue) adsorption in aqueous solution [182]. sorption on fly ash surface by silica. An increase in specific surface area and dye-adsorption capacity was observed after acid treatment.4 105 2. Two-step adsorption isotherms are observed for TB adsorption in aqueous solution. calcium precipitation of tannins and humics. The adsorption capacity of HCl treated fly ash varies. Many of these materials can.36 104 1.70 105 4.4 10 1. The fly ash treated by H2SO4 was used as a low-cost adsorbent for the removal of a typical dye. from aqueous solution [185]. whereas acid treatment by HNO3 induces a different effect on fly ash. Fly ash.13 105 1. and therefore global adsolubilization decreases. from aqueous solution [181].76 105 1.2 105 6. The apparent predominant mechanism varies with pH and chemical characteristics of the ash.67 104 3. Chemical treatment using HCl will increase adsorption capacity. Nitric acid treatment results in an increase in the adsorption capacity of fly ash.05 104 4. alumina. methylene blue. however.4 105 mol/g). Microwave treatment is a fast and efficient method while producing sample with highest adsorption capacity.0 106 1.15 105 8.5 107 1.0 106 8. TB is distributed between free and adsorbed aggregates.34 106 1. Adsorption capacity of fly ash is dominantly contributed by porous unburned carbon in fly ash.4 105 2 106 1. An adsorption isotherm of SDS and CPC in aqueous solution was constructed for interpreting adsorption results of TB in presence of surfactants. There is a significant linear correlation between carbon content and . Above critical micelle concentration free micelles are formed.4 105 2.6 106 2.15 105 Heat treatment and chemical treatment have also been applied to the as-received fly ash and red mud samples. Heat treatment reduces adsorption capacity.47 105 1. The effect of different methods for fly ash treatment using conventional chemical. coagulation of coloured colloids in effluent dissolved from fly ash.89 105 1. Fly ash and treated fly ash by physical and chemical methods was employed as adsorbents for the removal of a typical basic dye.35 105 1. methylene blue. Sonochemical treatment of fly ash can significantly increase adsorption capacity depending on the concentration of NaOH and treatment time.15 105 2.4 105 mol/g and that heat treatment reduces adsorption capacity but acid treatment by HNO3 results in an increase in adsorption capacity of fly ash (2.0 104 9.2 104 2 105 >2 105 >1. Dye Methylene blue Crystal violet Rosaniline hydrochloride Rhodamine B Egacid orange II Egacid red G Egacid yellow G Midlon black VL Acid blue 29 Acid blue 9 Acid red 91 Acid red 91 Acid red 91 Congo red Malachite green Egacid orange II Orange-G Fly ash type Coal FA FA-F FA-F FA-HNO3 FA FA-NaOH FA-NaOH-sono FA FA-HNO3 FA Carbon –enriched FA FA Colombian FA Thailand FA Fly ash Fly ash Coal FA Carbon-free FA Carbon –enriched FA Fly ash Coal FA FA-F Colombian FA Thailand FA Fly ash (CFA) FA-F FA-F FA-F FA-F FA FA FA Fly ash FA FA-C Baggase fly ash Baggase fly ash Fly ash (CFA) Bagasse fly ash Adsorption capacity (mol/g) 5 14.20 105 3. These mechanisms include carbon adsorption. and/or iron oxide and.3 105 3. Raw fly ash showed adsorption capacity at 1.26 106 4. sonochemical and microwave method on methylene blue dye adsorption in aqueous solution was investigated [180].40 104 5.43 106 2.0 106 2. were examined with respect to their ability to remove colour and organic materials [184].01 105 9. rather than fly ash itself [186].M. The adsorption of cationic dye at low SDS concentration is enhanced by adsolubilization phenomenon because of favorable interaction with negatively charged adsorbed micelles.25 106 5. Further investigation show that unburned carbon exhibits much high adsorption capacity than mineral parts of fly ash [187]. [191. The percentage of dye removal was higher at high adsorbent concentrations. but in which some of the hydrogen atoms are replaced with aryl rings.5. they may also legitimately be called phenylmethane dyes. 9. The percentages of removal of alizarin yellow and fast green were 87. Orange-G (OG). The pronounced removal of chrome dye in acidic range may be due to the association of dye anions with positively charged surface of adsorbent. All above reports demonstrated that fly ash could be an effective adsorbent for removal of various dyes from wastewater. [195] investigated the potential of bottom ash for removal of alizarin yellow and fast green from wastewater. In the RB adsorption. pore volume and pore size exhibiting its potential to be used as an adsorbent for the removal of AO. Bottom ash was examined for the removal of toxic textile dye. The presence of oppositely charged surfactants exhibited a pronounced effect on dye sorption – low concentrations of surfactant enhanced sorption. Since a synonym for aryl is phenyl. [199]. This class of dyes is generally divided into two categories: diarylemethane and triarylmethane. Adsorption of BG on bagasse fly ash is favorably influenced by an increase in operation temperature. and 97. Bagasse fly ash was also used for the removal of methylene blue [190].342 M. Adsorption increased with dye concentration and that the maximum removal was achieved at pH 8. These adsorbents possess several advantages . Amorphous aluminosilicate geopolymers is formed and assessed as potential adsorbents for removal of crystal violet. without any pre-treatment showed high surface area. respectively. metals and organic compounds from wastewater [208–239]. and benzyldimethyltetradecylammonium (TEA. The adsorption behavior was strongly depended on the characteristics of the individual fly ash. Adsorbents from coal fly ash were prepared by a solid-state fusion method using NaOH [201]. Coal fly ash was used as a heterogeneous catalyst in peroxidative decolorization of aqueous solution of several reactive drimarene dyes using hydrogen peroxide [206]. Lime content in fly ash influenced the dye adsorption to a significant degree – better adsorption was observed at lower particle sizes because of increased external surface area available for adsorption. Crini [240] has recently reviewed the low-cost non-conventional adsorbents utilized for removal of dyes from wastewater. The potential of coal fly ash for the removal of Rhodamine B (RB) from aqueous solution has been studied [189].0. BFA. He demonstrated that non-conventional low-cost adsorbents have potential as readily available.195].192] investigated the ability of fly ash and mixture of fly ash and coal to remove Omega Chrome Red ME from aqueous solutions. Bagasse fly ash was also utilized for the removal of rhodamine B [190].5. the maximum adsorption was observed between pH 2. Fly ash derived geopolymeric adsorbents show higher adsorption capacity for crystal violet than methylene blue. Adsorption of various dyes. Gupta et al. It is also evident from the literature that natural materials. The efficacy of surface modification of fly ash by quaternary ammonium cations in the removal of dyes from aqueous solution is demonstrated [207]. waste materials from industry and agriculture and bio-adsorbents are an interesting alternative to replace activated carbon for the adsorption of dyes. inexpensive and effective adsorbents. 9. A fixed-bed column was designed and necessary parameters were calculated by applying mass transfer kinetic approach. acetone).5. and BDTDA). The removal of each dye was inversely proportional to the size of fly ash particle.8 and 4. Bagasse fly ash was also used for the adsorption of brilliant green (BG) [200]. The utilization of coal fly ash for the removal of dye (Victoria Blue) from aqueous solution was first reported by Khare et al. The presence of anionic surfactant will decrease methylene blue adsorption. The potential of fly ash for removal of crystal violet dyes was reported [180]. The synthesized materials exhibit much higher adsorption capacity than fly ash itself and natural zeolite. The presence of anionic surfactant does not affect the uptake of rhodamine B significantly. Arylmethane dyes Arylmethane dyes are so called because they are derived from methane. The percentage of dye removal was higher at high adsorbent concentrations. Other dyes Ramakrishna and Viraraghavan [202–204] investigated the potential of fly ash for removal of dyes from wastewater. namely. The adsorption was affected by structure and size of quaternary ammonium cations and dyes. Ahmaruzzaman / Progress in Energy and Combustion Science 36 (2010) 327–363 adsorption capacity. The adsorption process was found to be controlled by both film and pore diffusion with film diffusion at earlier stages followed by pore diffusion at later stages. Pseudo-second order kinetic model would be better in describing kinetics of dye adsorption than first order kinetics [188]. Adsorption of MV on BFA (with a more negative Gibbs free energy value) is more favored among the dyes studied. from aqueous solution. Recovery of Brilliant Blue FCF was made by eluting dilute NaOH of pH 11 through each column. The dye adsorption decreased in presence of organic solvents (methanol. sonochemical and microwave method on dye adsorption in aqueous solution was investigated. Inorganic salts exhibited only a minor effect on dye sorption.4. The effect of different methods for fly ash treatment using conventional chemical. Gupta et al. Chemical treatment with HCl will increase the adsorption capacity. Adsorption of dyes was considerably enhanced by surface modification.198]. The use of coal fly ash for removal of dyes. and Methyl Violet (MV) was investigated extensively from aqueous solution by using bagasse fly ash (BFA) [197. Adsorption capacity of synthesized adsorbents depend on preparation conditions such as NaOH: fly ash ratio and fusion temperature with optimal conditions being at 1. The adsorption behavior strongly depended on the characteristics of individual fly ashes. whereas high concentrations solubilised dyes and kept them in solution. malachite green [193].3. HDTMA. Rhodamine B is strongly adsorbed at pH 2.2:1 weight ratio of Na: fly ash at 250– 350 C. sonochemical and microwave method on Rhodamine B dye adsorption in aqueous solution was investigated [180]. hexadecyltrimethylammonium.The adsorption of Auramine-O (AO) dye on bagasse fly ash (BFA) and activated carbon-commercial grade (ACC) and laboratory grade (ACL) was investigated [196]. Xanthene dyes Xanthene dyes are derived from xanthene. Plausible mechanism of on-going adsorption process and thermodynamic parameters involved were obtained by carrying out kinetic measurements. 9. Bottom ash was also utilized as adsorbent for removal of Brilliant Blue FCF and methyl violet [194. methylene blue (MB) from aqueous solution was investigated [189]. The effect of different methods for fly ash treatment using conventional chemical. A series of organo-fly ash materials were synthesized by treating fly ash with quaternary ammonium cations such as tetraethylammonium. malachite green. The adsorption of MB increased slightly and linearly with increase in solution pH. Brown coal fly ash was also examined as low-cost adsorbents for removal of synthetic dyes from waters [205]. 91 6. (iii) The competitive adsorption of organic compounds on fly ash was reported in few cases. silica beads. Pb.43 20. Cs and Nb possess a smaller volatilized fraction during coal combustion [245]. (iv) There is a lack of data concerning the reproducibility of the adsorption properties and the equilibrium data. such as high capacity and rate of adsorption. dyes and metals on various other adsorbents. As. Mo. SiO2. Elements.24 5. charred sawdust. Be. Leachate waters have markedly different compositions. Zn. The elements present were divided into two groups based on their concentration dependence of particle size. Organic compounds Adsorbent Capacity (mg/g) References Phenol Coal Residual coal Residual coal treated with H3PO4 Rice husk Coke breeze Rice husk Rice husk char Petroleum coke Lignite Neutralized red mud Sewage sludge 13. Se. F. such as. Ag and Zn are either not volatilized or may show minor trends related to geochemistry of mineral matter. high selectivity for different concentrations and also rapid kinetics. Ga. The industrial effluents were found to contain several pollutants simultaneously. The surface layer of fly ash particles. Tb. Cd. Sb. CO3 with aqueous extracts of ash saturated with Ca(OH)2. commonly known as the adsorption isotherms. Mg. However. There are several issues and drawbacks concerned on the adsorption of organic compounds that should be addressed: (i) The applicability of fly ash as low-cost adsorbents for wastewater treatment depends strongly on its origin. Table 5 Comparison of adsorption on phenols. residual coal treated with H3PO4. Total dissolved solid concentrations may vary from hundreds to tens of thousands of milligram/liter. cyclodextrin.241. Sm. Some promising results could be found in the case of clays. Se.65 5. Hg and S are usually volatile to a significant extent in combustion process. flue gas process conditions design of combustion systems. are formed over a wide range of temperatures in furnace.01 10. A small sample can show marked differences in leachate water chemistry.249] showed that the principal cations in water extracts are calcium and sodium.0 [215] Waste news paper Coal Sewage sludge Rice husk Straw Date pits Hazelnut shell Coir pith Banana peel Orange peel 390 250 114. It is evident that fly ash has a great potential in the environmental applications. B. Ba. Cu. Fly ash is an interesting alternative to replace activated carbon or zeolites for adsorption in the water pollution treatment. Studies have shown that only about 1–3% fly ash material is soluble in water with lignite fly ash of higher proportion of water soluble constituents [247]. Ni. Mo. dye. 10. depending on the surface of fly ash.23 45.83 19.251]. and metal on other adsorbents in order to compare with fly ash. Analysis of water extracts [248. adsorption capacity. Therefore.40 12. B. (ii) The effectiveness of adsorption process depends on the properties of the adsorbent and adsorbate. K. Nd. The development of the adsorption process requires further investigation in the direction of testing fly ash adsorbents with the real industrial effluents. Na. The leaching of major elements from CFA was extensively reviewed [11].6 11.8 4. All these phases are . Se. Further work in this area is needed. This creates a problem of secondary environmental pollution. The volatility of trace elements increased from larger to smaller particle size and establishes an inverse relationship of volatility and particle size [246].82 120.0 4. bentonite. Sn. the charge on the surface of fly ash particle and formation of diffuse double layer plays a significant role in leaching. and sludge materials. However.53 [226] [227] [225] [233] [234] [235] [236] [228] [237] [224] [225] [238] [63] Dye (Basic blue 9) Metal (Zn2þ) [208] [209] [210] [218] [217] [219] [216] 343 existence of competing organic or inorganic compounds in solution. Ni. more research should be conducted in this area. such as. residual coal. The mineral and glass phases constitute fly ash material. Despite the number of published laboratory data. and Al2O3 content in the fly ash generally varies with regions and thus. petroleum coke. V and Zn. Y. Cr. The design and efficient operation of the adsorption processes also requires equilibrium adsorption data for use in the kinetic and mass transfer models. Leaching of fly ash in water system Utilization of fly ash in water involves the potential leaching of some elements into water. little attention has been paid to the adsorption of pollutants from the mixtures [244]. As.45 142. Fe. Br. Rb. coal. Eu.242]. As.3 95 73 12 11 168 35. peat and chitosan-based materials [229. Zr. Be. and whether lime or lime stone injection processes were implemented for desulfurization. Cr.508 0. The alkalinity and acidity controlled extractability of elements. The volatility is directly proportional to particle size. Yb. Some promising results could be found in the case of fungal biomass. Se and V [250. Zn. depending on reaction time and water/solid ratio in batch equilibration’s or with column length. F. ionic strength. The volatility for these elements is inversely proportional to particle size.3 8. Cd. Py. Mo. starch. probably of microns in thickness.57 15. contact time and speed of rotation etc. Table 5 reported the adsorption capacities of phenol. fly ash adsorbent has not been applied at an industrial scale.172 4. Co. The elements Mn. La. V. Ahmaruzzaman / Progress in Energy and Combustion Science 36 (2010) 327–363 that make them excellent materials for environmental purposes.508 7. Ca. Therefore. It also depends on the environmental conditions and variables used for the adsorption process such as pH. and flow rate in a dynamic leaching test.2 18. Ahmaruzzaman [243] recently reviewed the adsorption of phenolic compounds on low-cost adsorbents. Ce. Sr.59 17. Ta. whereas anions are dominated by OH. Co. The percentage of unburned carbon. initial adsorbent concentration.M. Aqueous extracts of an acidic fly ash contained concentrations of Cd. Na.6 [222] [220] [223] [221] Blast furnace slag Lignin Lignin Acid washed-tea industry waste Tea industry waste Powered waste sludge Sugar beet pulp Lignin Solid residue of olive mill products Red mud Blast furnace slag Coffee Husk Clarified sludge 103. Th. The elements Si. Ln. Mn. temperature.82 17.94 19. contains a significant amount of readily leachable material deposited during cooling after combustion. there is scarce data available for the adsorption of organic compounds in presence of metals and other contaminants. Cu.127 94. As. These models play an important role in predictive modeling for analysis and design of adsorption systems. sulfate. or benzene. In the neutralization reactions. pH. concentrated nitric acid under microwave conditions. mullite and quartz could also account for their non-detectability. oxides and chlorides formed at high temperatures in coal-fired power generating stations [11. However. Polat et al. ash particles are surrounded by a bitumen or cement layer preventing water seepage. it is suggested that following measures/steps should be taken before fly ash is used as adsorbent for wastewater treatment: (1) leaching behaviour test for water system.344 M. Unlike equilibration of fly ash with demineralized water. It is expected that fly ash will add alkalinity and increase the pH on contacting acid mine drainage (AMD). (4) destruction of persistent organic pollutants. [262] compared fly ash. limestone and fly ash as pre-treatment agents for acid mine drainage. They dissolve and then precipitate as stable and less soluble secondary phases. Hence.263]. Trace metal concentration in the leachate depends on fly ash weight/solution. nitrates. when well compacted. compared with the lower base courses. Dilution by the major phases of fly ash such as glass. temperature. thinner. Therefore. Due to the low solubility. When fly ash contacts water these phases will dissolve completely. rapid leaching of most of the trace metals (except Cu). Al.269] established that conducting leaching tests on a particular waste material at least at two different liquid/solid (L/S) ratios can differentiate between these two classes of species. There are traces of polycyclic aromatic hydrocarbons present in the coal fly ash. such minerals are not available or actual in the FA residue for any future mineralogical study.270] and hence cannot be detected by XRD. all trace elements lie within acceptable limits [255]. Determination of whether the concentration of an element in fly ash leachate is controlled by mineral solubility is a challenge. typically up to 25 mg/kg. A simple increase in concentration when FA: AMD (Fly ash: AMD) ratio is doubled maintained for the duration of the experiment may signify nonexistence of solubility control. Secondary hydrous alumino silicate products are very insoluble [252] and build up on rinds on surface of primary phase. because of the less soluble behavior or when the solvent cannot contact with organics encapsulated in other inorganic matrixes (especially glass). with lots of voids and open spaces. On the other hand. Namely. These authors observed that the contaminant removal capacity of the fly ash was directly proportional to the CaO content. oxide. The tetrahedra make up a three-dimensional network. In reactions involving acid mine drainage with fly ash. Hence. direct doubling of element or ion concentration similar to a reaction of fly ash with demineralized water may not be observed. takes place from the surface of ash particles in lower pH range. its concentration in the process water on treatment of acid mine drainage with fly ash can readily be predicted with chemical equilibria models [267]. Considering the above mentioned. The dissolution of primary phase is slowed down as mass transport of ions and water between phases becomes diffusion controlled. by oxidation of a sulphide-rich mining waste [257. and carbonate classes may be leached. as well as the fact that this material. Release of anions such as SO2 4 and cations like Ca will result in precipitation of gypsum resulting in much cleaner water. Many important aspects of leaching behaviour of fly ash were reported by a number of researchers [245. This will result in precipitation of metal hydroxides. If a mineral solubility control exists for a species. Synthesis of zeolite Zeolites are crystalline aluminium–silicates. dissolved very slowly as they are trapped in glass and crystalline alumina silicates. 2) which may give rise to high CEC (up to 5 meq g1) when the open spaces allow the access of cations. These authors observed that generation of acidic leachates was prevented and inorganic contaminants significantly reduced. such as adsorption of molecules in the huge internal channels. The organic compounds identified in fly ash extracts include known mutagens and carcinogens. calcium oxalate. there must be a solid phase control on its concentration in solution. sulphates. highly soluble in water. portions of organics may remain in the residue. [261] investigated fly ash for neutralization of highly acidic heavy metal-laden oily waste sludge while Potgieter-Vermaak et al. and time. (3) immobilisation of mobile metals and other elements. It is these voids that define many special properties of zeolites. The substitution of Si (IV) by Al (III) in the tetrahedral accounts for a negative charge of the structure (Fig. Formations of artificial minerals and phases such as oxyhydroxides. more stable and less soluble mineral phases will thereafter precipitate. [260] studied the ability of fly ash to remove Cu2þ and Pb2þ in aqueous solutions. 