Inter. Res. Jour. In Engr. Sc. & Tech. (IREJEST) Vol. 6 No. 1 Aug.2009 77 Assessment of the Industrial Potentials of Some Nigerian Kaolinitic Clay Deposits MARK, U and ONYEMAOBI, O. O. Department of Materials and Metallurgical Engineering Federal University of Technology, PMB 1526 Owerri __________________________________________________________ ABSTRACT This study considered the mineralogical and chemical analyses of four clay deposits in Abia State, Nigeria namely Ibere, Oboro, Ohiya and Uzuakoli clays, with a view to assessing their potentials for numerous industrial applications. The analyses were done using X-ray Diffractometer (XRD) and Atomic Absorption Spectrophotometer (AAS). It was observed that the clays are predominantly kaolinite. The chemical analysis showed that the silica (SiO2) and alumina (Al2O3) contents of the clays meet the requirements specified for fireclay refractory applications. This is a clear indication that the clays have economic potentials as industrial raw materials for ceramic, paper, paint, fertilizer, and pharmaceutical applications, if beneficiated. Key Words: Assessment, Kaolin, Beneficiation, Industrial Potential INTRODUCTION Clays have been used for centuries for their unique properties in producing building materials and ceramics. In addition to these established uses, clays have become an important part of industrial technology in recent times, taking many roles in manufacturing processes, and are major constituents in products such as plastics and foodstuffs (Velde, 1992). Nigeria is blessed with abundant deposits and widespread distribution of clay minerals, especially kaolinite and bentonite clays. The bulk of kaolinite clay deposits in the country are of sedimentary or residual in origin and are usually associated with granitic rocks (Aliyu, 1996). Data from the Federal Ministry of Solid Minerals Development shows that an estimated reserve of 3 billion tonnes of good kaolinite clay has been identified in many localities in Nigeria (msmdng.com, 2005). The major challenge has been the full characterization of these deposits to ascertain their grade, and their exploitation for national development via mineral processing (Onyemaobi, 2002). The Clay Mineral Kaolinite Kaolin is an important and widely used industrial mineral, which is refined from kaolinite – a naturally occurring mineral of the clay family. Kaolinite (also called china clay or porcelain clay) has an intrinsic white colour, which is often stained brown or grey by impurities derived from the parent rock (Marshal, 1999; Idenyi and Nwajagu, 2003). Clays are formed by the decomposition of complex aluminosilicates (rocks such as granites) by weathering or hydrothermal activity (Hurlburt and Klein, 1977), leaving hydrated aluminosilicates (i.e. clays) of varying compositions and structures, and free silica (Robinson, 1972; Idenyi and Nwajagu, 2003). In the case of kaolinite, the process was represented by (Stocchi, 1990) as: K 2O. Al2O3 .6SiO2 .nH 2O Al2O3 .2 SiO2 .2 H 2O orthoclase / f eldspar H 4 Al2Si2O9 kaolinite K 2O K 2O.SiO2 3SiO2 (n 2) H 2O --- [1] The structural formula of kaolinite can be written as Al2(OH)4.Si2O5 or H4Al2Si2O9 or in terms of oxides as Al2O3.2SiO2.2H2O. The formula shows that the theoretical composition is: SiO2 (46.54%), Al2O3 (39.50%), H2O (13.96%); thus making Mark, U And Onyemaobi, O.O. kaolinite the clay mineral with the highest content of alumina (Al2O3). Kaolinite has a relatively simple twolayer silicate sheet structure consisting of one silica tetrahedral layer [Si2O5]2- which is made electrically neutral by an adjacent aluminium octahedral layer [Al2(OH)4]2+. A crystal of kaolinite consists of series of these double layers of sheets stacked parallel to each other, forming small flat plates typically less than 1µm (0.001mm) in diameter and nearly hexagonal (Callister, 2003). Kaolinite is the commonest of the four aluminosilicate polytypes of the kaolin minerals – the others are dickite, nacrite, and to a lesser extent, halloysite. The variation between members of this family is in the way in which the unit layers are stacked above each other. The names dickite and nacrite indicate a different stacking structure of the basic 7Å kaolinite mineral, while halloysite is a kaolinite with an extra layer of water (H2O) molecules which change its basal spacing to near 10 Å. Regular sequences of one, two, and