11. this chemical treatment also leaches components associated with both organic and inorganic compounds in FA. 2) [7]. Mg. bonded materials are mainly used for upper base courses that are. Ahmaruzzaman / Progress in Energy and Combustion Science 36 (2010) 327–363 unstable. oxides and oxy-hydroxides with consequent adsorption or co-precipitation of trace metals. The main components of fly ash are anhydrous phases such as aluminosilicates and salts such as sulphates.258] and in passive treatment of acid mine drainage [259].253–255]. (2) forced extraction of mobile substances from fly ash. materials bonded with bitumen and cement tend to have significantly lower leaching abilities for two reasons: first. Zeolites may be found in natural deposits. Erol et al. A decrease in concentration when the FA: AMD ratio is doubled may therefore signify existence of solubility control for that element or ion. A complex mixture of organic compounds is also associated with fly ash particles. sulfide. the precipitates formed are largely amorphous [263. or altered during this procedure. Their structure is made up of a framework of [SiO4]4 and [AlO4]5 tetrahedra linked to each other at the corners by sharing their oxygens (Fig. and others are also possible. They pointed out that if a species concentration does not double when the L/S ratio is halved. Ca. the leachate from coal fly ash contains very low concentrations of polycyclic aromatic hydrocarbons (PAHs). there is no significant influence of hazardous elements on the surrounding waters and soil due to leaching. K and Fe which are also present in fly ash and will leach out on interaction with the AMD. destroyed. some unstable minerals from the chloride. and chlorides) are highly unstable at room temperature and pressure and in presence of water. has a very low permeability. The primary phases. In water. Leachability of heavy metals from the coal fly ash is relatively low and leaching extent is dependent on the conditions of water system. There are leaching procedures for the dissolution of the organic compounds of FA in 30–40% hydrogen peroxide. with group I or II elements as counter ions. Some of these phases (alkali metal oxides. The authors observed that fly ash can be used as a neutralization/fixation agent. generally associated with alkaline activation of glassy volcanic rocks. concentration of elements. or synthesized from a wide variety of high-Si and Al starting . the concentration of some constituent species in the leachate will be controlled by the solubility of the precipitating secondary mineral phases and concentration of other species will be controlled by their availability to the leachate solutions and by their diffusive flux into solution from the leaching of the primary phases with time [264– 266]. For example. usually 10–7 m/s. Several authors [268. pressure. and second. Several authors have investigated the capacity of fly ash to improve the quality of leachates generated by coal refuse [256]. The alkalinity of fly ash may not be as high as that of lime or limestone but availability in large quantities offers a cost effective method of neutralizing acid mine drainage. the AMD contains high concentration of SO42. 8H2O Na2Al2Si3. Factors affecting the yield .3O8.44$1.7 tons of zeolitic material in 8 h in a singlebatch experiment [284]. and a large pore volume [275].46H2O K9NaCaAl12Si24O72$15H2O NaAlSi2O6$H2O Na1. this is a suitable starting material for zeolite synthesis. including zeolites X and A.with a Si/Al substitution ([AlO4]5-) yielding a negative charge. (higher than 120 C). developed a synthesis strategy based on salt mixtures instead of aqueous solutions as reaction medium. Consequently. The potential industrial application of these zeolitic materials is varied.M. was the main reason to experiment with the synthesis of zeolites from this coal by-product. The solid residue from this attack was converted into classic zeolitic products by using conventional conversion method.86$4. zeolite Na–P1. such as.2$2. precursor of natural zeolites. at atmospheric and water vapor pressures. The synthesis of zeolites from fly ash is classified into direct and non-direct synthesis.3 Å) accounts for low potential application for both molecular sieving and ion exchange. Due to the presence of high content of reactive phases. Sodium or potassium hydroxide solutions with different molarity. pressure. Under these conditions.287].1$5H2O Na2Al2Si1. Gas adsorption: selective absorption of specific gas molecules. Since the initial studies by Holler and Wirsching [275]. Fly ash has a high Si/Al ratio. Zeolitic product Chemical formula JCPDS NaP1 zeolite Nap zeolite Phillipsite K-chabazite Zeolite F linde Herschelite Faujasite Zeolite A Zeolite X Zeolite Y Perlialit Analcime Hydroxy-sodalite Hydroxy-cancrinite Kalsilite Tobermorite Na6Al6Si10O32$12H2O Na3. Park et al.25H2O NaAlSi1. zeolites P. hydroxy sodalite and analcime were obtained with 4–10 M NaOH solution. volcanic rocks. and as replacement for phosphate in detergents [276]. a high selectivity for polar molecules. As a consequence of the peculiar structural properties of zeolites.8$6.08Al2Si1. high-pore volume zeolites. mainly as adsorbents for removal. since. developed a two-stage synthesis procedure that enables the synthesis of >99% pure zeolite products from high-Si solutions from a light alkaline attack of fly ash. This interesting process has limitations. X and Na–P1 were obtained with 2–4 M NaOH solution. relatively high temperatures (125–200 C) applied to dissolve Si and Al from fly ash particles. these minerals have important industrial applications. Table 6 showed the types of zeolite synthesized from coal fly ash.46$3. To avoid the synthesis process with the generation of wastewater.07H2O NaAlSi2. such as. [287]. radioactive wastes and gases.3 Å) and high CEC (5 meq/g).43O6. Idealized structure of zeolite framework of tetrahedral [SiO4]4. and clay minerals [273.7H2O NaAlSi1. many of the high-CEC and large pore zeolites (zeolites A and X) cannot synthesized. Fusion with sodium hydroxide prior to hydrothermal reaction was applied by Shigemoto et al. given intensive research on zeolite growth in geological materials.292. aluminosilciate glass. fly ash was hydrothermally treated with an alkaline solution. then synthesis yield is reduced considerably and a very long activation time is required. Zeolite was obtained by hydrothermal treatment of fly ash [272].6Si12.274]. The lignite fly ash and rice husk ash were also used as raw materials for ZSM-5 zeolite synthesis [295]. and consequently a cation exchange capacity [7]. 2. This alkaline conversion of fly ash is based on combination of different activation solution/fly ash ratios. For non-direct synthesis [286. The zeolite X has a large pore size (7. At temperature. they have a wide range of industrial applications [271] mainly based on: Ion exchange: exchange inherent Naþ/Kþ/Ca2þ for other cations on the basis of ion selectivity. A promising approach to improve the utilization of fly ash is to convert it into low-grade zeolites.1O4. These extracts were used as the starting material for faujasite synthesis at 60–90 C and time period of two– five days. instead of blend zeolite/residual fly ash particles obtained from other strategies. and high specific surface area of fly ash. [293.68O7. The time of activation (from hours or days to minutes) can be significantly reduced for zeolite synthesis using microwave-assisted hydrothermal process [281]. Several studies [277.294]. which allows the synthesis of low-Si zeolites with a high ion exchange capacity. Moreover. with temperature. waste waters. At temperature. up till now. Fig. The zeolite contents of resulting material varied widely (40– 75%) depending mainly on activation solution/fly ash ratio and reaction time. For direct synthesis [277–285]. while hydroxy sodalite and zeolite-Y were obtained with 4–10 M NaOH solution. Water adsorption: reversible adsorption of water without any desorption chemical or physical change in the zeoltie matrix.68O7. may be obtained in this process. only low-CEC zeolites are obtained to high temperature needed in the activation process. and reaction time to obtain different types of zeolite. [288–290] to improve the conversion of fly ash into Na–X Zeolite.44$1. such as. many patents and technical articles proposed different hydrothermal activation methods for the synthesis of different zeolites from fly ash.4O32$12H2O K2Al2Si3O10$H2O K2Al2SiO6$H2O KAlSiO4.23O4. The compositional similarity of fly ash to some volcanic material. If temperature is reduced. materials. from 80 to 200 C and 3 to 48 h have been combined to synthesize up to 13 different zeolites from same fly ash [284]. Ahmaruzzaman / Progress in Energy and Combustion Science 36 (2010) 327–363 345 Table 6 Zeolites and other neomorphic phases synthesized from fly ash and Joint Committee of Powder Diffraction Standard (JCPDS) codes for XRD identification. silica and alumina were extracted from fly ash with hot alkaline solution and this resulted in the mixture of silicate and aluminate extracts. This process has advantages of producing pure zeolitic material.293] examined the efficiency of Na and K-Zeolite synthesis after alkaline activation of fly ash in closed systems for short activation periods (8–100 h). This potential use of fly ash has an important background. This methodology was applied at a pilot plant scale for the production of 2. which make it an interesting molecular sieve and highcation exchange material. The small pore size of hydroxy-sodalite (2.6Al3. All methodologies developed are based on the dissolution of Al–Si-bearing fly ash phase with alkaline solutions (mainly NaOH and KOH solutions) and subsequent precipitation of zeolitic material. The main limitation of the processes for synthesizing zeolites from fly ash is to speed up reaction. Hollman et al.8H2O Na14Al12Si13O51$6H2O KalSiO4 Ca5(OH)2Si6O16$4H2O 39-0219 34-0524 30-0902 12-0194 25-0619 31-1271 12-0228 43-0142 39-0218 38-0239 38-0395 19-1180 31-1271 28-1036 33-0988 19-1364 (lower than 100 C). high water consumption and need for high activation periods. the time needed to obtain a high synthesis yield is inversely proportional to the glass content. lime). and initial pressure were investigated. The zeolitization of coal ash on a semi-industrial scale was conducted by Kikuchi [6]. However. . 3 and 5 M). varying activation agent (mainly KOH and NaOH). licensed by the KEM Corporation [297]. in addition to less water consumption. A pilot plant. 210 C.8–200 without TPABr. by increasing both parameters. chabazite.2 to 3. A. Querol et al. The determination of CEC value and comparison of pure zeolite is recommended for a semi-quantitative estimation of zeolite contents of synthetic materials. simultaneous removal of ammonium and phosphate from aqueous Fig. [7] reviewed the synthesis of zeolites from fly ash. The zeolite obtained from pilot plant is not inferior to conventional method. solution concentration (0. low-CEC zeolites such as hydroxy-cancrinite and hydroxy-sodalite are obtained. total dissolution of quartz and mullite is not achieved. the holding time. The high Al (III)/Si (IV) ratio of these zeolites accounts for the high CEC of some of them such as NaP1. sodium silicate solution was added to adjust the SiO2/Al2O3 mole ratio in raw ash. and 0. 3. KM. with special emphasis on the experimental conditions to obtain high cation exchange capacity (CEC) zeolites. fly ash activation is usually carried out in digestion bombs or autoclaves. but longer reaction times (24–48 h) are required to obtain similar synthesis yields from highmullite or quartz fly ash. for higher aluminum–silicate glass content. was developed.299]. A simplified process flow diagram is shown in the Fig. Owing to this high CEC (up to 5 meq g1 of some pure zeolites). They provided an overview on the methodologies for zeolite synthesis from coal fly ash. and optimal conditions were found to be 2. 11. quartz. High-glass fly ash is zeolitized in short period (6–8 h). such as..1. magnetite. pressure (the vapor pressure at the temperature selected). The highest synthesis yields are obtained in 12–24 h using a high-activation solution/fly ash ratio (10–20 ml/ g) due to total dissolution of mullite. the presence of tetrapropyl ammonium bromide (TPABr. Zeolite synthesized from fly ash has the ability of immobilizing phosphate from wastewater [298. However. Thus. in spite of small amount of NaOH charge. Thus.10 dm3/kg of liquid/solid. The use of lower activation solution/fly ash ratio (2 ml/g) led. and solution/sample ratio (1–20 ml/g). Conversely. and the glassy matrix. Suitable operational parameters of the process were investigated using a test unit. i. dried at room temperature and analyzed by XRD. Zeolite synthesized from fly ash can be utilized in the treatment of wastewater. A new process for converting coal fly ash into an artificial zeolite is described [296]. temperature (100 and 200 C). or chabazite.5 mol/dm3 of NaOH.e. Process flow of zeolitization plant (1. 3. Reaction time required for synthesis yield is inversely proportional to aluminum–silicate glass content of fly ash.346 M. when following conditions were used: SiO2/Al2O3 mole ratio. holding temperature and time.5. sodium hydroxide charge from 2. to a drastic reduction in the activation time. and faujasite. F. 4 h and the initial pressure. X. low temperature and concentration allows the synthesis of high-CEC zeolites.%.5 tons: hour) [6]. Most studies showed that NaOH solutions have higher conversion efficiency than KOH solutions under same temperature.6 m3 of vessel was tested. In most studies. The zeolite P was synthesized at SiO2/Al2O3 mole ratios of 2. herschelite. The zeolites obtained from a pilot plant had a higher cation exchangeable capacity than test unit and were comparable to zeolites prepared using a conventional method. Ahmaruzzaman / Progress in Energy and Combustion Science 36 (2010) 327–363 of ZSM-5 zeolite synthesized from fly ash. and resistant aluminum–silicate phases. 1. and the grain size distribution. NaP1. 4A. For the synthesis of ZSM-5 zeolite.88–1. shorter activation periods and lower solution/fly ash rates are needed to reach high yields of zeolite. intensive research has been carried out on the potential application of the zeolites synthesized from fly ash. The process is comprised of a high-temperature operation and water removal during the operation. such as. a new zeolite production process. The conversion efficiencies are dependent on non-reactive phases (mainly hematite. these zeolites have a high potential in water decontamination. Recently. The yield of ZSM-5 zeolite was 59 wt. and a detailed description of conventional alkaline conversion processes. As previously stated.9 mol/kg-CFA. the holding temperature. Both temperature and concentration of the activation agent have a very important influence on the types of zeolite obtained. 2. having a 0. The zeolitic material is filtered and washed with water. Therefore. such as mullite and quartz. 40. 4 bar. Application of zeolite synthesised from fly ash Simultaneously with the development of synthesis methods. this process suffers from a number of disadvantages.5–3. the SiO2/Al2O3 mole ratio. Most zeolites reported in the Table 6 obtained from specific fly ash. conversion time (3–48 h). the structure-directing material for ZSM-5 zeolite synthesis). Zeolite was synthesized from Class C fly ash by molten-salt method. medium and low-calcium fly ash and this behavior was explained by reaction of phosphate with calcium and iron components.4 times as a result of the conversion of fly ash to zeolite. while the treatment by concentrated H2SO4 (>0. Naþ (<25%).1 mg/g) than activated carbon (4. Several authors have reported the utilization of fly ash synthesized zeolite for the removal of heavy metals from wastewater.9 mol/L) resulted in a limited maximum phosphate immobilization capacity (PIC). Naþ (<20%). Increase in dissociated Fe2O3 and specific surface area probably accounted for enhancement in PIC of synthesized zeolites compared with corresponding fly ash. The adsorption capacity of ZFA was significantly improved. followed by Ca2þ(60–85%). silica gel (0. which is ascribed to small pores in zeolite frameworks.6 420. The removal performance and the selectivity sequence of mixed metal ions (Co(II).6 mg/g).01 mol/L H2SO4 improved the removal efficiency of phosphate by ZFA at all initial phosphorus concentrations. and the product obtained. ZFA can be used in the simultaneous removal of NHþ 4 and phosphorus at low concentrations in simulating real effluent.45 90. To develop an effective technique to enhance removal efficiency of phosphate at low concentrations. which was 2–3 times higher than those of synthetic zeolite P.58 mg lead/g-zeolite and 95.34 mmol Cs/g.1 times higher than activated alumina. Ahmaruzzaman / Progress in Energy and Combustion Science 36 (2010) 327–363 solution by zeolite synthesized from fly ash (ZFA) is possible.01 mol/L of H2SO4). and Mg2þ(<5%). Cr(III).5 mg/g. and used for the removal of metal ions.6 97. The removal of arsenic. which was 2.4 mg/g). zeolite fly ash (ZFA) was used as an adsorbent for removal of arsenate from water [303]. radiocesium [306]. At low initial phosphate concentrations. It was observed that the adsorption capacity of zeolites was generally lower than activated alumina (16. High selectivity. Metals Adsorbent Zn2þ Cd2þ Fly Fly Fly Fly Fly Fly Fly Fly Fly Fly Fly Pb2þ Cu2þ Ni2þ Cr3þ Co2þ Csþ ash ash ash ash ash ash ash ash ash ash ash zeolite zeolite zeolite zeolite zeolite zeolite zeolite zeolite zeolite zeolite zeolite Adsorption capacity (mg/g) 4A X X 4A X 4A 4A 4A 30. The existence of exchangeable Ca2þ on zeolite surface is critical to precipitate phosphate in aqueous solution [298. Al-. Surface-modified zeolite material has been developed from commercial zeolite. hexadecyltrimethylammonium bromide and tetramethylammonium bromide [310]. Treatment by 0. The removal mechanism of metal ions was by adsorption and ion exchange processes.0 mg/g).78 70. was investigated [305].6 mg cadmium/g-zeolite.2 to 7. It was shown that Al3þZFA had the highest removal efficiencies (80–98%) for ammonium. Cu(II) was found to be generally controlled by intraparticle diffusion step at all concentration range examined in this work. and Fe-ZFA by salt treatment and the simultaneous removal of ammonium and phosphate by ZFA saturated with different cations was investigated [302].1 mg/g). Zeolite synthesized from fly ash can also be utilized in the removal of heavy metals from wastewater. by treating it with surface modifiers.46 mg/g). zeolite NaY (1. Phosphate immobilization capacity (PIC) of the synthesized zeolites and corresponding raw fly ash was determined using an initial phosphate concentration of 1000 mg/L [300].and Fe3þ-ZFA approached 100%. It was concluded that through a previous mild acid treatment (e. However. ZFA was modified with acid treatment and simultaneous removal of ammonium and phosphate in a wide range of concentration was investigated [301].72 443. and fly ash-based zeolite. The difference in phosphate removal efficiency was explained by the adsorption mechanisms. External mass transfer step seemed take part as a rate limiting step for sorption of Pb(II) at low initial concentration. Mg2þ) and acidic pH value (in the case of Fe3þ) inhibited the sequestration of ammonium. Ca2þ. Zn(II) and Ni(II)) in aqueous solution were investigated by adsorption process on pure and chamfered-edge zeolite 4A prepared from coal fly ash (CFA).96 41. Ca2þ (40–54%). respectively. In another study. respectively. ZFA showed a higher adsorption capacity (5. and related co-disposal filtrates as low-cost adsorbent material. after loaded by alumina via a wet-impregnation 347 Table 7 Summary of adsorption of metals on fly ash based zeolite. commercial grade zeolite 4A and the residual products recycled from CFA [308].9 Temperature ( C) 20 20 25 References [308] [307] [309] [307] [309] [308] [309] [308] [306] method.M. such as. and natural mordenites. lead and cadmium [307]. The Toxicity Characteristic Leaching Procedure (TCLP) leachability tests indicated that spent ZFA and alumina-modified ZFA complied with the EPA regulations for safe disposal.80 95. Table 7 summarizes the results of the important metals investigated using zeolite-synthesized fly ash.61 50. The modified ZFA (ZFAAl50) with optimum alumina loading showed an adsorption capacity of 34. The synthesized zeolite was explored to establish its ability to remove Pb(II) and Hg(II) from aqueous solution. The maximum removal of phosphate occurred within different pH ranges for zeolites which were synthesized from high. The adsorption process is pH and concentration dependent. and low sorbent dose. Cd(II). The sorption rate and sorption capacity of metal ions could be significantly improved by increasing pH value. and used as an effective adsorbent for the removal of Cu(II). and zeolite 5A (4. The specific surface area increased 26. Treatment with more concentrated H2SO4 led to the deterioration of ZFA structure and a decrease in the cation exchange capacity. on the other hand was controlled by both external mass transfer and intraparticle diffusion steps at all range of initial concentration. The utilization of zeolites synthesized from fly ash (FA). The process was controlled more significantly by intraparticle diffusion step at high initial concentration.6 times) following the synthesis process. there was no significant change of Ca and Fe content following conversion of fly ash into zeolite. Cu(II). The synthesized zeolite was effective in reducing the Pb(II) and Hg(II) concentrations by 95% and 30%. Adsorption capacity for lead and cadmium was 70. followed by Mg2þ (43–58%). Although calcium and iron components were mainly involved in phosphate immobilization. Fly ash was converted to zeolites by hydrothermal treatment. The adsorbent was evaluated for removal of arsenic and chromate anions. when the initial concentration for both ions was 100 mg/L. It was concluded that ZFA could be used in simultaneous removal of NHþ 4 and phosphate at low concentrations with presaturation by an appropriate cation such as Al3þ through salt treatment.86 8. The coal fly ash (CFA) was modified to zeolite X.0–89. The sorption of Cd(II). Na-ZFA (zeolite synthesized from fly ash) was converted into Ca-. The effects of different parameters like pH and presence of other constituents are described. Maximum uptake capacity was 3. and Pb(II) [309]. and high adsorbent dose. Mg-.61 13.g. The effectiveness of the modified fly ash bed for the control of arsenic was demonstrated by taking different quantities of arsenic(III) and arsenic(V) salts. the efficiency of phosphate removal by Al3þ. faster kinetics and high .299]. Results showed that there was a remarkable increase in PIC (from 1. Both alkaline pH values (in the cases of Naþ. 0. from drinking water by filtration through modified fly ash bed is also reported [304]. and Fe3þ (<1%). Relatively higher adsorption capacity of ZFA than zeolite NaY and 5A was attributed to the low Si/Al ratio and the mesoporous secondary pore structure of ZFA. Newly developed admixtures allow lowering the water/cement ratio to very low levels without loss of workability.05 and 3. There are few studies on the effect of steam curing on high-volume Class C fly ash concrete. To overcome this shortcoming. It has been used particularly in mass concrete applications and