six kaolin layers are found in kaolinite, dickite and nacrite respectively. Industrial Potentials of Kaolin The uses of clays in general and kaolin in particular depend upon the special properties of the clay particles. Their chemical properties (active internal and external surfaces) are used in many ways, as are their physical properties (grain size and shape, etc). Kaolinite can be used in claypolymer/organic interactions: as is applied in paints and inks (Velde, 1992), where kaolin is employed as an inert colloidal pigment (Brady and Clauser, 1979). Kaolinite also find application as a catalyst to promote organic reactions, such as petroleum cracking or de-polymerization of large organic molecules found in natural hydrocarbons, as demonstrated by Igbokwe and Nwokolo (2005). The grain size and shape of kaolinite is used to advantage in the paper industry, where it is used both as a filling agent and as a coating agent. Printing inks tend to adhere better to kaolin-treated paper surfaces (Velde, 1992; Aliyu, 1996). Both grain size and shape 78 are useful properties in the production of various types of plastic and rubber products, e.g. automobile tires where kaolinite is frequently employed as a filler. Kaolin is a versatile industrial mineral with wide application. It is used as a raw material in papermaking, rubber, plastics, paints, pharmaceuticals, soap, refractories and tiles, cement, fertilizers, textile, insecticides, toothpaste, etc. Medicinally, it is used as adsorbent and in anti-diarrhea formulations (Robinson, 1972; Brady and Clauser, 1979; Aliyu, 1996). Wilson-Eteke, et al (1988) reported how hydrated aluminium sulphate (filter alum) was produced locally at the Federal Superphosphate Fertilizer Company, Kaduna using kaolinite clay from Kankara. The possibility of using this process to produce alumina and by extension, the metal aluminium was also shown. For the wide range of industrial applications, the annual national demand of kaolin would be on the increase. Aliyu (1996) and Adekale (2001) put the national demand at over 150,000 tonnes per annum and over 100,000 tonnes per annum respectively. However, local production was put at 20,000 tonnes per annum. The sad implication of this scenario is that the balance is sourced from abroad to meet the demand of our local industries. Processing of Kaolinite Processing of minerals generally involves beneficiation which implies increasing the percentage composition of the principal components and the removal of contaminants or impurities. The contaminants may be ordinary soil or other associated minerals (Wills, 1997). In the case of kaolinite which is a non-metallic or industrial mineral, the aim of beneficiation is to produce a marketable end product (that meets the requirements/specifications of a target industry) by methods/treatments that do not alter the physical or chemical identity of the mineral (Fuerstenau, 1986). Raw kaolin (as-mined) is crushed and mixed with water to form a slurry. It may be necessary at this stage to add some amounts Inter. Res. Jour. In Engr. Sc. & Tech. (IREJEST) Vol. 6 No. 1 Aug. 2009 of diatomite reagent to decolorize the clay. The slurry is pumped into a vibro-screen to extract foreign particles and impurities, and then into a filter press to dewater the clay. The resulting filter cake of kaolin is dried, milled, classified and bagged according to the requirements of the target industry (Reed, 1988; Aliyu, 1996). Figure 1 is a typical flow diagram for kaolin processing. The equipment required for the industrial processing of kaolin include plungers, hydrocyclones, sieves, filter press, dryers, calciners, hammer mills, pumps, conditioners, floatation machines, and weighing/bagging machines (Reed, 1988; Adekale, 2001). The present study considers the mineralogical and chemical characterization of Ibere, Oboro, Ohiya and Uzuakoli clay deposits in Abia State. MATERIALS AND METHODS Clay samples were collected from four different deposits in Abia State namely: Umulu/Ngwugwo-Ibere [5O26I N, 7O35I E], Ekebedi/Ogbuebule-Oboro [5O22I N, 7O33I E] both in Ikwuano LGA, Ohiya [5O30I N, 7O26I E] in Umuahia South and AgbozuUzuakoli [5O38I N, 7O34I E] in Bende LGA. The clays will be designated as Ibere, Oboro, Ohiya and Uzuakoli respectively, for identification purposes. Figure 2 is a map of Abia State showing the location of these deposits as well as other clay deposits in the State. The raw clay was crushed and mixed thoroughly to achieve homogeneity. Samples were taken from each of the clays and labeled appropriately for analyses. Mineralogical Analysis The mineralogical constituents (e.g. amount of free silica/quartz, kaolinite or any other associated mineral) of the four clays were determined at Alfa Research Laboratories Ltd. in Lagos. Mineralogical composition of Ibere, Oboro, Ohiya and Uzuakoli clay samples were determined using X-ray techniques. Qualitative and quantitative mineralogical phase analyses 79 were performed using the X-ray Diffractometer (XRD) - Phillips PW 3710, and Cu Kα-radiation (λ = 1.5418Ǻ). X-ray patterns were collected on powdered samples in θ/2θ mode with a starting analysis angle of 5 degrees and a finishing analysis angle of 70 degrees; with a data interval of 0.01 degree. Chemical Analysis Chemical analysis of the clay materials was carried out using an Atomic Absorption Spectrophotometer (AAS) also at Alfa Research Laboratories Ltd. Chemically combined water (constitutional H2O) was determined using loss on ignition (LOI) test. RESULTS AND DISCUSSION Mineral Constituents The mineral analyses as shown in Table 1 and Figure 3 confirm that the clays are predominantly kaolinite with Ibere assaying 67%, Oboro (53%), Ohiya (76%) and Uzuakoli (62%). Other minerals identified are free silica (quartz), illite, chlorite, montmorillonite and feldspar. The total clay minerals content was 81.2% for Ibere, 60.8% for Oboro, 89.1% for Ohiya, and 82% in the case of Uzuakoli. However, the non-clay minerals detected include free silica (SiO2) and traces of calcite (CaCO3) and haematite (Fe2O3). The XRD patterns (traces of Intensity versus 2θ degrees) are shown in Figures 4, 5, 6 and 7 for Ibere, Oboro, Ohiya and Uzuakoli clays respectively. All clay minerals are known to contain alumina (Al2O3) and silica (SiO2); and this is also true of feldspars which decompose to form clays by hydrothermal activities. From the results of the mineralogical analyses, it therefore follows that if these clays are beneficiated, the alumina content and other associated oxides can be adjusted to meet the needs of various industries (Table 2), while reducing the free silica content. Chemical Composition The chemical compositions of the four clays analyzed are given in Table 2 along with the compositional specifications of kaolin for a number of industrial applications. Mark, U And Onyemaobi, O.O. Chemically, all the clays (in their raw condition) qualify as fireclay refractory and ceramics raw materials, with the possible exception of Oboro which has the lowest alumina content of 19.05%. With beneficiation, the chemical quality will be improved to meet the specifications given by Aliyu (1996) and Emofuriefa, et al (1992) for the industrial applications highlighted in Table 2 as well as for other uses. CONCLUSION The mineralogical and chemical characterization of Ibere, Oboro, Ohiya and Uzuakoli clays in Abia State show that they are kaolinitic and can be used as fireclay refractory raw materials for furnace and kiln lining. The chemical composition shows that the clays are potential raw materials for the ceramics, paper, paints, pharmaceutical, fertilizer and allied industries if beneficiated. Kaolin was listed among the industrial raw materials that must be immediately deleted from the Nation’s import list (Aliyu, 1995) if the country must achieve the much needed resource-based industrialization policy. It is therefore recommended that: 1. Nigeria should intensify efforts to completely stop the import-substitution industrialization strategy as far as kaolin is concerned. 2. Favourable environment should be provided for local and foreign investors in raw materials (kaolinite inclusive) development. REFERENCES ADEKALE, O. A (2001) Sustainable Development of National Raw Materials, Proc. of the Nigerian Metallurgical Society, the 18th Annual Conf. Pp. 54-61 ALIYU, A (1995) Industrialization in Nigeria: An Appraisal. Lagos: Dilli’s Ventures Ltd. 80 ALIYU, A (1996) Potentials of the Solid Minerals Industry in Nigeria Abuja: RMRDC. pp. 1-40, 63-83, 164-172 BRADY, G. S and CLAUSER, H. R (eds.) (1979) Materials Handbook New York: McGraw-Hill. Pp. 410-411. CALLISTER, JR. W. D (2003) Materials Science and Engineering: An Introduction, Sixth Edition New York: John Wiley. pp. 384-410, 425-443 