large volume placement to control expansion due to heat of hydration and also helps in reducing cracking at early ages. The use of fly ash in concrete enhances the workability of concrete and being widely recommended as partial replacement of cement. Fly ash was modified by hydrothermal treatment with NaOH to hydroxysodalite zeolite [313]. i. if fly ash concrete is allowed to cure fully. Ahmaruzzaman / Progress in Energy and Combustion Science 36 (2010) 327–363 adsorption capacity ensure cost effectiveness of these materials compared to other conventional materials for dearsenification. the early strength development of fly ash concrete can be accelerated to achieve the desired performance. consequently leading to organic partitioning. Surface modified zeolite from fly ash is being used for adsorption of phenol and o-chlorophenol from wastewater [311]. Several studies are being conducted to better understand the complexities of alkali aggregate reactivity and sulphate resistance with respect to fly ash in concrete. benzothiophene etc. Construction work/industry Utilization of fly ash appears to be technically feasible in the cement industry. The availability of high-lime fly ash containing compounds found in cement has led to high-strength concretes produced by the addition of fly ash and plasticizers. The utilization of fly ash is partly based on economic grounds as pozzolana for partial replacement of cement. and streets. i. a material is needed. Extended hydration period makes the material more sensitive to curing conditions. decreasing the water:cement ratio. . HUSY. respectively. These problems may be solved by using various methods such as steam curing. especially under cold weather conditions. Class C fly ash may not lower the heat of hydration. Adsorption is thus ascribed to be a surface effect rather than involving incorporation into the channels of hydroxysodalite structure. with bituminous-type fly ash. The presence of salts has a substantially detrimental effect on adsorption of phenol and o-chlorophenol. the high-calcium fly ash is quite suitable in Portland cement products. A decrease in water demand. By incorporation of superplasticizers (SPs). In mass concrete. The results suggested a potential of zeolites derived from coal fly ash for removal of refractory sulfur compounds.5. Acidic-type interactions between sulphate ions and calcium hydroxide also lead to strength and mass loss. respectively. which is equal to CaO5/Fe2O3 oxide analysis percentages. The setting and hardening rates of fly ash concrete at early ages are slower. An improvement of the packing of particle size decreases air entrainment in the concrete. including (1) replacement of cement in Portland cement concrete (2) pozzolanic material in the production of pozzolanic cements. It was found that GIS with higher specific surface area and average pore volume had superior performance to other synthesized materials. fly ash should improve sulphate resistance. more dense paste and pozzolanic reaction. and therefore improved packing. chemical admixtures are essential components of the concrete mixtures. Because of the presence of cementitious compounds of calcium and a reactive glass.29 and 1. such as calcium monosulfo-aluminate and calcium aluminate hydrate. This may attributed to hydrophobicity imparted by surfactant molecules on the surface of fly ash zeolite. High-strength and high-performance concrete can also be made with Class F fly ash. such as thiophene. The cation exchange capacity of the modified ash was significantly increased over that of the raw fly ash. Nowadays. Adsorption of phenol on SMZ-Y was 4. It was reported that Saskatchewan lignite fly ash concrete increases sulphate resistance [314]. The advent of cementitious. Cement is the most cost and energy intensive component of concrete. As noted in his review paper on this subject [316]. reduced bleeding. For o-chlorophenol. The utilization of fly ash in concrete produces less permeability because of the spherical particles. particularly when Class F fly ash is used. The potential of fly ash based zeolites for adsorption of thiophene and benzothiophene from n-hexane solution was investigated [312]. Generally. it is concluded that zeolite from fly ash can not be applied in high-value applications. Fly ash increases resistance to corrosion. the agents responsible for concrete expansion and cracking are alumina-bearing hydrates. NaY. The ball bearing effect produced by the spherical fly ash particles has resulted in better pumpability of concrete and easier finishing with trowels and other tools. There has been much concern about sulphate resistance of concrete containing high-lime fly ash. The comparison of adsorption of phenol and o-chlorophenol on commercial zeolite-Y.with high-percentage replacement of cement with fly ash. Thus. and lower evolution of heat. lower water demand for similar workability. Research with other high-lime fly ash has produced conflicting results with respect to sulphate resistance. 12. The unit cost of concrete is reduced by partial replacement of cement with fly ash. the efficiency is higher by a factor of 2. driveways. and ZSM-5 obtained via the conventional synthesis methods. there is a lower heat of hydration compared to straight Portland cement concrete. Modified fly ash adsorbed a cationic dye (methylene blue) to a much greater extent than an anionic dye (alizarin sulphonate). and ingress of corrosive liquids by reacting with calcium hydroxide in cement into a stable. Traditionally. R. such as.348 M. and cancrinite (CAN). Although research has indicated that decreased air entrainment adversely affects initial freeze than durability of the concrete. This also reduces the cost of construction.e. the effects are minimum and the concrete mix will perform satisfactorily. and (3) set retardant ingredient with cement as a replacement of gypsum. Mehta [316–319] has discussed the factors that contribute to attack of sulphates on fly ash concrete. fly ash based zeolite (FAZ-Y) and surface modified fly ash based zeolite (SMZ-Y) were studied. the long term ultimate mechanical properties of fly ash concretes are higher than those of plain Portland cement concretes. gismondine (GIS). Adsorption capacity of developed zeolites was compared to those of commercial zeolites. The zeolites obtained were sodalite (SOD).8 for FAZ-Y and commercial zeolite-Y. and partly because of its beneficial effects.24 times higher than the FAZ-Y and commercial zeolite-Y. When R is less than 1. 15–25% of the cement was replaced. Research showed that fly ash used as an additive to Portland cement has a number of positive effects on the resulting concrete. There are essentially three applications for fly ash in cement. Saturation adsorption revealed that capacity of fly ash for methylene blue had increased 10-fold during modification when compared to raw ash. beta. which can improve the workability without comprising strength. Fly ash concrete provides much strong and stable protective cover to the steel against natural weathering action. which are attacked by the sulphate ion to form ettringite and calcium trisulfoaluminate.e. Exhaustive research has been conducted on fly ash admixture concrete and its properties. high-lime fly ash has permitted normal replacements of 25–40% and up to 75% for parking lots. but used for some of the low value applications that utilize the good ion exchange capacity of such zeolite (but this ion exchange is almost non selective and therefore can not be used as catalysts). The major drawback of fibre reinforced concrete is its low workability. Dunstan [315] has proposed a sulphate resistance factor. Cr. I and F fly ash with water. Results up to 275 days of testing have indicated that high replacement levels of cement with fly ash were highly effective in inhibiting alkali–silica reaction [325]. The treatment of C-FA with an aqueous CaCO3 solution results in a dramatic improvement in the setting time and the setting profile on C-class FA. The compressive strengths of dam concrete with 50% of fly ash in 90 days are higher than those with 30% of fly ash or without fly ash. since it is believed that sulphate ions necessary for prolongation of the setting process (commonly provided by gypsum) could be provided by fly ash enriched in sulphates. containing high volume of Class F fly ash exhibited excellent mechanical properties. and reinforced cement concrete construction. the setting process is no longer dependent on the particle shape. C-FAH2O) results in the extraction of Na and Ca with a concomitant increase in surface area and a performance similar to untreated I-FA and F-FA. Siddique [333] reported that Class F fly ash can be suitably used up to 50% of cement replacement in concrete for use in precast elements.2 wt% of CaCO3 solution results in dramatic increase in setting time. Bouzoubaaˆ et al. Superplasticized high-volume fly ash concrete. [332] examined the effects of fine aggregate replacement on the rheology. Blending of Class C fly ash with Class F fly ash showed either comparable or better results than either of the control mixture without fly ash or the unblended Class C fly ash [331]. splitting tensile and flexural strengths. and the shrinkage and expansive strain was reduced significantly–about 33% and 40% less than the specimens without fly ash. The use of high volumes of Class F fly ash as a partial replacement of cement in concrete decreased its 28day compressive. packing and dispersion of the fly ash and cement. Zhang et al. Oner et al. while acid treatment of C-FA results in a material with completely undesirable setting properties. [336] showed that except for resistance of the concrete to the deicing salt scaling. and showed no adverse expansion when reactive aggregates were incorporated into concrete [324]. whereas in case of lower-calcium fly ash. compressive strength. Fly ash may decrease the deformation of dam concrete with 50% of fly ash. The original calcium hydroxide was soluble. High volumes of Class C and Class F fly ash can be used to produce high-quality pavements in concrete with excellent performance [330]. Lupu et al. These results in decreased setting time. Abrasion resistance of concrete made with Class C fly ash was better than both concrete without fly ash and concretes containing Class F fly ash [329]. The low-lime fly ash was used to develop chloride-resistant concrete by improving its physical resistance to the ingress of chlorides and binding capacity of these ions in the cover zone [339]. accelerated strength development. mechanical properties and durability of concrete made with this blended cement were superior compared to the ungrounded fly ash and cement concrete. The study suggested that the binders are eminently suitable for partial replacement (up to 25% of the cement in concrete) without any detrimental effect on the strength. [342] activated fly ash chemically by adding industrially produced quicklime. The chemical treatment of Class C fly ash with a 0. Antiohos et al. Pb. Ravina and Mehta [321] reported that by replacing 35– 50% of cement with fly ash. Singh and Garg [334] studied the cementitious binder from fly ash. . [320] studied the leachability of trace metal elements from fly ash concrete. when water-tocement ratio was maintained. Antiohos et al. This type of concrete contains more than 50% of fly ash by mass of total cementitious materials. Hwang et al. HNO3 and aqueous CaCO3 [341]. modulus of elasticity. and the rate and volume of bleeding water was either higher or about same compared with the control mixture. The utilization of fly ash in the construction of concrete dams was investigated [338]. Concrete. The performance of CaCO3 treatment appears to be a consequence of each fly ash particle being provided with necessary Ca prior to hydration without being dependant on cement-fly ash particle interactions. No gypsum was added in the mixtures. Thus. Malhotra and colleagues [322–328] reported extensively on high-volume fly ash concrete. and carbonation properties of fly ash and mortar. thereby reducing permeability of the concrete. chemical activation of reactivity of fly ash is an effective method to increase the use of fly ash in concrete. They modified the class C. and superior stability during the induction period for cement slurries. thereby reducing the possibility of leaching of calcium hydroxide from the concrete. Na2SO4 or CaCl2 accelerates pozzolanic reactions. such as. and thereafter acted inhibitory with respect to its reactivity development. [340] investigated the use of chemcially modified fly ash to control the setting of cement. quicklime had a positive impact only during the very early stages of hydration. Cu. Test results showed that rheological constants increased with higher replacement level of fly ash and that. there was 5–7% reduction in water requirement for the designated slump. Addition of chemical activators. All samples tested exhibited satisfactory initial and final setting times and decent compressive strength values. Air-entrained highvolume fly ash concrete exhibited excellent characteristics regardless of the type of fly ash and cements [327].M. whereas the calcium silicate hydrate is less soluble in fly ash concrete. High-volume fly ash concrete has emerged as a construction material in its own right. and abrasion resistance of the concrete. and found that none of the trace metals analyzed (As. good durability with regard to repeated freezing and thawing. It was found that the setting properties of the cement/fly ash mixture enhanced by changing morphology and surface chemistry of fly ash particles. containing up to 60% of fly ash of total cementitious materials had poor abrasion resistance than concrete without fly ash [326].. The presence of quicklime accelerated the reaction rate of high-calcium fly ash. The acid (HNO3) treatment of I-FA and F-FA results in the formation of an inert filler-like material. reaction products tend to the filling of capillary voids in the concrete mixture. C–S–H gel and C4AH13. Addition of fly ash as an admixture increased early-age compressive strength and long-term corrosion resistance characteristics of concrete [328]. since simply washing with water (i. when compared to the reference specimen containing only gypsum and no fly ash. and optimum usage of fly ash in concrete. the strength development and carbonation properties were improved. and changes pozzlanic reaction mechanisms between fly ash and lime [343]. Thus. respectively. Researchers have modified fly ash to increase the setting properties of cement. especially with a high percentage of fly ash. They studied the effect of leaching conditions. Fly ash can be used in the range from 45% to 70% in formulating these binders along with other industrial wastes to help in mitigating environmental pollution. The enhancement observed for the treatment of C-FA with aqueous CaCO3 solution is not a consequence of the water solution. and increased strength of materials containing fly ash. In addition to calcium silicate hydrate being less soluble.e. in contrast. [335] 349 conducted a study on strength development of concrete containing fly ash. very low permeability to chloride ions [322–324]. [337] investigated the properties of a series of blended cements prepared by mixing clinker with a fly ash of high-sulphate content. The development of binder takes place through the formation of ettringite. Se and Zn) in the leachates from fly ash concrete exceeded the regulated concentration levels specified in the toxicity characteristic leaching procedure (TCLP) test. Ahmaruzzaman / Progress in Energy and Combustion Science 36 (2010) 327–363 cementitious compound of calcium silicate hydrate. Many researchers have used high volume of Class C. Cd. and Class F fly ash in concrete. the treatment has no effect on the set time for F-FA and reduces the set time and appears to result in an even more nonideal induction setting curve as compared to the untreated C/I-FA. It was found that 50–60% of mechanically activated fly ash can be used as replacement for clinker with strength higher or comparable to commercial cement. i ¼ C3S. consistency setting time.350 M. the finer particles may more completely react than the coarser particles of fly ash. It was shown that a nonstandard fly ash can also be used in concrete. Zhang et al.352]. it provided excellent strength. RPC has excellent freeze–thaw resistance with no sign of damage up to 600 cycles according to ASTM C 666 test procedure. The observation based on isothermal conduction calorimetric studies are quite revealing in this context. The study revealed that mechanical activation of fly ash has an indirect bearing on the hydration of cement phases. Adequate early strengths and set times are obtained by using high range water reducers to achieve a very low water/cement ratio. In order to increase considerably the utilization of fly ash. The effect of these mineral admixtures on compressive strength of RPC was investigated under autoclave curing. sulfate attack. [365] studied the effects of autoclaving under saturated vapor at 180 C on the physical and mechanical properties of reactivepowder mortars reinforced with brass coated steel fibers. Shaheen and Shrive [366] investigated the freeze–thaw resistance of RPC. So. The reactivity of fly ash can be increased through mechanical activation. after 3 days and 28 days of hydration. and will perform comparable to highly reactive pozzolans. such as resistance to alkali sulfate reaction.g. and must be cost effective. crushed quartz and silica fume. tri-calcium silicate (C3S) and tri-calcium aluminate (C3A). and its bearing on the hydration of clinker phases. Roller compacted concrete (ROCC) application showed that usage of fly ash in ROCC production was a wide spread practice. the cement samples meet all other criteria. ultra fine fly ash is used at a replacement rate of 5–15% of the cement weight. It increases abrasion resistance of concrete [357]. Autoclave curing yielded flexural strength of 30 MPa and compressive strength of 200 MPa. The reduced particle size means that the pozzolanic reaction. and at the same time have high early strengths. is accelerated. for lightweight concrete production was developed at The College of Judea and Samaria (Ariel. it is necessary to advocate the use of concrete that will incorporate large amounts of fly ash as replacement for cement. [361] showed that a non-standard fly ash could also be used in concrete. The overall effect of mechanical activation of fly ash on cement strength may result from the formation of compact microstructure. As compared to typical fly ash. such as. with a mean particle diameter ranging from 20–30 micrometers. e. Ahmaruzzaman / Progress in Energy and Combustion Science 36 (2010) 327–363 The typical use of fly ash in Indian Pozzolana Portland cement (PPC) is in the range of 15–25%. [368] found that RPC has a good repair and retrofit potentials on compressive and flexural strength. Lee et al. C3A). the ASTM C-618 [359] restricts the amount of SiO2 þ Al2O3 þ Fe2O3 (SAF) to 50% for high-calcium fly ash. Rougeau and Borys [367] showed that ultra high-performance concrete (UHPC) can be produced with ultra fine particles other than silica fume. Both AASHTO M 295 (ASTM C 618) Class C and Class F fly ash have their own specific advantages when used as a cementitious material in concrete. A novel technology of combined utilization of high volumes of both coal ash–bottom ash and fly ash. Cement dosage of RPC is generally over 800–1000 kg/m3. The exact ratio of the blend will depend upon the specific fly ash and their desired behavior in the concrete. such as. Further studies are required to understand the exact mechanism of hydration. showed a high degree of correlation with calorimetric results. Mechanical activation of fly ash results into a significant increase in the early strength of cement. such concrete will have to demonstrate performance comparable to that of conventional Portland cement concrete. C3A). Higher usage of fly ash is restricted. [369] demonstarted that cement and silica fume content of RPC decreased using fly ash.356]. At these dosage levels. especially the early strength. and reduces alkali aggregate reaction [358]. A high amount of cement not only affects the production costs. heat of hydration [354]. CANMET developed a concrete incorporating . strength and shrinkage [351. Typically. dams. which is normally a slow process. The effect of mechanical activation depends on the type of activation device. Yazici et al. HVFAC has a lower cost and is more durable than conventional concrete. However. The basic principles for the development of RPC have been explained by the Richard and Cheyrezy [262–363]. because of increased lime reactivity. sulfate attack. Concrete durability properties. it has been demonstrated that ultra fine fly ash contribute more to concrete strength gain and permeability reduction than common AASHTO M 295 (ASTM C 618) fly ash. and affords improved resistance to alkali-sulafate reaction and sulfate attack. such as. Reactive powder concrete (RPC) is a rather new cement-based material developed through microstructural engineering. permeability and porosity of concrete [355. Recently. One way to achieve that is to blend Class C and Class F fly ash. For instance. It may be ideal to have a fly ash with a low to moderate LOI and that can be used to prepare a concrete that is very effective in resisting alkali sulfate reaction. Recently. Utilization of fly ash in accordance with its physical property and chemical composition is restricted by different standards. and corrosion are also enhanced by ultra fine fly ash. incorporation of mineral admixtures may positively affect the durability of concrete. Several successful field applications have been completed. and steel corrosion resistance of cement was similar to commercial cement.360] showed that Aberthaw fly ash did not conform to the relevant standard. roads. This is attributed to the low reactivity of fly ash [344]. and the time of maximum hydration rate (Ti. HVFAC refers to concrete where fly ash comprises more than 30% of the total cementitious materials. Furthermore. and different proportions of raw and mechanically activated fly ash was investigated. Kejin and Zhi [364] showed that maximum heat of cement hydration in binary/ternary cement (fly ash and/or ground granulated blast furnace slag) concrete decreased with supplementary replacement of cementitious material. hydration of cement formulations containing fixed amount of clinker (50%). due to a decrease in the strength of cement. The higher reactivity of mechanically activated fly ash has been exploited in developing the process of making PPC containing higher proportion of fly ash [345–347]. Massidda et al. limestone microfiller or metakaolin. Furthermore. using fly ash in concrete reduces bleeding [353]. Israel) [370–373]. Fly ash modified the properties of concrete in both fresh and hardened state including workability. This was reflected by change in the maximum hydration rate of the phases (Ri where i ¼ C3S. alhtough. The effects of compressive and flexural strength with RPC of 10-mm thickness are about 200% and 150% more than normal strength concrete. the durability and strength benefits that one observes with a typical fly ash at a late age (more than one year) can be attained at a much earlier age (less than 90 days) and with a smaller dosage of an ultra fine fly ash. ultra fine fly ash can be produced with a mean particle diameter of 1–5 microns. fly ash. such as silica fume. autoclave expansion. Replacing cement with mineral admixtures seems to be a feasible solution to these problems. as compared to commercial cement. and 70% for low-calcium fly ash. Apart from strength. It was observed that compressive strength. Atis [356. Further. Conventional RPC is composed of cement and very fine powders. and large floor construction [348–350]. namely. The exact mechanisms of the strength development in PPC containing mechanically activated fly ash are not understood completely. but also has negative effects on the heat of hydration and cause shrinkage problems. In 1985. and to have a significant impact on the production of cement. To assess the role of mechanical activation. and strength development in PPC prepared with mechanically activated fly ash. The inclusion of air as small. the filtrate containing these ions was added to an AEA solution and it immediately turned cloudy indicating that the surfactants precipitated.387]. leading to a reduced amount of AEAs stabilizing the entrained air [385. The aim of producing concrete. fly ash can be used and will give similar or improved properties compared to neat Portland cement binders. However. Air entrainment occurs during agitation of the concrete paste. these have tended to be in special situations where.379]. a possible route to minimising the increases in binder content required with fly ash is through reduced water contents and inclusion of these admixtures to maintain workability. An increased dosage of AEAs may compensate for the adsorption loss. It is shown that in other construction applications where cementitious binders are required. McCarthy and Dhir [374] have demonstrated that fly ash is generally under-utilised. A large part of the carbon surface is non-polar compared with the polar surface of the inorganic particles. who argues that modern surfactants create smaller bubbles with less spacing between each other in the concrete paste. and the amount. The unburned carbon. which with greater levels of a relatively slower reacting material will tend to be reduced. through a number of different methods. because at higher levels early strength of concrete may be reduced. e. An attempt has been made to consider methods for the continued use of fly ash as a binder through post-production processing if changes in the production process modify its properties. [389] investigated the impact on air entrainment from alkaline ions such as Ca2þ and Mg2þ. is controlled by air entraining admixtures (AEAs).e.386]. the cement characteristics. in particular with respect to durability. Adjustment to the constituent materials. Furthermore. This effect stabilizes the air bubbles. These provide considerable potential for substantial increases in fly ash utilisation. even in ashes acquired from the same power plant. Similar behavior was observed when a calcium containing fly ash was added to an . This provide active adsorption sites for the hydrophobic part of the surfactants. while these cements will boost the early strength of fly ash concrete. control of heat or properties other than strength has been important. This approach is attractive because it is more effectively using the 351 constituent materials. It has also considered how improvements can be obtained through combination with one or more other binder materials. and that is environmentally friendly. It is demonstrated that fly ash has a role to play in the development of high-performance concretes through the use of multi-binder combinations.377]. and not the inorganic fraction (mineral matter) of the fly ash. by which this can be extended. At this level. sub-millimeter air bubbles (less than 250 mm) makes the concrete more resistant toward damage from freezing and thawing and improves its workability and cohesion [375–377]. centres around minimisation of voidage as the binder matrix develops. the AEAs are strongly adsorbed by some fractions of the fly ash. On the other hand. A significant decrease in surfactant adsorption of a fly ash was observed. The composition and characteristics of fly ash have tended to dictate the way the material is used in concrete.g. Overcoming this potential restriction is a necessary requirement towards the use of higher fly ash contents in concrete for mainstream structural applications. without or only to a small degree affecting the production costs [378. excellent mechanical properties. in structural concrete fly ash levels of 30% of the binder content are common. which is approximately 5–6 vol%. which are able to form insoluble products with surfactants. The surfactants adsorb strongly to the air–water/cement interface. thus the carbon competes with the air/water interface. having their non-polar end toward the interior of the air bubble and their polar end in the aqueous phase or adsorbed on the surface of the cement particle [376]. It is believed that these routes are of importance towards developments in and achievement of high-performance concrete. the authors have attempted to show. Vinsol resin extracted from pinewood is one of the most effective AEAs among the natural surfactants. Several properties of concrete are improved when air is entrained. This can frequently be a critical parameter in relation to the management of site operations and overall economy of construction. it has been demonstrated that. but do not consider the size and shape of the binder particles. The utilization of fly ash in concrete has been reported to affect the required dosage of AEAs to entrain the proper amount of air in the concrete mixture [381–384]. tall oil) or based on synthetic chemicals [378]. which in the case of missing AEAs would coalescence into larger bubbles leaving the concrete mixture. low permeability. modern AEAs are mostly anionic in character [379]. too high air content reduces the strength of the concrete [376. and that which has been treated with moisture. These are typically aqueous mixtures of ionic or non-ionic surfactants derived from either natural sources (wood resins. The majority of mix proportioning techniques available for concrete tends to give coverage to the particle size distribution or grading of aggregate. Baltrus et al. For example. in almost all respects. Fly ash can be used more effectively in concrete by simple adjustment of the concrete constituent materials or through more refined concrete mix proportioning techniques. Experience with fly ash in structural concrete has generally seen the material used at levels of around 30% of the binder. then the demands on the developing matrix will be reduced and the process of producing a dense material should be more readily achieved. potentially allowing greater levels of material to be used. for example. but normal variations in ash properties give rise to large and unacceptable variations in entrained air [385. such as grouting and masonry. Ahmaruzzaman / Progress in Energy and Combustion Science 36 (2010) 327–363 large volume of fly ash that has all the attributes of high-performance concrete i. The advantage of combining fly ash with these materials is two-fold. [380]. after it had been washed with deionized water to remove soluble ions. Today. The dilution of cement with slow reacting fly ash will reduce the rate of setting and promote the development of a better hydrate structure. materials of high LOI. superior durability. are potentially simple routes to further exploiting fly ash. Where higher levels have been used. in particular the use of coarser fly ash. The active compound is the sodium salt of abietic acid (AAS). If this is controlled initially by simply considering the physical properties of all of the solid constituents and optimising their proportions to minimise voidage. A possible means of achieving this lies in the combination of fly ash with cement that exhibits high early strength characteristics or is fast reacting. with the dispersing effects of the super plasticizing admixture promoting the formation of a better hydrate structure and less surplus water in the concrete mix. particularly in relation to its application as a binder. less entrained air is needed to obtain a freeze– thaw resistance. use of chemical admixtures and the way the materials are proportioned. The required amount of air to prevent concrete from freeze–thaw damages has been discussed by Nasvik et al. beyond normal Portland cement. Helmuth [388] has summarized how variations in several properties of fly ash have been found. Instead of stabilizing the air– water/cement interface. As fly ash is slower reacting than Portland cement. similar or enhanced performance compared to that of Portland cement concrete of equivalent 28 day strength is possible. This can be with cements which are chemically composed or ground to a greater fineness to provide high early strength. use at higher levels can have a detrimental effect on early concrete strength. appears to be responsible for the adsorption of AEAs [385–387]. With this combination. Given the importance of efficiently using binders and the increased availability and use of super plasticizing admixtures.M. A model can be used as a tool to quantitatively predict AEA requirements. Methods to distinguish and separate soot from char need to be further developed in order to verify if soot contributes to the poor performance of some fly ash in concrete. both initial and over time. Gao et al. Approval of fly ash from biomass combustion as concrete additive may give rise to new problems with air entrainment in concrete. It is striking to note that none of the leachates from ASTM and USEPA tests exhibits heavy metal concentrations exceeding the drinking water standards. that patents have been drawn by Hurt et al. higher fineness of fly ash has been argued to lead to increased required dosage of AEAs [382]. Cd(II) and Cu(II). none of the studies compared the AEA adsorptivity of the fly ash before or after the cleaning process. price of ozone. ionic strength. Metal-laden fly ash can be incorporated into the cementitious mixture to a great extent without the risks of unacceptable delay of cement setting and excess heavy metals leachability from solidified products. Other compounds of fly ash. wetting/drying and freezing/thawing cycles. Ozonation. Therefore. Gao et al. However.5 wt% and it performed well in concrete. The fixed metals essentially did not leach out into water over extended periods. which is considered to be impractical by the authors [392]. and solidified by cement-based CFS technology to hard concrete blocks which should not pose any risk to the environment [409]. The LOI of the product was approximately 2. particles. The relative contribution of soot and char to poor fly ash quality is still an unresolved issue which need further investigation. especially in power plants where highly reducing combustion conditions are implemented. sulphate resistance. The latter observation is noted to be in agreement showing that less AEAs were required in Portland-cement mortars with increased alkalis [391]. Ca3(PO4)2 or Ca3(PO4)2 þ CaCl2 at optimal dosages so as to improve the setting. The disposal of metal-laden fly ash is a problem. used as immobilization agents for heavy metal ions in aqueous solution. thermal treatment and physical cleaning of carbon have been found to improve the fly ash performance for concrete utilization. respectively. However. have been reported by Gebler and Klieger [390]. Moreover. The matrix-disrupting effect of lead was eliminated by adding NaAlO2. [408] recommended the following potential subjects to be included in further work. Ahmaruzzaman / Progress in Energy and Combustion Science 36 (2010) 327–363 AEA solution. and Pederson et al. fly ash sales price. the surfactants were simultaneously adsorbed by the fly ash and the initially formed precipitate did slowly dissolve again. The recovered carbon product is often disposed in landfills [407].g. while thermal treatment in air requires more than 300 C. Steps should be taken toward a better understanding of the relationship between combustion conditions and fly ash quality. where both low NOx emissions and high-fly ash quality may be achieved. thermal post-treatment of fly ash has successfully been implemented in at least one case [393]. such as strength. which increases the oxygen population on the surface. Post-treatment methods have been applied to improve fly ash quality. Several studies have been published describing how carbon in fly ash can be reduced by physical cleaning [396–406] and many patents have been drawn. Separation processes can recover carbon from fly ash. The polar ends of the surfactants are oriented toward the particle making them still able to contribute to air entrainment.352 M. The same effect is seen in concrete pastes where the surfactants are adsorbed on the surface of cement particles and therefore. controlled by carbon properties such as porosity and surface complexes. which may influence the air entrainment in concrete. Weng et al. where fly ash with an average LOI on 12. but has in some cases been reported to interact with air entraining admixtures (AEAs). Nevertheless. However. Laboratory data indicated that increased SO3 or total alkalis (as Na2O). From the evaluation of laboratory data and economic calculations based on ozone requirements. can help in development of diffusion models for the AEAs into carbon in the concrete mixtures. fly ashes can show poor performance in concrete utilization even at LOI values within the established regulations. Only few studies have focused on this field and additional experiments and case studies are necessary to uncover whether there is a problem. [392] discussed how both wet and dry methods can be applied to improve fly ash quality. The capability of the residual carbon to adsorb AEAs can be reduced by exposing fly ash to an oxidizing environment. content in fly ash lead to reduced air loss or decreased AEA requirements in freshly mixed concrete. The setting and hardening characteristics of mortars and the flexural and mechanical strengths of the solidified specimens were optimized with respect to the dosage of natural and metal-loaded solid wastes. the wide installation of improved combustion technologies in order to reduce NOx emissions has lead to generation of fly ashes containing residual carbon having a higher adsorption capacity of AEAs (per unit mass of carbon). which describes a method for improvement of fly ash quality by ozone treatment. The process can take place at ambient temperature. hardly any precipitations of surfactants occur. Fly ash produced from pulverized coal combustion is used in concrete as pozzolanic additive. it . it is possible to prepare mortars with metal-laden fly ash that have strength comparable to cement only. It has been shown that both the particle size and the surface chemistry of carbon have impact on AEA adsorption. [105]. but has been stated by others to be of minor importance [383]. which are important to enhance air entrainment in concrete. to obtain the needed air entrainment in fly ash concrete mixtures. in this case. fly ash from coal/petroleum coke co-firing has shown a low AEA adsorption capacity. the metal-laden adsorbent was immobilized into cement for ultimate disposal and no significant leaching was observed from the stabilized products. The proposed technology (utilization of industrial wastes for effluent treatment and then ultimate disposal of adsorbents laden with pollutants in cementitious materials by fixation) provides a two-fold aim of wastewater treatment and solid waste management. Combustion of other alternative fuels may also affect the fly ash quality. Thus. The coal fly ash. e. mixing procedure and handling. This could be beneficial in future design of combustion technologies. making the mineral-rich fraction suitable as concrete additive. The process was operated without additional fuel. However. Detailed characterization of available adsorption sites. on a long-term basis is necessary before a conclusive recommendation can be made on the use of this mortar for construction purposes. The interaction between AEAs and fly ash appears to be related to the residual carbon present in fly ash due to its capability to adsorb the AEAs in the concrete mixture. work should include optimization of combustion conditions in order to avoid soot formation and destroy or passivate formed soot in the furnace. hardening and mechanical properties of the final concrete block.5 wt% was treated in a fluidized bed combustor. further evaluation of the properties. but they argued that wet methods give rise to problems such as high drying costs and loss of pozzolanic activity of the treated ashes. and volume change of the metal-laden fly ash mortar. [394. Finally. The demand of renewable energy sources has increased the use of biomass in the production of heat and electricity. Further. and disposal costs. were loaded to saturation with Pb(II). There are still some unresolved issues within this field. It may include other interfering parameters such as formation of insoluble compounds. durability. Regulations for approval of fly ash as concrete additive are typically based on the carbon content determined by the LOI test. Various methods have been suggested for the safe disposal of metal-laden fly ash. indicated that for an extended curing time. [392] estimated that development of a commercial post-treatment process based on ozone appears to be profitable. It is noted.395]. Lightweight aggregate Use of fly ash as a by-product aggregate in the manufacture of lightweight construction products presents itself as a logical utilization process for a number of reasons. The fired bricks with high volume ratio of fly ash were of high compressive strength. cost effective. sintered fly ash lightweight aggregates will reduce the dead weight and material handling cost for multistoreyed constructions. one-third less than conventional clay-fired bricks [410]. with less decay being caused by salt crystallization in the pores. Lytag. The other ingredients are lime. Fly ash used as a soil stabilizer along roadway embankments has been a beneficial practice for a number of reasons. In the field of Architectural Heritage. Cicek and Tanriverdi [416] observed the positive effect of the addition of fly ash. The porosity of the brick depends directly on the mineralogical composition of the raw material and the firing temperature. fly ash may be in plentiful supply from nearby electric power generation facilities. Plastering over brick can be avoided. yielding an excellent product. porosity.421]. The use of fly ash brick provides a stronger. The effect of fly ash with high replacing ratio of clay on firing parameters and properties of bricks were investigated. Ease of availability combined with positive physical properties can make fly ash soil stabilization cost effective. In addition to brick products. The roofing tiles have the advantage of being both lighter than clay products and providing a class A fire-rating making them an excellent replacement for cedar shake roofing in high fire danger areas. which is 50–100 C higher than that of clay bricks. The advantage of these bricks over burnt clay bricks are: Lower requirement of mortar in construction. more durable construction that is better protected from efflorescence and salinity with meaningful savings in construction costs. The main advantage is the economic saving to the manufacturer. Many countries like the UK. such as Terlite. The reduced cost is especially noticeable when products such as bricks are considered. Fly ash bricks weigh. etc. The cost is reasonable compared to that of hallow brick and clay brick. low water absorption. edges. This is because fly ash causes a reduction in the number of micropores. The technologies are eco friendly. sinterlite. fly ash (20–50%) is used along with clay to produce clay bricks which are more porous (40– 50%) than fly ash bricks (20%). it has rarely been applied to bricks. Even though pulverised fly ash brick at first instance may appear to be costlier than conventional products. USA. bricks fired at high temperatures are more vitreous and undergo the greatest changes in size and porosity [417]. Ahmaruzzaman / Progress in Energy and Combustion Science 36 (2010) 327–363 appears that the fixation process can be environmentally safe. Shear strength is an important characteristic for soil stabilization fly ash utilization and it generally equals or exceeds the strength of soils typically used for embankments [420. There is good demand for fly ash bricks. Fly ash in wet state with low quality was also used as raw material to replace clay to make fired bricks [419]. Metal-laden fly ash should be considered for use in secondary construction materials. Additive can be chosen to improve the plasticity index of mixture to meet plastic extrusion used in most brick making factories. energyefficient and environment friendly (as avoids the use of fertile clay). on average. Controlled dimensions. as an aggregate filler. The properties of fired bricks were improved by using pulverized fly ash. because the main raw materials fly ash is generated by thermal power stations in a large quantity. the pores that make porous materials most vulnerable to salt-induced decay. The technical quality of compositionally different groups of solid bricks fired between 800 and 1000 C was evaluated [418].1 to 10 mm. Fly ash can be used in the range of 40–70%. smooth and fine finish and can be in different colours using pigments. gypsum (/cement). An essential criterion in this case is that the bricks must have the same physical and mechanical parameters (colour.M. subgrade base course material. Minimum compressive strength (28 days) of 70 kg/cm2 can easily be achieved and this can go up to 250 kg/cm2 (in autoclaved type). Recently it has been shown that fly ash might improve the compressive strength of bricks and make them more resistant to frost [415]. 