EMOFURIEFA, W.O; KAYODE, A.A and COKER, S.A (1992) Mineralogy, Geochemistry and Economic Evaluation of the Kaolin Deposits near Ubulu-Uku, Awo-Omama and Uruala in Southern Nigeria. Journal of Mining and Geology, vol.28, No.2, pp 211- 220 FUERSTENAU, D. W (1986) Mineral Processing In BEVER, M. B. (ed.), Encyclopedia of Materials Science and Engineering, vol.4 Oxford: Pergamon Press/The MIT Press. Pp. 3062-3070. HURLBURT, JR. C.S and KLEIN, C (1977) Manual of Mineralogy, 19th Edition New York: John Wiley and Sons, pp.1, 49 IDENYI, N.E. and NWAJAGU, C. O. (2003) Non-metallic Materials Technology, Enugu: Olicon Publications, pp. 1-47. IGBOKWE, P. K. and NWOKOLO,S.O (2005) Catalytic Esterification of Stearic Acid using a Local Kaolinite Clay Mineral Nigerian Journal of Engineering Research and Development, vol. 4, No. 1, pp. 22-27 MARSHAL, K. M. W. (1991) The “Valencia White” Clay: An Assured Raw Material for Ceramics . The Geological Society of Trinidad & Tobago. Available online @ http://www.gstt.org/publications/news/ne wsletters/15/white%20sands.htm MSMDNG.COM (2005) Federal Ministry of Solid Minerals Development Profile of Solid Minerals Deposits in Nigeria Available online @ http://www.msmdng.com/ NNANEDU, C.E (1989) Characterization of Minerals and Materials by X-ray Inter. Res. Jour. In Engr. Sc. & Tech. (IREJEST) Vol. 6 No. 1 Aug. 2009 and Other Methods Lagos: Marathon Academic Publishing Co. 127pp. ONYEMAOBI, O. O (2002) Mineral Resources Exploitation, Processing and Utilization – A Sine Qua Non for Nigeria’s Metallurgical Industrial Development Inaugural Lecture Series 5 of FUTO, Owerri: FUTO Press. 48pp REED, J. S. (1988). Introduction to the Principles of Ceramic Processing New York: John Wiley. ROBINSON, H. (1972). Geography for Business Studies, Second Edition London: Macdonald & Evans Ltd. pp.245-249 STOCCHI, E (1990). Industrial Chemistry Volume 1 [Translated by K.A.K. LOTT and E.L. SHORT] London: Ellis Horwood. Pp.551-560 VELDE, B (1992). Introduction to Clay Minerals-Chemistry, Origins, Uses and Environmental Significance London: Chapman and Hall, pp. 1-3, 12, 13, 4148, 68, 79, 80, 164-178. WILSON-ITEKE, H.K.E; OGUNGBEMI, J.T; KANTI, A and AKANBI, C. (1988) Hydrated Aluminium Sulphate (Filter Alum): Some Notes on Pilot Plant Raw kaolin 81 Work at Federal Superphosphate Fertilizer Company. Journal of the Nigerian Society of Chemical Engineers, 7(2), pp.328-336 WILLS, B. A (1997) Mineral Processing Technology, Sixth Edition Boston: Butterworth-Heinemann Crushing Slurry Water De-gritting Leaching Chemical Screening Dewatering Drying Milling Calcining Classifying Pulverizing Packaging Figure 1: Flow Diagram for Kaolin Processing Mark, U And Onyemaobi, O.O. 82 Table 1: Mineralogical Composition of Clay Samples (XRD) Constituents (%) Ibere Oboro Ohiya Kaolinite1 67 53 76 Free Quartz 13 32 6 2 Illite 4.6 2.5 3.7 Chlorite3 6 5.3 2.4 Montmorillonite4 3.6 7 Feldspar 2 5 2 Clay Content [1+2+3+4] 81.2 60.8 89.1 Uzuakoli 62 11 3 17 4 82 80 70 60 Composition (Weight %) 50 40 30 20 Kaolinite Quartz Illite 10 Chlorite Montmorillonite Feldspar 0 Ibere Oboro Ohiya Uzuakoli Sample Identification Figure 3: Mineral Constituents of Clay Samples Inter. Res. Jour. In Engr. Sc. & Tech. (IREJEST) Vol. 6 No. 1 Aug. 2009 83 Mark, U And Onyemaobi, O.O. 84 Table 2: Chemical Composition of the Clays Compared with Specifications for Some Industrial Needs Composition (%) Ibere Oboro Ohiya Uzuakoli SiO2 52.06 60.21 48.23 53.65 Al2O3 27.87 19.05 29.45 26.42 Fe2O3 3.25 3.78 3.58 2.50 TiO3 CaO 0.34 0.30 0.22 0.28 MgO 1.43 1.50 1.49 1.52 Na2O 0.38 0.42 0.29 0.45 K2O 2.92 2.16 2.56 2.78 LOI 9.3 10.2 13.4 12.2 After Aliyu (1996) Ceramics Paper (as coating agent) Paper (as filling agent) Pharmaceutical 48.00 47.80 48.70 48.00 37.00 37.00 36.00 36.00 0.60 0.58 0.82 0.10 0.03 0.03 0.05 0.02 0.10 0.40 0.60 0.10 0.30 0.16 0.25 0.20 0.10 0.10 0.10 0.10 1.60 1.10 2.10 1.10 12.40 13.10 12.01 11.90 After Emofuriefa, et al (1992) Ceramics 67.50 45.90 – 45.80 47.9 – 45.3 46.07 51.00 – 70.00 26.50 33.50 – 36.10 37.9 – 38.4 38.07 25.00 – 44.00 0.50 – 1.20 0.30 – 0.60 13.2 – 13.4 0.33 0.50 – 2.40 0.18 – 0.30 0.00 – 0.50 0.03 – 0.25 0.38 0.10 – 0.20 0.10 – 0.19 1.40 – 5.60 (Other Oxides) <4.90 1.95 - 2.20 (Other Oxides) 1.20 (Other Oxides) 0.80 – 3.50 (Other Oxides) Paper Paints Fertilizer Refractory Bricks 0.20 – 0.30 0.01 0.20 – 0.70
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