13. sand. sand and hydrated lime in the compressive strength of the bricks. Fly ash has been used in embankment soil stabilization. and stone dust/chips. as compared to the non-light weight product when weight is a factor. except that the samples with the additive contained spherical fly ash particles with diameters ranging from 0. The textures of the bricks with fly ash were very similar to the textures of those without it. no frost and high resistance to frost-melting. Waylite corsonalite. It has found that fly ash bricks are as durable as clay bricks and in fact in certain aggressive environments perform better than clay bricks. The manufacture of sintered fly ash light weight aggregates is an appropriate step to utilize a large quantity of fly ash. Use of this additive could have practical implications as a means of recycling and for achieving cost savings in brick production. Being lighter in weight. Depending on the type of soil.) as the original bricks used in the building being restored. In the brick making industry. ultimate financial benefit can be evaluated in terms of its increased physical and chemical properties. no cracking due to lime. Road sub-base Utilization of fly ash as a material in the construction of roadways and associated peripheral projects has been a significant outlet for fly ash. but generally. Although fly ash is commonly used in cements. The second economic reason is an abundance of low-cost fly ash available to make the bricks. Fly ash supplied by thermal power stations at free of cost. The results indicate that the plasticity index of mixture of fly ash and clay decreased dramatically with increased replacing ratio of fly ash. In areas where borrow or fill and cover material are scarce. hydraulic properties. Fly ash bricks manufacturing units can be set up nearby thermal power stations. But the greater benefit lies in controlling two major 353 ecological problems of fly ash disposal and the reduction of cultivable land that is needed for the production of burnt clay brick. The awareness among the people is required and also same time the government has to give some special incentives for these types of activities. thus reducing shipping costs and improving profit margins. there is almost no research about fly ash addition in the manufacture of replacement bricks for use in restoration work. there has been research into how to reuse different waste products in order to manufacture better quality bricks [411–414]. fly ash has been utilized in the manufacture of lightweight roofing products such as rigid roofing tiles. enabling a truck to carry more bricks per load. Germany. the entrepreneur has to bear only transportations charges from thermal power stations to the fly ash bricks manufacturing unit. Though clay-fly ash bricks have high strength and absorb less water than fly ash bricks. Several studies show that fly ash brick is a far superior building material than burnt clay brick. etc. The sintering temperature of bricks with high replacing ratio of fly ash was about 1050 C. These particles led to a reduction in the density of the bricks and a substantial improvement in their durability. This strength is partially due to some fly ash having self-hardening or pozzolanic . associated with the reduced freight costs of shipping of the finished product. 14. a bituminous pavement additive and as a mineral filler for bituminous concrete. Poland and Russia are producing lightweight aggregates commercially under different trade names. reduces solid waste and dust in the nature. which is a characteristic more common to class C fly ash and ash from atmospheric fluidized bed boilers. considerable savings in construction cost can be achieved. more research into the chemical aspect and the interaction of the coal combustion byproducts. Since about 80% coal is produced from open cast mines.354 M. itself. When fly ash is used in concrete. Moisture from surrounding strata eventually provided the fly ash with the water needed for hydration and the fly ash hardened. Acid mine drainage occurs in areas that have previously been mined for coal and contain pyritic materials in spoil piles or in mine shafts. Since there is no seepage of rain water into the fly ash core. subsidence control and fire abatement are identical [422]. the actual savings achieved will be much higher and fly ash use will be justified even for lead distances up to say 100 km. let alone for underground disposal. Research and Development are still on for commercial use of such huge quantum of fly ash as mine-filling material. No degradation of groundwater was found following the injection at this project. The eventual filling at the roof covered 15 feet in either direction from the borehole and provided an airtight seal for the mine shaft. The spoil piles and mine shafts contain iron pyrite in the tailings that chemically react with oxygen. Even when it is used in stabilisation work. where the groundwater table intersects the mining rubble. The ash had an angle of repose of only 8 degrees from the horizontal exhibiting excellent ‘flow’ characteristics. the first being for the control of AMD. Also. Similarly. Experimental results determined that an ideal water content equating to approximately 100 gallons per ton of fly ash (25% water by total mix weight). laying and rolling cost are there in case of fly . the national Thermal Power Corporation Limited (NTPC). The procedures for conducting underground mine void filling with fly ash for AMD control. Since there are various limitations and threats to environmental degradation. exhibiting no signs of shrinkage or settling. mine water. dry fly ash injection or wet slurry injection. is facing problem of disposal of the abundant overburden wastes (w6000 million m3) as against their in situ volume of the available open cast mine pits (4000 million m3) and regaining the configuration of the landscape [424]. and groundwater is needed to assess the environmental impact of coal combustion by-product mine injection. the economy achieved is directly related to transportation cost of fly ash. resulting in acid mine drainage. Fly ash grout injection is currently being considered for use at a closed underground mining Site. even areas that have partially collapsed can be filled with fly ash grout material to prevent further subsidence. laying and rolling cost are there in case of fly ash. produces a slurry that pumps easily and does not shrink upon drying. surrounding the coal seams. Hence chances of pollution due to use of fly ash in road works are negligible. India used about 60.. Cost estimation Fly ash is available free of cost at the power plant and hence only transportation cost. During 1999–2000. The technical feasibility of disposing coal combustion by-products in underground mines has been proven and the selection of this disposal alternative will be decided based primarily on cost and regulatory compliance issues. If environmental degradation costs due to use of precious top soil and aggregates from borrow areas quarry sources and loss of fertile agricultural land due to ash deposition are considered. water and Thiobacllus bacteria. is in crucial stage of being able to handle this excessive overburden and planning for fly ash back filling in the abandoned mines for eco-engineering development with viable plant life.. Fly ash is available free of cost at the power plant and hence only transportation cost. Ahmaruzzaman / Progress in Energy and Combustion Science 36 (2010) 327–363 properties. The third use for fly ash injection is mine fire control. Environmental weathering over time caused the pillars to crumble and AMD to occur due to the exposure of the pyritic material. Mine backfill Mine back filling has demonstrated to be an attractive option for those plants located near the coal mine. when fly ash is used as a fill material. additional research on the technical issues of injecting coal combustion by-products or coal combustion by-product slurries should only be needed in limited special circumstances. a similar chemical reaction takes place which binds fly ash particles. by neutralizing AMD and by preventing contact between water and pyritic materials. Fly ash mine void filling has been carried out in both controlled circumstances and in actual field applications. involves encapsulation of fly ash in earthen core or with RCC facing panels. Fly ash-water slurry injection is conducted in much the same manner as dry ash injection with the exception of the use of higher injection pressures (up to 100 psi) and a slightly larger 10 inch borehole being drilled [422]. where the pyritic material is in contact with both water and atmospheric influences. 15. Two methods can be used. The second reason for fly ash grout injection compliments AMD control by filling mine voids and providing support to areas where standing coal pillars are crumbling and causing land subsidence on the surface. Southern India. Mine void filling is undertaken for numerous reasons. For example. 16. The dry fly ash easily flowed 65 feet in either direction from the borehole along the shaft as it filled to the mine roof. A pilot study of fixated scrubber sludge injection into an abandoned underground mine was recently performed by the Indianapolis Power and Light Company at their Petersburg Station.000 ton of ash for backfilling underground mines of Singareni Colliery Company Limited. These by-products are different both physically and chemically from fly ash and require additional research. If the lead distance is less. As such. The potential application of coal fly ash in reclaiming abandoned coal mine is of great practical significance. On the other hand. Coal India Ltd. Hence. many electric utilities have installed FGD scrubbers to meet the requirements of the 1990 Clean Air Act Amendments. Use of fly ash in road works results in reduction in construction cost by about 10–20%. while disposing of large quantities of fly ash at the same time. On the contrary Coal India Ltd. Through the use of high pressure injection. it chemically reacts with cement and reduces any leaching effect. leaving only small pillars to maintain the structural stability of the surrounding land surface. in collaboration with Central Mining Research Institute. the use of fly ash in pavement construction results in significant savings due to savings in cost of road aggregates. Bulk quantities of coal fly ash have been used to replace the conventionally used sand for reclaiming underground mines. Open cast mine filling can again be considered as land reclamation. The dry fly ash is then injected at relatively low pressure (12–30 psi) into the mine void. Underground coal mining operations conducted many years ago removed large volumes of coal. The injection process would reduce acid mine drainage (AMD) through a two-fold approach. Construction of road embankments using fly ash. to the groundwater and atmosphere. many new coal combustion by-products are being generated and are presenting challenges for surface disposal. effective scientific work is to be done before a firm decision is taken for bulk use of fly ash in reclaiming abandoned mines. Dry fly ash injection consists of drilling 6 inch diameter boreholes into the mine void and placing steel casing down to that level. leaching of heavy metals is also prevented. local geology. Back filling of underground mines is technically vulnerable and especially holds good potentials for those areas where sand is scarce. India[423]. to comply with environmental requirement. product demonstration and commercialization. Hence. serious efforts are to be made to tackle this alarming situation of fly ash management to reduce the adverse effect on environment and ecology and future hypothesis by finding remedial measures for the social development. This draft calls for the change of coal combustion products (CCPs) to coal combustion by-products (CCBs) to iterate the ideal definition of a product. the use of fly ash in pavement construction results in significant savings due to savings in cost of road aggregates. Therefore. which is the principal reason for a process. In order to evaluate the financial implications of fly ash utilization in road construction as an alternative. anything else is a by-product. It is argued that coal is burned to produce energy.M. Principal technical barriers include issues related to coal fly ash production. the finished product would cost approximately $15 ton1[94]. Ahmaruzzaman / Progress in Energy and Combustion Science 36 (2010) 327–363 ash. Recommendations were submitted to the committee for action in 2001. Further. used in the process. Hence. It is essential to follow best engineering practices to ensure that there is no environmental risk. energy is the product of coal-burning processes. If the lead distance is less. Technical and economic barriers are not mutually exclusive in that technological advancements usually result in economic feasibility. Barriers to utilization There are a number of technical. etc. economic. etc. Waste baggase fly ash is available for $2 ton1. There is a production of huge quantity of fly ash followed by emission of green house gases and intrude significantly for global warming. not ash. the actual savings achieved will be much higher and fly ash use will be justified even for lead distances up to say 100 km. was recently formed to address the question of standards and definitions of coal and coal combustion products (CCP)-related terms. Restriction of excavation of earth for filling low-lying areas and construction of embankment within 200 km radius of thermal power plant is essential. respectively. Future research and prospects Fly ash has a great potential in environmental applications and interesting alternative to replace activated carbon or zeolites for adsorption in the air or water pollution treatment. An American Society for Testing and Materials subcommittee under the Committee E-50 on Environmental Assessment. Typically cost of borrow soil varies from about Rs. materials characterization. stone chips. and through the potential for leachates containing trace elements from fly ash. and viewpoint of the industry that Environmental protection agency (EPA) regulations and procurement guidelines are too complicated and rigid rather than being general guidelines for use. These are being overcome by various means in the utilisation sectors. In addition. Lack of awareness on the advantages of fly ash based products among end-users is limiting new initiatives and market potential. considerable savings in construction cost can be achieved. other barriers to increased use of coal fly ash can be overcome. With proper economic incentives. comparative costs of conventional and fly ash based road construction for a given geometry are needed. laying and rolling cost are there in case of fly ash. are to be transported to the work site. The fly ash transportation cost would have some finite value depending upon the lead. when fly ash is used as a fill material. Geological Survey (USGS) is represented. policy makers and fly ash generators. The high cost of 355 transportation of low unit-value coal fly ash and competition from locally available natural materials pose two of the most important economic barriers. The effect of lead on construction cost savings reveals that the investment on fly ash based road construction would be financially attractive only for a lead less than 60 and 90 km for flexible and rigid pavements. The soil is locally available in abundance whereas other materials like stone aggregate. chemicals. The cost of fly ash based road construction depends mainly on the cost of various resources replaced by fly ash and lead (transportation distance). For coal-burning electric utilities.100–200 per cubic metre. scientists. Fly ash transportation cost for reclamation of abundant mine and road construction is a major constraint. architects and manufacturers for the production of superior quality of fly ash based products to meet the consumer acceptability and increased marketability. Fly ash is available free of cost at the power plant and hence only transportation cost. If environmental degradation costs due to use of precious top soil and aggregates from borrow areas quarry sources and loss of fertile agricultural land due to ash deposition are considered. 18. transport.. specifications and standards. in association with scientists. 17. and userrelated factors.S. awareness of the quality parameters and beneficial effects of fly ash based building materials and its utility should be made clear to the general public for mass consumption and effective utilisation of fly ash. the revenues from the sale of coal fly ash are often insignificant. the economy achieved is directly related to transportation cost of fly ash. compositional inconsistencies in the products. It can be seen that the cost savings in fly ash based embankment road construction is nearly 31% which is in close agreement with the range of 30–40% savings cited by construction agencies in India [426]. Cost benefit analysis of fly ash versus conventional building materials are needed to be thoroughly evaluated for the concrete recommendation for maximising the use of coal fly ash.. institutional. and legal barriers to the use of large quantities of coal fly ash. Subcommittee members evaluated the latest draft of the definitions document. and considering the cost of transport. Kumar and Patil [425] assumed that fly ash is available free of cost and in the form suitable for road construction. The loading/unloading cost of the conventional material and fly ash is also assumed to be the same. and engineers have formed a number of national and international organizations to address the removal of barriers to use of coal fly ash. It is also found that the maximum percentage savings in construction cost can be obtained in GSB layer due to complete replacement of the materials by fly ash. The construction cost of a given layer of fly ash based road formation is the sum of the two cost terms representing (i) conventional layer cost construction minus cost of resource savings due to fly ash utilization and (ii) transportation cost of fly ash. Also similar situations exist in many developed and developing countries. lack of State guidelines. Barriers to utilisation of coal fly ash on land occur in marketing. sporadic data on environmental and health effects. Concerned industry and government representatives. It was found that the total road construction cost savings percentage decreases with lead due to increase in the fly ash transportation cost. belief that other raw materials are readily available. on which the U. there should be a mandatory condition in the policy legislation to use fly ash in place of soil for such applications. electrical energy. Use of fly ash in road works results in reduction in construction cost by about 10–20%. the costs of fly ash based road construction with flexible and rigid pavement for different lead were calculated. Similarly. There should be an integrated approach by the coordination of technologists. Economic barriers to increased use of coal fly ash can be key among all factors affecting by-product use. Adsorption . Among the institutional and legal barriers are the lack of knowledge of potential ash uses. Based on cost data of different resources saved. such as. Ohio: Battelle Columbus Laboratories. More efforts should be attempted in this area. Zeolite has a variety of applications as adsorbents and ion exchangers and exhibits much higher capacity than the raw fly ash. vol. Fahmi R. There is a scarcity of information on the environmental impact of fly ash as an ingredient in the preparation of materials. 1981. [12] ASTM standard specification for coal fly ash and raw or calcined natural pozzolan for use in concrete (C618-05). CO 80014. Conclusion This paper has attempted to cover a wide spectrum of information so that the reader can better understand fly ash utilization. dyes. Lothia RP. Environmental geology notes 96. Gordon and Breach Science Publishers. Ahmaruzzaman / Progress in Energy and Combustion Science 36 (2010) 327–363 performance of fly ash strongly depends on its origin and chemical treatment used for activation. the use of fly ash as soil amendment has been studied. allowing the high volume use of ash from sources that do not meet ready-mix concrete specifications. There should be a greater emphasis on the development of new technology for efficient utilization of fly ash. Separation of unburned carbon from the minerals can bring benefits for applications of unburned carbon and utilization of mineral section for cement production and zeolite synthesis. Use of TMA to predict deposition behaviour of biomass fuels. The higher percentage of unburned carbon in fly ash will lead to efficiency loss and poor marketability for cement production. it is an important raw material for various applications. The unburned carbon in fly ash plays an important role for adsorption and converted to activated carbon. which will enhance the adsorption capacity. [3] Bhattacharjee U. Kikuchi R. IL: Illinois State Geological Survey. possibly through employing life cycle assessments (LCAs) is needed. Bridgewater AV. In: Annual book of ASTM standards. [7] Querol X. For maximum benefit.com/properties. American Society for Testing Materials. Dhanpat R. new technologies for the efficient utilization of fly ash should be made use. Columbus. separation of unburned carbon from fly ash will be beneficial to fly ash application. Alastuey A. farmers may use fly ash rather than lime to enrich their soil. 1982. and to increase mineral content in the soil. and FGD absorbent. References [1] Joshi RC. Resour Conserv Recycl 2001. and further development work is needed. vol. Unburned carbon is an important component of fly ash. 1997. Generally. 2. is a light weight building product with high insulating value. although posing environmental pollution. Sajwan KS. [2] Mukherjee AB. Power station fly ash – a review of value-added utilization outside of the construction industry. Int J Coal Geol 2002. . Modification of fly ash would enhance the adsorption capacity [179]. However. Few researchers have been succeeded in the conversion of the bulk fly ash into pure zeolite [7]. [5] Iyer RS. Unburned carbon is similar to the precursors for production of premium carbon materials. with carbon content up to 12% may be used. Fly ash contains aluminosilicates and a potential source for the synthesis of zeolites. Economic barriers have to be overcome in terms of high value and high volume utilization for the industrial applications of fly ash. Jones JM. [9] Roy WR. the full scale application of this technology has not been implemented. et al.27:151–66. Lesher CE. [15] Llorente MJF. Autoclaved cellular concrete (ACC). [11] Mattigod SV. Moreno N. unburned carbon contents generally range between 2% and 12%. Fly ash use for agriculture and land reclamation: a critical literature review and identification of additional research needs. Fly ash. Fuel 2006. Activated carbon made from unburned carbon of fly ash has a significant potential of cost advantage over other activated carbon. Jenkins BM. Fly ash can be used for the synthesis of geopolymers [427. Resour Conserv Recycl 1999. USA: American Coal Ash Association. Some investigations have been made in the hydrothermal conversion of fly ash into different types of zeolites using the extracted supernatant solution.htm. Fuel 2007. Resour Conserv Recycl 2008. High temperature elemental losses and mineralogical changes in common biomass ashes. 17–19. Lopez-Soler A. Therefore. Fly ash can be considered as a valuable resource and needs to be studied. In: Advances in concrete technology. In fly ash. removal of organic compounds. Garcia JEC. Coal fly ash: a review of the literature and proposed classification system with emphasis on environmental impacts. Energy 2002.85:1273–9. The utilization of fly ash in construction. In: Ash at work. raw fly ash has low adsorption capacity. Hernandez E. Williams PT. [13] Thy P. more research should be conducted in these areas. Mercury flow via coal and coal utilization by-products: a global perspective. [4] Burke M. Suloway JJ. The presence of silico-aluminate phases in fly ash makes it a suitable raw material for the synthesis of geopolymer.02. Up to date. Arthur MF. Kandpal TC. vol. Journal of Environmental Quality 1990.52(4):571–91. Grundvig S.428]. in most cases. and those derived from more ‘traditional’ routes has not been extensively tackled. Thiery RG. mullite and quartz–cristobalite–tridymite. Fuel 2006. heavy metals. Geochemical factors controlling the mobilization of inorganic constituents from fossil fuel combustion residues: I. Concentration of elements in woody and herbaceous biomass as a function of the dry ashing temperature. such as. Fly ash utilization programme must be extensively taken up covering various aspects at different level to minimize the environmental pollution. the synthesis of ultramarine blue. 19. Eary LE.31:217–28. et al. [16] Bridgeman TG. Shiraki R. Schuller RM. no industrial scale application has been realized. chemical modifications of fly ash is needed.27:333–46.85:783–95. CCP experts gather in India. Acknowledgement The author would like to thank the reviewers of this manuscript for their valuable suggestions and comments.19:188–201. Fuel 2007. Buhre BJP. 2. More analysis of long-term economic and environmental impacts. concrete and aggregates. activated carbon. either for carbon recycling or mineral fly ash application in cement production and zeolite synthesis. RP-1224-5. in order to facilitate the application of fly ash to new and innovative areas of economic interest. Potential of fly utilization in India. Synthesis of zeolites from coal fly ash: an overview. [6] Kikuchi R. The amorphous aluminosiliate nature of fly ash makes it a possible raw material for many industrial reactions. Champaign.86:60–72. properties and uses. Darvell LI. 04. Fly ash in concrete: production. Repeated harvesting of foodstuffs depletes trace elements in the soil. reported work to date in this area has been of laboratory scale.86:2446–56. Fly ash. Application of coal ash to environmental improvement – transformation into zeolite. Ainsworth CC. Zevenhoven R. Although. few investigations have been currently conducted in the utilization of unburned carbon for production of activated carbon. [8] http://flyashindia. thereby. potassium fertilizer. The trace elements in fly ash might be used to replace trace elements in the soil.356 M.50:413–23. Wall TF. [14] Masia AAT. The review pointed out that the key issue of critical comparison between fly ash generated products and processes. whose composition in fly ash varies with combustion efficiency. which can be manufactured using 60–75% fly ash by weight. Review of the major elements. Bhattacharya P. Further research in this area is needed. and zeolite synthesis can help a great deal in the reduction of environmental pollution. Pomeroy SE. To improve removal efficiencies and adsorption capacities. 2007. Scott JA. Understanding coal formation and combustion processes provides both a background and basis for the alternative uses of the resultant fly ash. Therefore. [10] Tolle DA. 2005. In future. Gupta RP. This review aimed to act as a stepping-stone for the prospective researchers into the rewarding field of fly ash. Umana JC. This review has shown that. Studies on separation characteristics of hexavalent chromium from aqueous solution by fly ash. Naiya TK. Parwate AV. [30] Maroto-Valer MM. EPA-452/R-97–10. Unburned carbons from fly ash for mercury adsorption II: adsorption isotherms and mechanisms. Day RL. Joshi MV. J Chem Technol Biotechnol 1984. Eidson AF. J Jpn Soc Atmos Environ 2000. Narayanaswamy MS. Olson ES. Martı´nez L. Relationship between the textural properties. [77] Kapoor A. Gehrke M. Bhadra AK. with emphasis on mercury content. Fly ash for the treatment of Cd (II) rich effluents. Singh VN. Investigation of flue gas desulphurization by fly ash and calcium hydroxide mixtures. Waste Manage 2002. [20] Yu Q. Resour Conserv Recycl 1983. Taulbee DN. Energy Fuel 2007. Removal of Cr(VI) from aqueous solutions by adsorption on fly ash-wollastonite. J Hazard Mater 2002. Energy Fuel 2007. Equilibrium studies for the sorption of zinc and copper from aqueous solutions using sugar beat pulp and fly ash. Yeh CM. Adsorption of mercury (II) by coal fly ash. Energy Fuel 2003.148:538–47. [34] Skillings Mining Review.1: 36–9.77:1212–8.46:927–31. Fuel 1996.3898:1–16. Cetin S. Status review of mercury control options for coal-fired power plants. In: Proceedings of the national conference on complete wateruse. Mayoral MC.95:251–73. Low coat FGD systems for emerging markets. J Chem Technol Biotechnol 2002. Sanderson MA. Rudimentary. [83] Bayat B. Chem Eng J 2006. Tutem E. Energy Fuel 2001. 24–27 August 1993. Martı´nez-Tarazona MR. IEA Coal Research IEAPER/19.8:225–34. Removal of hexavalent chromium by adsorption on flayash. Adsorpt Sci Technol 1992. Sugita S. Hower JC.1(M-319):30–40. [60] Dasmahapatra GP. Das SK. [81] Banerjee SS. J Inst Eng (India). Effect of fly ash characteristics on the removal of Cu(II) from aqueous solution. Martı´nez-Tarazona MR. Sua´rez-Ruiz I. Selective adsorption of heavy metal cations by using fly ash. Andrews R.9:130–47. Leahy JJ.19:869–73. Effects of biomass co-firing with coal on ash properties. Mercury emissions and effects – the role of coal. Retention of elemental mercury in fly ashes in different atmospheres. [54] Rovatti M. [29] Lu GQ. Shoya M.34A:367–74. Fuel 2004.M. Fuel 2008.21:1915–23. Mercury Study Report to Congress. Isojima Y. Adsorption of lead and mercury by rice husk ash. Mandal SN. [39] Lo´pez-Anto´n MA. Part 1: characterisation and PSD.86:853–7. 357 [51] Hall B. Chemosphere 1995. [41] Li Z.136:69–92. [36] Sakulpitaphon T. [35] Pavlish JH. O’Callaghan MN. Dı´az-Somoano M. Hower JC.83:223–30. [37] Hower JC. Taulbee DN. [28] Klingspor J. Kanda O. Hwang JY. Comparative study of adsorption properties of Turkish fly ashes. Rovatti M. The case of nickel(II).22:821–30. [46] Baltrus JP.31:2001–9. Hasatani M. Operation results of the first commercial dry desulfurization plant in Hokkaido Electric Power Co. Fuel 2001. Viraraghavan T. copper(II) and zinc(II).1:137–43.39:697–704. Takeshi F. Wells AW.19:209–27.21:885–8. Scurlock JMO.32:430–40. [21] Naik BR. Adsorption of Cu2þ from water using raw and modified coal fly ashes. Laudal DL. [64] Bayat B. International ash utilization symposium. Garcia P. Bioresour Technol 1996. 8A and 8B. Do DD. J Hazard Mater 2002. J Hazard Mater 2007. Thomas GA. Fuel Process Technol 1991. Water Res 1998. Comparative study of adsorption properties of Turkish fly ashes. 13):9. Fuel 2007. Deutch S.25:930–5. J Colloid Interface Sci 2004. Singh VN. Diehl JR. Copper and cadmium adsorption on pellets made from fired coal fly ash. Dı´az-Somoano M. Removal of nickel(II) and zinc(II) from wastewater using fly ash and impregnated fly ash. Izquierdo MT.15:193–201. Rodriguez P. Copper(II) removal from aqueous solutions by fly ash. . [47] Kulaots I. Joshi MV. Lin Q. Chemosphere 2001. Heavy metal cation retention by unconventional sorbents (red muds and fly ashes). Peloso A. Size distribution of unburned carbon in coal fly ash and its implications. Fuel 2005. Sugita S.80:795–800. [70] Papandreou A. Sawayama S. [80] Ayala J. Penn State researchers study use of coal by-products. [22] Grammelis P. Middendorf B. White CM. Use of unburned carbon in fly ash as precursor for the development of activated carbons. Adsorption of Zn(II) from aqueous solution by using different adsorbents. Adsorption properties of fly ash particles for NOx removal from flue gases. 3. Mercury capture by distinct fly ash carbon forms. Abad-Valle P. [23] Ngashima N. Miscanthus: European experience with a novel energy crop. I.123:43–51. Martı´nezTarazona MR. Trimble AS. Energy Fuel 1999. Bona MT. II. J Hazard Mater 2006. Mann MD. Jayaram RV. Sakulpitakpton T. May 4–8. Dı´az-Somoano M.1:79– 96. Gong F. Hower JC. [61] Panday KK.143:561–6. Hugul M. 1995. Yu CC.21:59–70. Characterization of carbon concentrates from coal-combustion fly ash. Prasad G. Roque P.30:611–27. Fauth DJ. Characterization of differing forms of unburned carbon present in fly ash separated by density gradient centrifugation. Gonzalez R. Hower JC. De AK. Sep Purif Technol 2008.88(7):1194–200. Arsenic and mercury partitioning in fly ash at a Kentucky power plant.38:1015–32. Hizal J.84:911–6. [19] Martirena F. Panias D. Vasilikiotis G. [82] Banerjee SS. Arashi N. Jayaram RV.40:1973–9. Novel separation of the differing forms of unburned carbon present in fly ash using density gradient centrifugation. Tade MO.87:1355–9. [55] Rotenberg SJ. The reaction between rice husk ash and Ca(OH)2 solution and the nature of its product. p. Hurt RH. [66] Yadava KP. Agblevor FA. Newton GJ.278:1–8. The influence of carbon particle type in fly ashes on mercury adsorption. Ahmaruzzaman / Progress in Energy and Combustion Science 36 (2010) 327–363 [17] Wiselogel AE. Thodos G. Sep Sci Technol 1996. The case of chromium(VI) and cadmium(II). Biomass Bioenerg 2000. Adsorption of Hg and NOx on coal by-products. Kakaras E. 39. fly ash carbons and Hg capture in fly ashes derived from the combustion of anthracitic pulverized feed blends. Energy Fuel 2000.75:713–6. Alexiades C. Investigation of the SO2 adsorption properties of Ca(OH)2-fly ash systems. 1975.44:1185–92. [42] Sua´rez-Ruiz I. Leahy MJ. Skillings Mining Review March 27 1999. 1993. Weesmaa J. The use of fly ash from the combustion of poultry litter for the adsorption of chromium(III) from aqueous solution. 1999. Austrian fly ash as a heavy metals removal material. [59] Grover M. [84] Bayat B. J Hazard Mater 2002. O’Dwyer TF.82:89–165. Ind Eng Chem Res 2007. Poliner J. Anderson C. Mercury retention by fly ashes from coal combustion: influence of the unburned coal content. Removal of heavy metal ions from aqueous solutions with fly ash. Istanbul. Boston: Electric Research Institute. [38] Hower JC. [43] Sua´rez-Ruiz I. [45] Maroto-Valer MM.29:37–43. Thomas GA.3897:1–23. Resour Conserv Recycl 1988. Clifton-Brown JC. [25] Davini P. Resour Conserv Recycl 1995. Environ Sci Technol 1991. Blanco F. Characteristics of coal combustion products (CCP’s) from Kentucky power plants. p. Tyagi BS. Ferraiolo G. Bechtold WE.13:947–53. [32] Rubio B.10:211–20.85:2310–5. [40] Sloss LL. Mardon S. Concr Int 2003. In: SO2 control symposium. The case of nickel(II). Water Res 1985. [48] Lo´pez-Anto´n MA. Das SK. Energy Fuel 2007. [75] Wang S. Bhole AG.95: 275–90. Comparative reactivity of treated FBC.39:1611–29. [65] Kelleher BP. Taulbee DN. Terdkiatburana T. Flue gas treatment by activated carbon obtained from oil-fired fly ash. Turkey. J Hazard Mater 2002. J HazardMater 2007. Comparative study of adsorption properties of Turkish fly ashes.77:1147–54.17:1028–33. Single and co-adsorption of heavy metals and humic acid on fly ash. Fennell JA. Adsorption kinetics of vapor-phase m-xylene on coal fly ash. Fuel 2006. Fuel Process Technol 2003. Fuel 1998. Bhattacharya B. Thomas GA. Sondreal EA. Adsorption. [49] Lo´pez-Anto´n MA. Prasad G. [68] Panday KK. Combined removal of zinc (II) and cadmium (II) from aqueous solutions by adsorption onto high-calcium Turkish fly ash. [71] Pehlivan E.35:51–62. J Phys Chem 1965. [74] Hsu TC. 1997. Galbreath KICK. Mandal SN. J Min Mater Cgara Eng 2002.84:1338–50.137(3):529–41. Parra JB.36:1056–61. I. [50] Dubini MM. low tech incinerators as a means to produce reactive pozzolan out of sugar cane straw. Susceptibility to regeneration of fly ash as an adsorbent material. Luo X. Removal of Cr6þ and Ni2þ from aqueous solution using bagasse and fly ash. Schager P. Huisman W. Water Air Soil Pollut 2002.56:103–9.58:353–8. Removal of Cr(VI) and Hg(II) from aqueous solutions using fly ash and impregnated fly ash. [18] Lewandowski I. 1985. [58] Gangoli N. Pal TK. Suuberg EM. [69] Lin CJ. Singh VN. [24] Al-Shawabkeh A. [31] Rubel A.15:455–62. Panday KK. Kraus RN. Skodras G. [63] Bhattacharya AK. [33] EPA. [56] Comparative study of adsorption properties of Turkish fly ashes. copper(II) and zinc(II).135:193–9. [72] Alinnor IJ. Compositional changes during storage of large round switchgrass bales. Stournaras CJ. Johnson DK. Robl TL. Fuel 2008. Markey DC. Fly ash as adsorbent material for toluene vapours. Nobuo T. II. [27] Davini P. kinetics and equilibrium studies on removal of Cr(VI) from aqueous solutions using different low-cost adsorbents. Hg and Se capture and fly ash carbons from combustion of complex pulverized feed blends mainly of anthracitic coal rank in Spanish power plants. [44] Maroto-Valer MM. et al. Matsuda H.27:95–107. Mettzler G. Water Res 1987. 270–275. vol. Hower JC. [62] Bhattacharya AK. Sakulpitakphon T. Cem Concr Res 2006. Cem Concr Res 1999. In: Proceedings of the first international symposium on environmental technology for developing countries. Experimental studies on the removal mechanism of mercury vapor by synthetic fly ash.25:55–62. [67] Rao M.73:678–85. Fuel 2005. paper #19. Andres JM. Maroto-Valer MM. [26] Davini P. Tokerud A. Shoya M. Unburnt carbon from coal fly ashes as a precursor of activated carbon for nitric oxide removal. Sessions 7. The case of chromium (VI) and cadmium (II). Chang JE. Robl T. Adsorption of heavy metal ions from aqueous solution by fly ash. The homogeneous gas phase reaction of mercury with oxygen. Adsorption of mercury from wastewater by fly ash. and the corresponding heterogeneous reactions in the presence of activated carbon and fly ash.21:99–103. [76] Sen AK. Ferraiolo G. Sancho J. Groppo J.and PCC-fly ash for SO2 removal. [73] Feng Q. [53] Peloso A. Ahman S. [57] Bayat B. Yanik BH. Chem Eng J 2008. Taulbee DN. Schram WH. [79] Apak R. Sep Sci Technol 2003. Environ Technol Lett 1987. [78] Papachristou E. Part EN: Environ Eng Div 1982. [52] Masaki T. Can J Chem Eng 1995.14:224–6. Carbon 2002. Andersen JM. Schobert HH.88(No. ABB Review 1998. Sep Sci Technol 2004. 266:28–32.41:243–9.13:527–36. Mohan D. Kinetics and mechanism of phenol adsorption on fly ash. J Nucl Sci Technol 1996. Adsorption of zinc from aqueous solutions by fly ash. Water Res 2001. [141] Aksu Z. [133] Piekos R. Modelling individual and competitive adsorption of cadmium(II) and zinc(II) metal ions from aqueous solution onto bagasse fly ash. Akay G. Mishra IM. Adsorpt Sci Technol 1998. Saini VK. J Environ Eng 1994. Resour Conserv Recycl 2003. Experimental design methodology applied to adsorption of metallic ions onto fly ash. Colloids Surf A: Physicochem Eng Aspects 2004. Adsorption of phenol from wastewater by peat. Uptake of inorganic orthophosphate by Greek fly ashes characterized using various techniques. Acharya PK. Huang CP. Mohan D.32:1889–97.358 M. Basu JK. [120] Tsitouridou R. Modeling the adsorption kinetics of some priority organic pollutants in water from diffusion and activation energy parameters.34:55–68. Removal of phenol from aqueous solution by adsorption on to coal fly ash. [101] Prabhu PVSS. Keskinler B. Adsorption of phenolic compounds on fly ash. [86] Srivastava VC. Phosphate immobilization from aqueous solution by fly ashes in relation to their composition. Wu D. coalcombustion. [145] Gupta VK. [117] Yildiz E. Das Gupta S. Sorptive removal of cesium-137 and strontium-90 from water by unconventional sorbents. [92] Gupta VK.8:46–52. Jimenez MC. [103] Mathur A. J Chem Technol Biotechnol 1987.16:273–83. Mondal K. As(V) removal from aqueous solutions by fly ash. [140] Aksu Z. Lecuyer I. Application of fly ashes in the removal of metal ions from wastewater. Narayanaswamy MS.33:396–402. Defluoridation of water by adsorption of fly ash. [119] Johansson L. Removal of heavy metals from main sewer-water of Varanasi city by adsorption on fly ash and blast furnice slag.71:180–6. [98] Pan SC.57:59–70. .34:259–65. Hequet V. [109] Pattanayak J. Lecuyer I. Paslawska S. p. J Hazard Mater 2005. re-integration). de Maria Alfaro F. Sorption of phosphate from solid/liquid interface by fly ash. Kadu PA.82:153–9. [107] Diamadopoulos E. Yadav IS. Upadhya YD.280:322–33. Utilisation of bagasse fly ash (a sugar industry waste) for the removal of copper and zinc from wastewater. Removal of 2.77:382–8. J Chem Technol Biotechnol 1998. [111] Allen SJ.42:6619–24. J Hazard Mater 2000. [130] Reardon EJ. Pathak KICK. Removal of 2. Hoxha EM. Toxicol Environ Chem 1988. Removal of divalent heavy metal mixtures from water by Saccharomyces Cerevisiae using crossflow microfiltration. Gal M. Tseng DH. J Hazard Mater 1998.41:185–7. Larrubia MA. [127] Bayhan YK. Çakici A.271:321–8. [89] Rio S. A comparative adsorption/biosorption study of mono-chlorinated phenols onto various sorbents. Huang CP. J Hazard Mater 2000. Water Res 1980. [105] Weng CH. Tutem E. [152] Singh AK. Experimental and numerical modeling studies of arsenic removal with wood ash from aqueous streams.74:546–53.B139:293–300. J Chem Eng Data 1996. Removal of cadmium(II) and zinc(II) metal ions from binary aqueous solution by rice husk ash. Yadav IS. Pekdemir T.4-dinitrophenol using bagasse fly ash. [114] Kuziemska I. Wang YX.2:333–6. [150] Singh BK. Ali I. Environmentalist 1999. [148] Viraraghavan T.35:241–52. [95] Gupta VK. Removal of phenols by adsorption on fly ash.37:4038–44. Water Air Soil Pollut 1993. [93] Gupta VK. 4 dichlorophenol. Ali I. [108] Rahman MH. Colloids Surf A: Physicochem Eng Aspects 2008. Phosphate removal using blast furnace slags and opoka-mechanisms. Reusing sewage sludge ash as adsorbent for copper removal from wastewater. Removal of cresol from aqueous solution using fly ash as adsorbent: experiments and modeling. Ind J Chemical Tech 1995. Delebarre A.49:51–61. [142] Daifullah AEH. J Colloid Interf Sci 2003. Ahmeti XM. [100] Rao M. In: 1999 Congress (recovery. [94] Gupta VK. [91] Gupta G. [126] Chen J. IPPTA: Q J Indian Pulp Paper Tech Assoc 2001. Sun Z. Sharma S. Usage of coal fly ash. high calcium. Bhattacharya B. Lycourghiotis A. [87] Ricou P. J Environ Qual 1988. [96] Gupta VK. Water Res 2001. Sep Purif Technol 2004.35(9):2191–200. Chaudhuri SK. [116] Ugurlu A. Sharma S. Kavak D. Guclu.73:471–80.2:311–7. Singh VN. Park KT.34:1777–96. Adsorption isotherm models for basic dye adsorption by peat in single and binary component system. The usage of dried activated sludge and fly ash wastes in phenol biosorption/adsorption: comparison with granular activated carbon. [99] Lin CJ. Mathew S. 1990. Removal of chlorophenols from aqueous solution by fly ash. Phosphate removal from water by fly ash using cross flow microfiltration. Removal of cadmium and nickel from wastewater using bagasse fly ash – a sugar industry waste. Torres N. Parwate AV. J Environ Sci Health Part A. Removal of zinc from aqueous solutions using bagasse fly ash – a low cost adsorbent. Sorption equilibrium studies of toxic nitro-substituted phenols on fly ash. Sakellaropoulos GP. Chen X. Gustafsson JP.33:1331–3.5:52–7. fly ash and bentonite. Loannidis S. [97] Gupta VK. In: Proceedings of the 1990 ASCE environmental engineering specialty conference. Adsorption of boron from aqueous solutions using fly ash: batch and column studies. Water Air Soil Pollut 1990. Environ Sci Eng 1999. Detoxification of bleach plant effluent using low cost adsorbents: removal of 2. [102] Gashi ST. [147] Kao PC. J Chem Technol Biotechnol 2002. Sep Purif Technol 2004.39:239–47. Contribution to the study of phosphate sorption by three Greek fly ashes. Delebarre A. [121] Vordonis L. ordinary Portland cement and related blends. Ind Eng Chem Res 2003.32:14–9. Koutsoukos PG. [132] Nemade PD. [113] Batabyal D. Removal of lead and chromium from wastewater using bagasse fly ash – a sugar industry waste. [138] Alemany LJ. 923–4. Srivastava SK. Cem Concr Res 2002. Le Cloirec P. Lin CC. Gad H. Huang TL. February 1999. Colloids Surf A 2005. Sep Sci Technol 2006. Yadava KP. Rao AV. [128] Yildiz E. Deborah EL. Sep Purif Technol 2000. Schwab AP. [90] Rio S. [131] Chaturvedi AK. IAWPC Technical Annual 1981. Treatment of metal industrial wastewater by fly ash and cement fixation. Huang CP. Waste Manage 2001. Narasa Raju TSS. Zhang D.4. Upadhyay SN. Environ Sci Technol 2000. J Indus Pollut Contr (India) 1989. Sep Sci Technol 1998. Georgiou J. Zn2þ and Pb2þ by adsorption onto fly ash and fly ash/lime mixing. Surfactant-enhanced crossflow filtration in nitrate removal from water.262:113–7. Removal of trace heavy metals by adsorption on fly ash. Guimaraes MS.38:589–96. [122] Cheung KICK. A parametric evaluation of the removal of As(V) and As(III) by carbon-based adsorbents. [104] Weng CH. Boron release and sorption by fly ash as affected by pH and particle size. Mall ID. Improving phosphate removal of sand infiltration system using alkaline fly ash. Phosphorus-fixing ability of high pH. Blasco JM. Use of fly ash in reducing toxicity of and heavy metals in wastewater effluent. 1988. Mall ID.17:129–38. Ind J Environ Health 1977. [118] Agyei NM. Kinetics and mechanism of removal of 2.a sugar industry waste material. Yener J. Lu MC. Water Res 1993. Removal of mercury in aqueous solution by fluidized bed plant fly ash. [136] Khanna SK. waste materials. Selimi TJ. [106] Weng CH. Khare SK. [146] Dutta B. Le Cloirec P. Zardkoohi M. Water Res 2000. Le Cloirec P. Valencia R. Wasiuddin NM.35:965–76. Water Res 2003. Gupta VK. Amsterdam: Elsevier Publishers.4(9):550–7. Can J Chem Eng 2004. Rawatn NS. Removal of heavy metals from industrial wastewaters. Keren R. Fresenius Environ Bull 1995. Sep Technol 1995. Water Sci Technol: Water Supply 2002. Phosphate immobilization using an acidic type F fly ash.82:968–77. Mishra IM. Sharma S. [124] Grubb DG.27:1773–7. [135] Ozturk N.52:49–58. Salman B. Application of water extract of brown coal fly ash to phosphate precipitation from polluted waters. Atun K. Removal of chromium (VI) from electroplating industry wastewater using bagasse fly ash – a sugar industry waste material.76:217–36. Sharma M.38:1345–60. J Hazard Mater 1998.4dimethyl phenol from aqueous solutions with coal fly ash. Delgado F. Ali I. J Hazard Mater 2007. Levent M. [134] Hollis JF. Potgieter JH. Adsorption characteristics of Zn(II) from dilute aqueous solution by fly ash.6-trinitrophenol using bagasse fly ash: a sugar industry waste material. [139] Akgerman A. Bhole AG. Sharma S.37:281–90. Environ Int 1998.14:1289–93. Adsorption Sci Technol 2004. The removal of phosphate ions from aqueous solution by fly ash. Arlington: VA.19:224–37. Mohan D. Phosphorus removal by fly ash.36:1–7. Carbon 2000. A limestone reactor for fluoride removal from wastewaters. J Water Supply: Res Technol-AQUA 2003.21:695–702. Cem Concr Res 2000.41:2685. Phosphate removal from water by fly ash using crossflow microfiltration. Metallic ion removal from aqueous solutions by fly ashes: multicomponent studies. [151] Singh BK. Nayak PS.247: 137–43. Singh D. Porter JF. Strydom CA. [112] Ravi AV. Performance of low-cost adsorbents for the removal of copper and lead. Fuel 2003. Akay G. Alappat BJ. Cakici A. Mall ID. [125] Agyei NM. slag. Ind J Environ Health 1994. A quantitative assessment of heterogeneity for surfaceimmobilized proteins. [115] Gray CA. [143] Gupta VK. Chemistry for protection of the environment 1987. [88] Ricou-Hoeffer P. Fluoride 1999.57:243–8. Sorption of semi-volatile organic compounds by bottom and fly ashes using HPLC. Mohan D. Removal of lead from wastewater using bagasse fly ash – a sugar industry waste material.35:241–52. [149] Sarkar M. [123] Oguz E.76:237–49. Mohan D. Sep Sci Technol 2003. Ruoainwar DC.17:181–4. Sahu A. Investigation of phosphate ion adsorption from aqueous solution by fly ash and slag. [110] Apak G. Kong H. Mishra IM. II. Colloids Surf 1988.22:295–309. J Colloid Interface Sci 2004.34:3247–53. Jain CK. Chem Eng Res Des 1996.312:172–84. Tzeng JH. Malhotra P.120:1470–87. Removal of fluorides from water using low cost adsorbents. Islam MR. Sorption characteristics of phenols on fly ash and impregnated fly ash. Blondin J. Chang JE. Tzannini A. [129] Yildiz E. Fluoride uptake characteristics of fly ash. Mckay G. Removal of Cu2þ. [144] Srivastava SK. recycling. Chemosphere 2000. Water Sci Technol 1999. Lalvani SB. Misran NM. Venkitachalam TH. Adsorption Sci Technol 1996. Ahmaruzzaman / Progress in Energy and Combustion Science 36 (2010) 327–363 [85] Srivastava VC. [137] Kumar S. J Colloid Interface Sci 2004. Johri N.69:309–20.24:911–8. Yener J.5:179–86.13:11–7. Daci NM.30:823–6.39:79–90.18:131–40.127:81–8. Strydom CA.19:129–36. Keskinler B. Anal Chem 2001. Utilization of bagasse fly ash generated in the sugar industry for the removal and recovery of phenol and p-nitrophenol from wastewater. [200] Mane VS. Ali I. Desalination 2007. Kobya M. Adsorption of basic dye from aqueous solution onto fly ash. Gates WE.44(10):3655–64. Geoffrey NK.36:189–96.73:269–78. Jain CK. Saini VK. Krishnan L. Agarwal NK. Al-Makhadmeh L. [190] Gupta VK. Water Res 1997. Adsorptive removal of auramine-O: kinetic and equilibrium study. [178] Kara S. Can J Civ Eng. Lafayette: Purdue University. The removal of dye colours from aqueous solutions by adsorption on low-cost materials. Viraraghavan T.143:226–32.292:336–43.39:129–38. [216] Annadurai G.38:4012–8. Misra AK. Removal of dyes from wastewater using bottom ash. Chemosphere 2003. Mishra IM. Mishra IM. Acar FN. Zhu Z. Int J Miner Process 2006. Water Res 2005. Adsorption kinetics and column operations for the removal and recovery of malachite green from wastewater using bottom ash. Prague: Institute of Chemical Technology. Water Environ Res 1997. 359 [187] Wang SB. Mathur RP. Adsorption of some organic acids on fly ash impregnated with hydroxides of Al. Yenisoy-Karakas S. Zhan SL. [206] Chaudhuri SK. In: Proceedings of 43rd industrial waste conference. Adsorption of phenols from wastewater. Removal of chrome dye from aqueous solutions by fly ash. Qian XQ. Swamy MM. [202] Viraraghavan T. Gurses A. Porter JF. Application of Langmuir isotherm for oxalic adsorption by fly ash and activated carbon. Brilliant Blue FCF. [197] Mall ID. Centre for Applied Energy Research. Dyes Pig 2006. 4-dinitrophenol from wastewater by adsorption technology: a batch and column study. Cengeloglu Y. [192] Gupta GS. Maleki A. Singh VN. fly ash and coal. Sinah VN. [170] Baneriee K. [181] Lin JX.34:505–17. Cheremisinoff PN.126:583–94. J Hazard Mater 2002. Agarwal M. J Colloid Interf Sci 2006. Sheih MS. [165] Banerjee K. Mittal J. Pakulanon K. Ng E. 1958. J Environ Monit 2002. Ali I.281:15–22. [199] Khare SK. [180] Wang S. [154] Mahvi AH. Removal of phenolic and lignin compounds from bleached kraft mill effluent by fly ash and sepiolite. [203] Ramakrishna KR. Fang MH.35:33–40. Removal of PCBs from wastewater using fly ash. Demirbas E. Sep Sci Technol 2000. Roels M. West Lafayette: Purdue University. Haraguchi K. Choueib A. Wu HW. Aydiner C. Cheng SL. Prasad B. Karunanithi T. Polat M. Water Res 1990. Sur B. Van Gerven Tom. Water Air Soil Pollut 1988. Prasad GR. Capacity and mechanism of phenol adsorption on lignite.37:4938–44. Adsorptive removal of malachite green dye from aqueous solution by bagasse fly ash and activated carbon-kinetic study and equilibrium isotherm analyses. [177] Dizge N. [Rev can ge´nie civ] 2006. Kumar K. Removal of 2. Adsorption 2005. Agarwal NK.69:210–23. Zhang DK. Srivastava RM. Khanna P. J Environ Manage 2008. . Adsorption of reactive dyes from aqueous solutions by fly ash: kinetic and equilibrium studies. Unburned carbon as a low-cost adsorbent for treatment of methylene blue-containing wastewater. Adsorption thermodynamics of carbofuran of fly ash. 397–406. Saxena SK. 2005. Detoxification using low cost adsorbents – removal of tetrachlorocatechol. The adsorption kinetics of ABS on fly ash. Fe and Ni. Saini VK.39:193–202. Adsorption of chrysoidine R by using fly ash in batch process. Adsorption treatment and recovery of the hazardous dye. Srivastava VC.61:492–501. Eye JD. Effects of cationic and anionic surfactants on the adsorption of toluidine blue onto fly ash. [211] Isam S. Mittal J. Sharma M. Prasad G.27:104–20. [194] Gupta VK.35:2097–113. Cd. J Environ Eng 2000. Water Res 2002. Adsorption kinetics of o-xylene by flyash. Agarwal S. kinetics andd thermodynamics.21:381–7. Al-Asheh S. Rachel MN. [167] Bhargava R. [176] Eren Z. Application of dried sewage sludge as phenol biosorbent. a sugar industry waste. Environ Sci Technol 2004.19:154–6.31:249–61. Microporous Mesoporous Mater 2003. Int J Environ Stud 1983. Ali I. Horng PY. 247. [198] Mall ID. Resour Conserv Recycl 1992. Removal of phenol from aqueous phase by using neutralized red mud. Singh KP. Panday KK. Ind Eng Chem Res 2006. Removal of chlorophenols from wastewater using red mud: an aluminum industry waste. The treatment of wastewaters containing TNT by sprinkling on ashes.4:978–84. Lee DJ. J Hazard Mater 2005.15:498–503. Singh VN.145:154–61. J Hazard Mater 2005.300:52–9. Srivastava VC. [205] Janos P.143:386–95. [183] Talman RY.60:1401–7. J Hazard Mater 2007. In: Proceedings of the 19th Industrial waste conference. [168] Mancy KH.287:14–24. J Colloid Interface Sci 2006. J Chem Technol Biotechnol 1987. Pena ML. Li HT. Wang S. Aydiner C.79:264–73.14:43–7. Demirbas E. Bussakorn PW.16:109–20. [182] Wang S. [215] Ahmaruzzaman M. Process Biochem 2003. J Colloid Interface Sci 2004.212:282–93. [161] Gupta VK.264:17–28. Mohan D. Kumar S. Ind Eng Chem Res 2002. [175] Gupta VK. [172] Acemioglu B. Kara S. Chemosphere 2005. Potential of rice husk and rice husk ash for phenol removal in aqueous systems. Cheng SL. Colloid Surf A 2005. [207] Banerjee SS. Waste Manage 2001. Role of unburnt carbon in adsorption of dyes on fly ash.114:423–38.150:737–46.10:249–60. [160] Gupta VK. Sharma DK. Removal of DDD and DDE from wastewater using bagasse fly ash. Choueib A.37:13–24. Chemosphere 2005. Removal of basic dyes (rhodamine B and methylene blue) from aqueous solutions using bagasse fly ash. Adsorption and detection of some phenolic compounds by rice husk ash of Kenyan origin.38:99–104. Yang H. Production of granular activated carbon from fruit stones and nutshells andevaluation of their physical.40:87–96.272:89–104. 1988. [212] Kaleta J. [169] Jain KK. Dyes Pig 2007. CD-ROM. Menahem R. Li L. Ali I. Sorption of dyes from aqueous solutions onto fly ash. Water Res 2001.24:45–50. [156] Srivastava VC. Verstraete W. [208] Polat H. Mittal A. Colloids Surf 1988. In: Proceedings of ICCS&T. [220] McKay G. A comparative study of dye removal using fly ash treated by different methods.871:193–200. [195] Gupta VK. Deb PK. IPPTA: Q J Indian Pulp Paper Tech Assoc 2002. Fly ash as a sorbent for the removal of biologically resistant organic matter. Zhu ZH. Removal of dyes from wastewater using fly ash. Sharma SK.303:477–83. Panday KK. [189] Yamada K. Ersoz M.274:371–9. J Hazard Mater 2007. J Colloid Interf Sci 2005. J Hazard Mater 2007. Ali I.53:655–65. Yalcin M. Kustka M. Chandra S. Adsorptive removal of phenol by bagasse fly ash and activated carbon: equilibrium. In: Scientific Papers from Institute of Chemical Technology. Removal of detergent from wastewater by adsorption on fly ash. [185] Wang SB. [219] Namasivayam C. Geopolymeric adsorbents from fly ash for dye removal from aqueous solution. Removal of chrome dye from aqueous solutions by mixed adsorbents. Am J Appl Sci 2004. [174] Matheswaran M. [196] Mall ID. Environ Pollut Series B Chem Phys 1985. [213] Gupta VK. over bottom ash and de-oiled soya. vol.66:189–95. J Hazard Mater 2008. Srivastava VC. Water Res 2003. a low-cost adsorbent. [166] Solin V. Sorption of selected organic pollutants by fly ash. [162] Kumari K. Adsorption of Congo red from aqueous solution onto calciumrich fly ash. Dogar C. Effect of quaternary ammonium cations on dye sorption to fly ash from aqueous media. Removal and recovery of the hazardous azo dye acid orange 7 through adsorption over waste materials: bottom ash and de-oiled soya. Singh VN. Removal of Orange-G and methyl violet dyes by adsorption onto bagasse fly ash-kinetic study and equilibrium isotherm analyses. Kobya M. Eslami A. Colloids Surf A-Phys Eng Aspects 2006. Joshi MV. Boyjoo Y. Ind J Environ Health 1974. 2. Water Qual Res J Canada 1999. Ind Eng Chem Res 2005. Removal of victoria blue from aqueous solution by fly ash. Prasad B. Removal of phenol from aqueous solution by adsorption. Adsorption-deadsorption of trichlorophenol in watersoil systems. J. [159] Lorenz K.126:71–7.M. Buchtova H. Atun G. J Colloid Interf Sci 2006. Secondary treatment of power-plant phenol waste with fly ash and cinders.45(4):1446–53. Mittal A. Paper No. Choueib A.98:140–4. Van der Bruggen Bart. Colloids Surf A: Physicochem Eng Aspects 2006. Zhu ZH. [184] Vandenbusch MB.69(5):1032–8. Suba S. Sell NJ. Removal of lindane and malathion from wastewater using bagasse fly ash – a sugar industry waste.33:55–61. J Chem Technol Biotechnol 2005. p. [155] Damaris NM. [191] Gupta GS. [164] Nollet H. p. Dizge N. Equilibrium and kinetic mechanism for Reactive Black 5 sorption onto high lime Soma fly ash. [201] Li L. [158] Ugurlu M. Uptake of dyes by a promising locally available agricultural solid waste: coir pith.1:321–6. [171] Hung YT. Gesubdb Lng 1954. Sonochemical treatment of fly ash for dye removal from wastewater. Aydin ME. Removal of dyes from aqueous solution using fly ash and red mud. Boyjoo Y.36:2483–90.129:133–42. Colloid Interface Sci 2005. Ind J Chem 1980. [218] Banat F. Zhu ZH. Water Sci Technol 1997. Mishra IM. Zhu ZH. [163] Rathore HS. [173] Mall ID. Van Der Meeren P. Wu HW. Ahmaruzzaman / Progress in Energy and Combustion Science 36 (2010) 327–363 [153] Singh AK. Srivastava VC. Use of cellulose-based wastes for adsorption of dyes from aqueous solutions. bagasse ash and wood charcoal. Duman I. [204] Mohan D. J Colloid Inter Sci 2006. [179] Wang S. Water Air Soil Pollut 1999. Lutgen P. Krishnan L. Gajbe V. Ng E. 116. Dye adsorption on unburned carbon: kinetics and equilibrium. [186] Wang SB. [193] Gupta VK. Srivastava VC.6:95–116. Gajbe V. Ryznarova M. In: International Ash Utilization Symposium. Ramakrishna KR. Chem Eng J 2007.293:16–26. Prasad G. Removal of dyes from aqueous solution by sorption with coal fly ash. Removal of phenols from water environment by activated carbon. Agar NK. Fly ash for colour removal from synthetic dye solutions. Singh G. Removal of congo red from aqueous solution by bagasse fly ash and activated carbon: kinetic study and equilibrium isotherm analyses. Agarwal NK. Prasad G. [209] Tor A. Cu. Paul MS. Vandecasteele Carlo. Mall ID. Evaluation of the use of raw and activated date pits as potential adsorbents for dye containing waters. Batch adsorption of organic pollutants from oxidation pond effluents using fly ashes. Int J Env Pollut 2006.21:261–70. 2003.11:87–97. Bioresour Technol 2007. Juang RS. Dye removal using low cost adsorbents. Cheremisinoff PN. [188] Wu HW.B126:91–5. Sharma S. [157] Mukherjee S. p. Boyjoo Y. Properties of large unburnt char particles in fly ash from pulverised-fuel power stations and implications in beneficial separation and utilization. chemical and adsorption properties. Mall ID. [217] Aygu¨n A. Gacho CC. Fan M. Mall ID. Radhika R.33:546–51. 1965. Mishra IM. [210] Thawornchaisit U. Sep Purif Technol 2004. Jayaram RV. 146–60. Wang SB.B92:263–74. Modeling the effects of adsorbent dose and particle size on the adsorption of reactive textile dyes by fly ash. [214] Gupta VK. Singh D. Use of bagasse fly ash as an adsorbent for the removal of brilliant green dye from aqueous solution.80:1204–9.41:3688–95. University of Kentucky. Oxidative decolorization of reactive dye solution using fly ash as catalyst.75:189. Mittal A. Molva M. 74:1226–31. Ahmaruzzaman / Progress in Energy and Combustion Science 36 (2010) 327–363 [221] Kannan N. Untreated coffee husks as biosorbents for the removal of heavy metals from aqueous solutions. Haim C. Evans CA. vol. Plana F. J Chem Technol Biotechnol 2001. Etchebers O. Resource recovery of waste fly ash: synthesis of zeolite-like materials. [285] Zhao XS. Kinetic sorption modelling of Cu. 46:1319–31. MAS NMR and XPS.30:5777–83.21:383–402. Steenbruggen G. [229] Allen SJ.9:224. [260] Erol MS. Treatment of acid mine drainage with fly ash: removal of major contaminants and trace elements.76:9–26. Adriano DC. Biochem Eng J 2003. Effects of aging and seeding on the formation of zeolite Y from coal fly ash. Environmental assessment of coal ash disposal: a review. Brummer M. [264] Eary LE. [256] Stewart BR. Zhu HY. Nippon Kagaku Kaishi 1992. [281] Querol X. [234] Ahluwalia SS.77:377–81. Goyal D. Garcia AI. [258] Pe´rez-Lo´pez R. Hollman GG. Grimm SR. [226] Dimitrova SV. J Environ Qual 1990. [251] Eisenberg SH. Adsorption properties of activated carbon from waste newspaper prepared by chemical and physical activation. Untersuchungen u¨ber die Bildung von Analcim aus natu¨rlichen Silikaten. [270] Warren CJ. [237] Gharaibeh SH. Gladney ES. [246] Fischer GL. Moran A. Haghnia GH. [266] Spears DA. Etchebers O. Process Biochem 2005. J Colloid Interface Sci 2004. Resour Conserv Recycl 2005. ˜ a JC.85(4):883–90. Stud Surf Sci Catal 1997. Sorption of dyes and copper ions onto biosorbents. Almodo´var GR. Schultze LE. [236] Li YS. MJ.5:484–92.15:59–68. Cama J.40:997–1026.18:181–6. J Environ Manage 2007. et al. Soroezak MM. Chemical neutralization of acidic wastes using fly ash in Israel. Appl Clay Sci 1996. [276] Zamaow. Geological Society of London. Dhanpat R. et al. Chandra K.9:1173. Chang DPY. Dyes Pigm 2005.99:1571–7. [248] Menon MP.33:1464–9. Secondary mineral formation in coal combustion byproduct disposal facilities: implications for trace element sequestration. Gagajena RC. [228] Guo X. p.10:369–78. Johnston HM. Characterizating the surface of environmental particles. Special Publications. J Environ Sci Health 1986. Key DL. Schifter I.71:1921–34. microcrystalline structures and the mystery of spheres. Environ Sci Technol 1984.63:21–43. Adriana SF. The adsorption of SO2 by zeolites synthesized from fly ash. Pal N. In: Adnano DC. uses and treatments of combustion ashes: a review. [230] Guibal E. Studies on the uptake of lead and zinc by lignin obtained from black liquor-a paper industry waste material. Metal complexation by chitosan and its derivative: a review. Ion exchange reactions in zeolites. Lopez-Soler A. Ulubas T. Adsorption of phenolic compounds on low-cost adsorbents: a review. [252] Hansen LD. Chemical speciation of elements in stack collected respirable size coal fly ash.19:202–14. [253] Mohapatra R. Angel LS. [263] Gitari MW. structure.30:228–32. Kirkpatrick RJ. Tyagi R. Foftschritte der Mineralogist 1985. Passive neutralization of acid mine drainage by fly ash and its derivatives: a column leaching study. J Hazard Mater 2008. Environ Sci Technol 1995. [268] Doye I. Environ Technol Lett 1988. Nieto JM.262:194–9. Ind Eng Chem Res 1998. Ithamar P.105:1565. Application of biosorption for the removal of organic pollutants: a review. chemistry. Eatough DJ. Moran M. Energy Convers Manage 2005. 2004.13:435–50.19:454–62.46:1–27. p. In: Giere´ R.27:80–94. Soto B. and coal fly ash zeolites and their amorphous precursors by IR. 2004. [227] Srivastava SK. Stille P. Environ Sci Technol 1978.37:71–8.152:1073–81. Hayashi H.18:1197–213. [261] Polat M. Alastuey A. Kinetic and equilibrium modelling of the methylene blue removal from solution by adsorbent materials produced from sewage sludges. Rozada F. Progress in zeolite and microporous materials.12:768–73. Zn. Hayashi H. Ersoy-Mericboyu.15:353–60. Chemical characteristics of selected fly ash leachates. Ku¨cu¨kbayrak A. Demirbas O. Van Grieken R. Natusch DFS. A general method for the conversion of fly ash into zeolites as ion exchangers for cesium. Interactions of metal ions with chitosan-based sorbents: a review. Petrik LF. Eli L. Cikla S. J Sci Ind Res India 1996. Rakotoarisa Z. Determining controls on element concentrations in fly ash leachate. Singer A. FL TIC: Robert E. J Hazard Mater 2008. [259] Gitari MW.97:1061–85. Comparison of limestone. Barral MT. Nunez A. High capacity cation exchanger by hydrothermal zeolitization of coal fly ash. [286] Chang HL. Idaho. Fuel 1999. J Environ Qual 1985. Adsorbent properties of red mud and its use for wastewater treatement. Shih WH. editors. Synthesis of zeolites by alkaline activation of ferro-aluminous fly ash.50:343–53. Alastuey A. Kim TS. Disposal. J Mater Sci 1995. Khan ARM. Hydrothermal reaction of a rhyolitic-composition glass. Al-Kofahi MM. [222] Okada K. Dudas MJ. Na–A. Chemical characterization of fly ash aqueous system. Miner Eng 2006. [233] Tee TW. Removal of lead cadmium and zinc by waste tea leaves. Janssen MJ.55:77–93. [265] Donahoe RJ. utilisation and environmental effects of fly ash. J Hazard Mater 2002. Linton RW. Wirsching U. [225] Srivastava SK. [262] Potgieter-Vermaak SS. Potgieter JH. a solid-state NMR study. [240] Crini G.32:1314–22. Rubinos D.55:772–80. Proceedings of the symposium on environmental chemistry and cycling processes. [241] Alkan M. Czank CA. [288] Shigemoto N. J Environ Sci Health – Part A 2006. Water Res 1996. [279] Berkgaut V. J Colloid Interf Sci 2003. Kameshima Y. Science 1976. [245] Iyer R. Fuel 2001. Removal of reactive blue 221 and acid blue 62 anionic dyes from aqueous solutions by sepiolite.360 M. Iwuoha E. Dhar BB. Metal sorption on blast furnace slag. Calvo LF. Water Res 1998.31:2527–33. Yasumori A. Tittlebaum ME. Solubility of trace elements in coal fly ash. Jose LFT.26:1417–24. dolomite and fly ash as pre-treatment agents for acid mine drainage. Ni. Removal of Cu2þ and Pb2þ in aqueous solutions by fly ash. Waste Manage Res 1995. vol.51:25–40. waste and the environment: a geochemical perspective. Fisher GL. Appl Geochem 2003. Mattigod SV. Removal of selected heavy metals from aqueous solutions using processed solid residue of olive mill products. Dogan M. Castillo S.14:405–10. Adsorption of metal ions on lignin. Kinetics and mechanism of removal of methylene blue by adsorption on various carbons – a comparative study. Lo´pez-Soler A. Pb and Cr ions to pine bark and blast furnace slag by using batch experiments.192:553–5. Bioresour Technol 2008. [224] Lopez E. Rao JR. Non-conventional low-cost adsorbents for dye removal: a review. Key DL. Determination of model parameters for zinc (II) biosorption onto powered waste sludge (PWS) in a fed-batch system. Fast method for recycling fly ash: microwave-assisted zeolite synthesis.9:1223–32. Shirakami S. Lu GQ. Bioresour Technol 2006. [283] Srinivasan A. Jackson ML. Environ Sci Technol 1996. Sep Purif Technol 2004.78:1225–30. Porter JF. [271] Breck DW. J Geochem Explor 1998. [231] Ho YS. Owens JW. J Hazard Mater 2006. Brubus FL. Amanios T. Hirano S. Ainsworth CC. [239] Nehrenheim E.41(8):1729–47. McKay G. Sonia DR. Leandro SO. [250] Dressnen DR. Iwuoha E. Carbohydr Polym 2004. Okujeni C.93:321–9.151:134–42. Uman Synthesis of Na zeolites from fly ash in a pilot plant scale: Examples of potential environmental applications. [277] Lin CF. [247] Keyser TR. J Chem Tech Biotechnol 2002. Water Res 1998. Sundaram MM. A two-step process for synthesis of zeolites from coal fly ash. Preparation and characterisation of zeolites from coal fly ash. A review of chitin and chitosan applications. 220–2211. Process Biochem 2003. 641–658. The synthesis of zeolites from fly ash and the properties of the zeolite products. Kennedy JF.67:1637–46. In: Zeolite-93. [257] Pe´rez-Lo´pez R. editors. Utilization of fly ash to improve the quality of the acid mine drainage generated by oxidation of a sulphide-rich mining waste: column experiments.30:735–42. Environ Sci Technol 1999. Chemosphere 2007. [267] Tiruta-Barna L. [287] Hollman GG.143:48–67. 1976. Zeolites formation from fly ash. Review of the minor elements. Chiou CS. Water Air Soil Pollut 1980. Nieto JM. Zhang S. Salas P. J Environ Qual 1980. Alastuey A.75:1009–19. [223] Otero M. Wanger LE. React Funct Polym 2000. [238] Waleska EO. Fuel 1995.4:245–52. [255] Prasad B. The iron-coating role on the oxidation kinetics of a pyritic sludge doped with fly ash. and use. [289] Shigemoto N. Formation of secondary minerals in artificially weathered fly ash. Environ Technol 1994. [278] Amrhein C. [249] Elseewi AA. Evaluation of leachate quality from codisposed coal fly ash and coal refuse. [235] Kargi F. J Environ Qual 1997. .87:1637–50. Pant N. [272] Querol X. Dayal R. Monama P. Plana F. Ghuman GS. Dyes Pigm 2001.62:305–9. Page AL. [273] Holler H. Liu CC.5(2):158–62. Geochim Cosmochim Acta 2007. Neutralization of acid mine drainage with alkaline industrial residues: laboratory investigation using batch-leaching tests. p. Contrib Mineral Petrol 1970. [254] Reijnders L. Fuel 2008. His HC. Medinaceli A.43:313–36. Malabar.137:1466–78. Characterization of Na–X. Geochemistry of leachates from coal ash. 1993. Daniels WL. Celikcapa S. Removal of heavy metals by waste tea leaves from aqueous solution. Some aspects of characterisation. Banerjee NN. Eng Life Sci 2005. [269] Reardon EJ. [232] Ravi Kumar MNV.38:1047–61.29:1109–17. Assessment of the multi-scale leaching behaviour of compacted coal fly ash. In: Geological Society of London. Special Publications. Gustafsson JP. [275] Ho¨ller H. Grutzeck MW. 236. Silberman D. 1984 (Chapter 7) p. Adsorption of Cr(III) from wastewater by wine processing waste sludge. Environ Sci Technol 1997. Warren CJ. [280] Salinas EL. Sugiyama S. Ayora C. Mogica E. Me`hu J. James J. Physico-chemical characteristics of water extracts of different coal ashes and fly ash amended composts.273:95–101. In: Zeolite molecular sieves. [284] Querol X. Abu-El-Shar WY.38:43–74. Adv Colloid Interf Sci 2008. [244] Aksu Z.80:857–65. Geochemical factors controlling the mobilization of inorganic constituents from fossil fuel combustion residues: II. Mosher PA. Krieger Publishing. Deshpande SV. [243] Ahmaruzzaman M. Adsorption isotherm models for basic dye adsorption by peat in single and binary component systems. Duchesne J.280:322–33.32(2):498–502. Energy. Yamamoto N. [274] Yang WH. p. Am Mineral 1990. Synthesis and properties of zeolites from coal fly ash. [282] Steenbruggen G. The surface chemistry of leaching coal fly ash. 250–1.65:251–9. Environ Technol Lett 1998. 236. Singh AK Sharma A. J Porous Mater 1997. Arias M. J Colloid Interf Sci 2004. 245213. Shan X. Petrik LF. 619–39. Lee S. Bhattacharjee G. [242] Varma AJ. Eaton HC. Okujeni C. Fly ash collected from electrostatic precipitators. McKay G. In: Proceedings of international conference flyash India 2005. Onodera Y. [306] Mimura H. ACI Mater J 1994. Roller compacted concrete for highway pavements. 2005.95:454–62.92:512–7. Molten-salt method for the synthesis of zeolitic materials: II. [336] Bouzoubaaˆ N. Khlaifat A.86:507–14.1:61–70. Int J Water 2000. [317] Mehta PK. J Environ Manage 2008. Process for preparing artificial zeolite by a slurry reaction method. Onozakia M. Kumar S. [337] Antiohos SK. Strength and durability considerations affecting mix proportions of concrete containing fly ash. properties. [313] Woolard CD. 994.M. Zhang Z. Paul AM. Heo NH. Effects of fine aggregate replacement on the rheology. [297] Katayama Y. [302] Wu D.84:1455–61. Strong J. Ind Eng Chem Res 2007. ACI Special Publication 1998:401–10. [342] Antiohos SK.38:766–72. Recovery of heavy metals from electroplating sludge and stainless steel pickle waste liquid by ammonia leaching method. Cem Concr Res 1986. 2003. Cem Concr Compos 1990. Curr Sci 2007. 10/3/2006. Adsorptive removal of thiophene and benzothiophene over zeolites from Mae Moh coal fly ash. [334] Singh M. ON: University of Toronto Press. Englewood Cliffs. Li X. [328] Maslehuddin M. Concrete incorporating high volumes of ASTM Class F fly ash. [351] Fukute T. Lim WT. Zeolite formation in alkaline molten-salt system. Increasing coal fly ash use in cement and concrete through chemical activation of reactivity of fly ash. [350] Delagrave A.18:33–8. [340] Lupu C. Adv Eng Mater 2006. [318] Mehta PK. Yildiz R. Arsenate removal from water by an alumina-modified zeolite recovered from fly ash. [314] Price GC.85:505–11. X. Jackson KL. New Delhi: Allied Publishers.35:1165–71. Control over cement setting through the use of chemically modified fly ash. Chem Eng J 2008. and calcium carbonate pretreatment of fly ash: the effect on setting of cement–fly ash mixtures. Tsimas S. SP-132. Jackson KL. Cation exchange properties of hydrothermally treated coal fly ash. [346] Kumar S. WI. Appl Geochem 2002. Noguchi T. Farmington Hills. [341] Lupu C. Fuel 2004. Improvement of characteristic of roller compacted oncrete by classified fly ash. Mishra IB. Utilisation of high volume of blast furnace slag and fly ash in blended cements through high energy milling. Innovative methodologies for the utilisation of wastes from metallurgical and allied industries. Performance characteristics of high-volume Class F fly ash concrete. Removal of mixed heavy metal ions in wastewater by zeolite 4A and residual products from recycled coal fly ash. Mangrulkar PA. [305] Somerset V. Zheng Y. Katayamaa Y. Wang C. Pavasant P. [339] Dhir RK.87(1):125–31. Concrete structure. [294] Park M.87:2347–51. Mehta PK. Fuel Process Technol 2004.17:1159–64. Fuel 2008. 113–20. An experimental study on strength development of concrete containing fly ash and optimum usage of fly ash in concrete. Akiba K. Tedros A. 1995. Singh SS. [291] Singer A.1– 11. [293] Park M. Irene R. [325] Alasali MM.599. Removal of Arsenic from drinking water using modified fly-ash bed. 1991. He S. Malhotra VM. Tomosawa F.86:58–62. Cem Concr Res 2005. Mehrotra SP. 361 [324] Malhotra VM. Murayama N. [326] Bilodeau A. Yamamoto H. Chao CYH. 1986. ACI Mater J 1989. 2005. Environ Sci Techniol 1995. Sreenath HG. Papadakis VG. Chen Y. [295] Chareonpanich M. Fukudac T. J Environ Sci 2007.12:271–7. Cem Concr Res 1999. Hayashi H.37:91–8. Constr Build Mater 2008. Peterson R. Lu X. Cem Concr Aggreg 1994.83(6). In: Proceedings of the American Concrete Institute.19:540–5. Jadhav PD. [323] Langley WS. Irene R. [322] Giaccio GM. slag. Tews JH. Water. Mater Res Soc Symp Proc 1988. SP-178.11(3):381–4. ACI Mater J 1991. Berkgaut V. Takami Y.29:550–8. Kot SC. [303] Qiu W. ACI Mater J 1997.91:3–12. Wang Y. March 1980: p. Rajnikanth V. Yokota K. [312] Ngamcharussrivichai C. Concr Int 1996. Bard S.116:987–91. Cem Concr Aggre 1988.39:1748–53. Ludwig D. [320] Zhang Y. Gholam HH. J Colloid Interface Sci 2006. 1961. p. [296] Moriyamaa R. [315] Dunstan ER. Fuel 2005. Proceedings of the fourth CANMET/ACI International conference on the use of fly ash. [292] Amrhein C. Rayalu SS. Synthesis of ZSM5 zeolite from lignite fly ash and rice husk ash. 137.78:137–42. Jr. Garg M. Choi CL. Bansiwal AK. Hu Z. 0644DEL2006. Effect of fly ash composition on sulfate resistancew of cement. ACI Mater J 1998. Barron AR. Cem Concr Res 2004. Adsorption of phenol and o-chlorophenol on surface altered fly ash based molecular sieves. Barron AR. Erasmus CR. Mechanical properties and durability of concrete made with blended fly ash. compressive strength and carbonation properties of fly ash and mortar. Kongkachuichay P. Cem Concr Res 2001. Carette GG. Bandopadhaya A.13:401–6. Ramme BW.113:145.16:12–20. Kumar S. Heo NH.30:735–42. [344] Kumar S. Fly ash: towards sustainable solutions. Petrik L. Molten-salt method for the synthesis of zeolitic materials: I. Simultaneous removal of NH4 and PO3 4 in aqueous solution and its mechanism by using zeolite synthesized from coal fly ash. silica fume.85:1623–34. Devotta S. acid. Pigeon M.10:88–95. Reinhardt WG. [331] Naik TR. Hami M. Shiotac K. [332] Hwang KR. In: Lakshmanan N. Fuel 1999.22: 1191–200.28:4781–6.300:491–7. Marchand J. Removal of phosphate from aqueous solution by zeolite synthesized from fly ash. Simultaneous removal of ammonium and phosphate by zeolite synthesized from fly ash as influenced by salt treatment. New York: McGraw-Hill. Wu D.12. Kong H. [335] Oner A. Effects of fly ash on the properties of environmentally friendly dam concrete. Xu X.138:73–83. Mining Mater Process 2000. Bard S. Qian J. p. Cem Concr Res 1983. [308] Hui KS. Tai SK. Mechanical properties and durability of concrete made with high-volume fly ash blended cements using a coarse fly ash. and materials. Lin H. [329] Tikalsky PJ. US Patent No. NJ: Prentice Hall. Alex TC. Turkey. Rayalu SS. p. [349] Nanni A. Surface-modified zeolite – a sequestration of arsenic and chromium anions. Chaniotakis E. zeolite from coal fly ash by fusion with sodium hydroxide prior to hydrothermal reaction. [316] Mehta PK. Ryan CG. [304] Goswami D. Cem Concr Compos 2007. J Hazard Mater 2007. Shibata JJ. Miyaura K. Fuel 2007. Hou J. Wu D. Las Vegas. 2006. USA. [310] Kumar P.16:227–38. J Environ Sci China 1999.96:164–9. [307] Shawabkeh R. ACI Mater J 1989. Malhotra VM. Energy Sources 2003. J Nucl Sci Technol 2001. Development of chloride-resisting concrete using fly ash. Qi T. Nakano K. [298] Takami Y. Influence of quicklime addition on the mechanical properties and hydration degree of blended cements containing different fly ashes. Microporous Mesoporous Mater 2000. Mechanism of sulfate attack on portland cement concrete – another look. Kumar R. Mehrotra SP. Jones MR. Choi J. Deicer salt scaling resistance of roller compacted concrete pavements. Ogawa K. Ramme BW.11.861:208–11. Iwuoha E. Boisvert J. Durability of concrete incorporating high volumes of fly ash from sources in the USA.34:487–93. Cementitious binder from fly ash and other industrial wastes. SF. [309] Apiratikul R. Lim WT. 367–383. Kong H. ACI Mater J 1998. Concrete incorporating high volumes of ASTM class F fly ashes: Mechanical properties and resistance to deicing salt scaling and to chloride-ion penetration. Proceedings of the international conference on advances in concrete composites and structures (ICACS-2005). Selective formation of Na–X. p. Al-Harahsheh A. [333] Siddique R. Chem Eng J 2008. Drying shrinkage of roller-compacted concrete for pavement applications. slag and natural pozzolans in concrete. Wang Z. ACI Mater J 1988. [352] Pittman DW. [330] Naik TR. Papageorgiou A. Carrasquillo RL. Carrasquillo PM. Sep Sci Technol 2003. Characterization of zeolitic materials. Chatratananon C. [301] Zhang B. Papageorgiou D. J Hazard Mater 2005. Alkali hydrothermal synthesis of zeolites from coal fly ash and their uptake properties of cesium ion. Prasassarakich P. Bandopadhyay A.95:19–25. Painter KE.29:309–14.144(2):245–58.304:300–6. editors.37:81–9. et al. Das AK. et al.768253. In: Malhotra VM. Yoshida S. Nuntang S. Conversion of oil shale ash into zeolite for cadmium and lead removal from wastewater. J Am Concr Ins 1986. Role of concrete incorporating high volumes of fly ash in controlling expansion due to alkali–aggregate reaction.148:721–6. Wang Z. Effect of sand replacement on the early-age strength gain and long-term corrosion-resisting characteristics of fly ash concrete. Sorption of Cu2þ. Kim MC. Takedab S. Resour Conserv Recycl 2006. Use of high volumes of class C and class F fly ash in concrete.88:159–63. Zhang B. Ragan SA. Simultaneous removal of ammonium and phosphate by zeolite synthesized from coal fly ash as influenced by acid treatment. Performance of concrete. Malhotra VM. Zhang MH. Patent Application No. Ishii M. Large-scale synthesis of artificial zeolite from coal fly ash with a small charge of alkaline solution. Environ Sci Technol 1996. ACI Special Publication. Akyuz S. Shibata J. J Mater Sci 1993. Mitra BK. [347] Kumar R. Limtrakul J. USA: American Concrete Institute. [348] Hansen KD. Zhang Z. editor. Kong H. Ahmaruzzaman / Progress in Energy and Combustion Science 36 (2010) 327–363 [290] Shigemoto N. Istanbul. [327] Bilodeau A. Shoenberger J. et al. Milwaukee. Choi J. SP-153. Properties of fresh concrete containing large amounts of fly ash. and natural pozzolans in concrete.48:301–14. [299] Murayama N. Malhotra VM.46:8018–25. [300] Chen J. p. Malhotra VM. Kim MC. Durability of concrete incorporating high-volume of lowcalcium (ASTM class F) fly ash. 30. An improved process for the production of blended cement containing higher proportion of fly ash using high energy milling. Malhotra VM. Alkaline hydrothermal conversion of fly ash precipitates into zeolites 3: the removal of mercury and lead ions from wastewater. Roller-compacted concrete dams. Gopalkrishnan S. Choi CL. [338] Gao P. Synthesis and properties of zeolites from coal fly ash. Proceedings of the fifth international conference on FA. [345] Kumar R. Toronto. Yamamoto H.494. Cd2þ.38:113–30.8: 576–80. [311] Kamble SP.25:617–28. Li C. Namto T. Evaluation of the use of modified coal ash as a potential sorbent for organic waste streams. p. 319–49. [343] Shi C. Structural concrete incorporating high volumes of ASTM Class F fly ash. Khan ZH. [319] Mehta PK. J Colloid Interf Sci 2006.83:981–5. 2003. 1992. 6. [321] Ravina D. Mechanical and durability characteristics of gypsum-free blended cements incorporating sulphate-rich reject fly ash. and Pb2þ using modified zeolite from coal fly ash. Microporous Mesoporous Mater 2000. Tsimas S. Sivasundaram V.B127:89–101. Michigan. .31:1393–402. AU patent No. p. Parametric study of the column oil agglomeration of fly ash. Robl TL. O properties of roller compacted concrete containing a non-standard high calcium fly ash.S. 1st ed. Cem Concr Res 2000. Trin 1: Gennemgang af recepter. Leeds University. Suuberg EM. Dry beneficiation of high loss-on-ignition fly ash. Dam-Johansen K.35:257–60. U. 1997. Design and properties of high volume fly ash concrete for pavements. [369] Halit Y. Wang YC. patent no. Celik ON. Size distribution and combustion reactivity.58:233–41. Composition of reactive powder concretes. [404] Niewiadomski M. Prog Energy Combust Sci 2008. England. Tanrikulu AH. Rathbone RF. Cem Concr Res 1995. [385] Hachmann L. Cem Concr Res 1997. 129–64. MSL 94–45 (IR). Dry triboelectrostatic beneficiation of fly ash. Malhotra VM. 2000. Characterization of carbon concentrates from coal-combustion fly ash. [364] Kejin W. de la Torre MJ.78:121–32. Cem Concr Compos 1998. DC: US Department of the Interior. Mag Concr Res 2006. El Sayad HI. Utilization of fly ash and ground granulated blast furnace slag as an alternative silica source in reactive powder concrete. Zhang DS. [372] Nisnevich M. [407] Baltrus JP. Application of admixtures in concrete. Cazalla O. [400] Soong Y. 213–25.21:182–9. Bilim C. 103–142. Constr Build Mater 2009. [412] Wiebusch B. Fuel 1997. Zhang L. Residual carbon from pulverized coal fired boilers: 1. Study on fired bricks with replacing clay by fly ash in high volume ratio. Ullmann R. Are we placing too much air in our concrete? Concr Constr World Concr 2004. Eshel Y. Fuel 1999. Soong Y. Concrete admixtures. In: The US Department of the Interior. [396] Hurt RH. Wells AW. Maroto-Valer MM. A study of the characteristics of heat of hydration of PFA concrete in thin structures. Proceedings of the Combustion Institute 1998. RI. Bergougnou MA. [377] Rixom MR.23:1178–84. Recovery of coke fines from fly ash by air sparged hydrocyclone flotation. Denmark: Danish Technological Institute. Constr Build Mater 2007. Hurt RH. [403] Zekel LA. [363] Richard P. 1986. [365] Massidda L. Relation between abrasion resistance and flexural strength of high volume fly ash concrete. [384] Lane DS.69(2):240–6.6:117–25. ACI Special Publication 1994. [388] Helmuth R. Bittner JD. SP 200-27. [374] McCarthy MJ. Hower JC. Shrive N. [409] Fahriye K. Sertaç A.55:313–20. Technical report 1. Ku¨ laots I. [362] Richard P. Cem Concr Res 1997. Nanru Y. Graham UM. Strength [360] Atis CD. Iowa State University. First international conference on the use of fly ash. Constr Build Mater 2007.36:251–8. [397] Ban H. Seyfried CF.80(6):867–71.58:1446–50.25:1501–11. Tao W. [395] Chen X.103:444–51. Xiao B. Fly ash in concrete. Cheyrezy M. In: Proceedings of the Canmet/ACI.48(6):47–50. Diehl JR. [373] Nisnevich M. Mag Concr Res 2003. Civil Engineering Department. Killmeyer RP. Sirotin G. Lime based steam autoclaved fly ash bricks. Andre´ sen JM. Chemical admixtures for concrete.87:1610–6. Civil Engineering Department. Fly ash addition in clay materials to improve the quality of solid bricks. Suuberg EM.19:56–60.136. [408] Pedersen KH.19:243–7. [354] Wolley GR. Aggarwal R. White CM. 1995. Jones RJ. Schlesinger T. Eshel Y. Zhang MH. Champagne KJ. [417] Cultrone G. Hurt RH. J Hazard Mater B 2006. Shang L. Energy Fuels 2001.21:61–4. [361] Zhang Y. Electroseparation of fly ash of coal combustion for power generation. Thompson WG. Suuberg EM. Gao Y-M. 1st ed. Tanriverdi M.890. et al. Evaluating properties of blended cements for concrete pavements.27:2965–71. Chiu CT. Selective beneficiation for high loss-of-ignition fly ash.33(12):2091–9. Hower JC. Chen X. Providence. A review of the interference of carbon containing fly ash with air entrainment in concrete. Standard specification for fly ash and raw calcined natural Pozzolan for use as a mineral admixture in portland cement concrete. 2nd ed. [418] Cultrone G. [414] Yang J. Sebastia´n E. [389] Baltrus JP. [371] Nisnevich M. Mailvaganam NP. Mehta A. Sep Purif Technol 2002. 95–100. London: E & FN Spoon. Constr Build Mater 2005. U. Measurement of adsorption of airentraining admixture on fly ash in concrete and cement. Jensen AD. Lightweight concrete containing thermal power station and stone quarry waste.23(2):687–93. Wei G. 1994. Concr Int 1997. Wang T. 1st ed. Skjøth-Rasmussen MS. Limbachiya MC. [376] Bruere GM. Interactions of carboncontaining fly ash with commercial air-entraining admixtures for concrete. Hurt RH. [359] ASTM C-618. Ozonation for the chemical modification of carbon surfaces in fly ash. Karabulut AS. IEEE Trans Ind Appl 1977. Mater Struct . Physical cleaning of high carbon fly ash.26:177–84. Schaefer JL. Solidification/stabilization of heavy metalloaded red muds and fly ashes.15(2): 455–62. An industrial evaluation of fly ash bricks. Civil Engineering Department. UK. Borys B. Cocco E. Ozone treatment of fly ash. The process and mechanism of alkali-silica reaction using fused silica as the reactive aggregate. In: 2000 Conference on unburned carbon on utility fly ash. Hsu A. Hu¨seyin Y. silica fume. Li TX. Brown JD. A preliminary study of reactive powder concrete as a new repair material. Fuel 2002. Soong Y. Leeds University. Meloni P. Burnett A. Bureau of Mines. Hurt R. Towards maximising the use of fly ash as a binder. Feasibility study of using brick made from municipal solid waste incinerator fly ash slag. LaCount RB. Ultra high performance concrete (UHPC).200:447–64. 2002. In: International symposium on ultra high performance concrete. [356] Atis CD. 58–64. Champagne KJ. [380] Nasvik J. J Eur Ceram Soc 2004. October 2000.24:547–64. Sebastia´n E. Diehl JR. Unpublished PhD thesis. J Chem Technol Biotechnol 1997. 6. Stencel JM. p.78(2):161–8. [401] Inculet II.87(12):2401–7. US Department of Energy. An examination of fly ash carbon and its interactions with air entraining agent.089.76(8):761–5. Fuel 2008. Hupka J. [383] Dhir RK. Center for Portland Cement Concrete Pavement Technology. Schoffstall MR. Final report. Annual book of ASTM standards.74(4):471–80. Sun W. Solid Fuel Chem 2004. [387] Freeman E. [405] Baltrus JP. ACI Mater J 2006. [419] Xu L. [375] Paille´re AM. J Appl Chem Biotechnol 1971. [398] Gray ML. Improving lightweight concrete with bottom ash. 1–4. [415] Lingling X. Gray ML.80(5):765–8. [355] Gaafar BA. Suuberg EM. 17–22.144:507– 18. Effects of fly ash on the air-void stability of concrete. Providence. Soong Y. ‘‘Ecological bricks’’ made with clays and steel dust pollutants. Fly ash in cement and concrete. The economic aspects of admixture use.51(1):53–64. [379] Dodson VH. Sevim UK. Sirotin G. Sanna U.11:237–49. 6.27:1093–8. Fuel 2001. et al. Sarkar SL. Cem Concr Aggregates 1991. Optimization of mechanical properties and durability of reactive powder concrete. Pistilli M. [370] Nisnevich M. [358] Wilson M. CO) 1996. Baradan B. Apparatus and method for deactivating carbon in fly ash. Pulverized fuel ash concrete: air entrainment and freeze/thaw durability. Study on fired bricks with replacing clay by fly ash in high volume ratio. Ahmaruzzaman / Progress in Energy and Combustion Science 36 (2010) 327–363 [353] Malhotra VM.30(7):1037–46. Zhi G. et al. Commercial separation of unburned carbon from fly ash. Zou Y. Cheyrezy MH. Champagne KJ. [381] Hasholt MT. 1. Karahan O. Rodriguez Navarro C. [410] Reidelbach JA. Cabrera JG. [394] Hurt R. Miller JD. patent no. 2nd ed. September 13–15 2004. [393] Keppeler JG. . 1991. [390] Gebler S. Washington. Constr Build Mater 2005.76(1):11–21. [392] Gao Y. Guo W.362 M. Fuel 2001. Information Circular Number 8488. Gibbins JR. Electrostatic separation of particles below 40 mm in a dilute phase continuous loop. [366] Shaheen E. 1987. Structural lightweight concrete based on coal ashes (containing undesirable radionuclides) and waste of stone quarries. Afklaring af problemer med NJV-flyveaske. [413] Lin KL. Schlesinger T. ACI Special Publication 2001. Gao Y-M. Testing fly ash in mortars for air-entrainment characteristics.38(3):72–81. CANMET. [357] Atis CD. Suuberg E. Fauth DJ. Air-entraining actions of anionic surfactants in Portland cement pastes. 80–82. London: E & FN Spoon. Ramezanianpour AA. Bokotko R. SP 144-24. Influence of mineralogy and firing temperature on porosity of bricks. [416] Cicek T. Full scale carbon burn-out and ammonia removal experience. Mag Concr Res 1999. Reat A. Liu W. UK. Fuel 1997. 1995. Knoer JP.137:1810–6.31(5):819–24. 1970. Surfactant adsorptivity of solid products from pulverized-coal combustion under controlled conditions. Suuberg E. CO) 1996. Burnett A. McCarthy MJ. Unpublished PhD thesis. Reactive powder concretes with high ductility and 200–800 MPa compressive strength. [368] Lee MG. May 2005.S.13(1):25–31. Radiological safety aspects of utilizing coal ashes for production of lightweight concrete. The effect of environmental curing condition on the gas and water permeability of concrete. Whitlock DR. Cem Concr Res 2001. ¨ zcan F.19:243–7. 1990. [382] Bouzoubaa N. Shpirt MY. Fuel 1999. Klieger P. Yang N. Mehta AK. The University of Leeds. Sirotin G. Fuel 1995. [367] Rougeau P.48(6):51–3.IA13(4):370–3. 1983. Krasnobaeva NV. Laboratory-produced high-volume fly ash blended cements: compressive strength and resistance to the chloride-ion penetration of concrete. RI.76(8):801–5. nçkale.49(2):51–5. Adsorption of surfactants on unburned carbon in fly ash and development of a standardized foam index test. [378] Rixom R. [386] Hill RL. High pressure steam curing of reactivepowder mortars. Elert K. [399] Gray ML. Finseth DH. p. Mechanical properties of high performance concrete made with high calcium high sulfate fly ash. McCormick CJ. Vasiliauskas A. Appl Clay Sci 1996. Preparation of load-bearing building materials from autoclaved phosphogypsum. [391] Ku¨laots I.RILEM 2002. [406] Groppo JG. National Energy Technology Laboratory. p. Min Eng (Littleton. Gao Y.34:135–54. Fuel 2008. p. [411] Domı´nguez EA. et al. 2003. Mater Lett 2004.20:141–7. p. vol. Taastrup. slag and other mineral by-products in concrete. Gao Y-M. Triboelectrostatic separation of fly ash and charge reversal. Constr Build Mater 2009.27(2):193–204. Water Sci Technol 1997. Fuel Process Technol 2002.21:1295–300. Sands W. Illinois: Portland Cement Association. Min Eng (Littleton. [402] Tondu E. Utilization of sewage sludge ashes in the brick and tile industry. Ultra high performance concrete with ultrafine particles other than silica fume.81(6):757–62.507. Brown University Research Foundation. Cem Concr Res 2003. Adv Cem Res 1994. Eshel Y. New York: Van Nostrand Reinhold. Brown University Research Foundation. Unpublished PhD thesis. Dhir RK. Giannopoulou I. In: Proceedings of the workshop on fly ash utilisation: issues and strategies. PhD thesis. SW Washington. Washington. Mater Lett 2003. and frost susceptibility of compacted fly ash. . Effect of synthesis parameters on the mechanical properties of fly ash-based geopolymers. Forecasting and Assessment Council).57:1272–80. 57–62. 41–45. Lukey GC. The characterization of source materials in fly ash-based geopolymers. Federal Highway Administration. Estimation of resource savings due to fly ash utilization in road construction. 2000. Michigan. Ahmaruzzaman / Progress in Energy and Combustion Science 36 (2010) 327–363 [420] Twin Cities Testing and Engineering Laboratory. strength. Investigation of Fly Ash for Use as Compacted Fill’: 1970 Oct. Prospect of utilisation of fly ash in coal mines – a prospective. St. van Deventer JSJ. Compressibility. Utilization of fly ash for remote filling of mine voids. Inc. [421] Lin YK.M. Ash utilisation in NTPC. Perraki T. Paul MN. Resour Conserv Recycl 2006.48:125–40. [427] Panias D. [422] Magnuson MO. DC: US Department of Transportation. p. Patil CB. Bureau of Mines Information Circular 8488. p. Malenka WT.htm.301:246–54.tifac. DC: US Department of the Interior. 1971. 1970. [428] van Jaarsveld JGS. 2000. In: Proceedings of the workshop on fly ash utilisation: issues and strategies.in/ news/flyindia. In: Fly ash a highway construction material. 363 [424] Pan PN. http:// www. 1970.org. [426] TIFAC (Technology Information. University of Michigan. Colloids Surf A Physicochem Eng Aspects 2007. 2005. In: United States Department of the Interior. [425] Kumar S. [423] Mathur AK.