W9 Issue 22 Instruction Manual

Ion Exchange ApparatusInstruction Manual W9 ISSUE 22 August 2011 Table of Contents Copyright and Trademarks ...................................................................................... 1 General Overview ....................................................................................................... 2 Equipment Diagrams................................................................................................... 3 Important Safety Information....................................................................................... 4 Introduction.............................................................................................................. 4 Electrical Safety....................................................................................................... 4 Wet Environment ..................................................................................................... 4 High Pressure.......................................................................................................... 5 Heavy Equipment .................................................................................................... 5 Chemical Safety ...................................................................................................... 5 Water Borne Hazards .............................................................................................. 5 Description .................................................................................................................. 7 Overview.................................................................................................................. 7 Installation ................................................................................................................... 9 Advisory................................................................................................................... 9 Electrical Supply ...................................................................................................... 9 Installing the Equipment ........................................................................................ 10 Commissioning ...................................................................................................... 11 Operation .................................................................................................................. 13 Operating the Equipment....................................................................................... 13 Operation of the Conductivity Meter ...................................................................... 13 Equipment Specifications.......................................................................................... 14 Overall Dimensions ............................................................................................... 14 Electromagnetic Compatibility ............................................................................... 14 Equipment Location............................................................................................... 14 Environmental Conditions...................................................................................... 14 Routine Maintenance ................................................................................................ 15 Responsibility ........................................................................................................ 15 General.................................................................................................................. 15 ii Table of Contents Laboratory Teaching Exercises................................................................................. 16 Index to Exercises ................................................................................................. 16 Water Softening Theory......................................................................................... 16 Regeneration Theory............................................................................................. 16 Demineralisation Theory........................................................................................ 17 Resin Volume and Density .................................................................................... 18 Exchange Capacity................................................................................................ 18 Data Sheet I........................................................................................................... 18 Data Sheet II.......................................................................................................... 20 Data Sheet III......................................................................................................... 23 Data Sheet IV ........................................................................................................ 23 Exercise A ................................................................................................................. 25 Exercise B ................................................................................................................. 27 Exercise C................................................................................................................. 29 Exercise D................................................................................................................. 32 Contact Details for Further Information ..................................................................... 33 iii . This document must not be used for any purpose other than that for which it is supplied and its contents must not be reproduced. adapted. All rights reserved. 1 .uk Fax: +44 (0) 1425 470916 Copyright and Trademarks Copyright © 2011 Armfield Limited. translated or disclosed to any third party.Disclaimer This document and all the information contained within it is proprietary to Armfield Limited. Any technical documentation made available by Armfield Limited is the copyright work of Armfield Limited and wholly owned by Armfield Limited. please contact the Armfield Customer Support helpdesk (Monday to Thursday: 0830 – 1730 and Friday: 0830 . Contact details are as follows: United Kingdom (0) 1425 478781 (calls charged at local rate) International +44 (0) 1425 478781 (international rates apply) Email: [email protected] UK time). published. Should you have any queries or comments. without the prior written permission of Armfield Limited. Brands and product names mentioned in this manual may be trademarks or registered trademarks of their respective companies and are hereby acknowledged.co. modified. in whole or in part. The process is reversible. 2 . Consulting Chemist to the Royal Agricultural Society in England.S.e. They can be made as either cation. phenol-formaldehyde resins by Adams and Holmes in 1935 and polymerization resins based on styrene. He found that many forms of ion exchange occurred in various soils. Thompson observed that ammonium sulphate fertilizer applied to soil emerged as a solution of calcium sulphate. regenerating it with sodium chloride.T.General Overview Ion exchange is a natural process in which ions held on the surface of a solid displace other ions. to restore Na+ ions on the surface. reach equilibrium. Way was able to prepare artificial aluminosilicates with ion exchange properties. from a solution in contact with the solid. while those originally on the surface go into solution. The first commercial ion-exchange demineralization plant was installed in 1937 at a brewery in Guildford. When equilibrium is reached. by d’Alelio in 1944. usually sodium chloride. Since then. The first practical use of ion exchange in water treatment was by the German R. In 1850-54 the process was closely studied by J. Besides these uses in the treatment of water supplies. when he used a synthetic material to soften water.M. History The phenomenon of ion exchange was discovered in the middle of the nineteenth century. ion exchange processes are also widely employed in industry. known as zeolites. when H. i.the process of demineralisation. By the use of suitable ion exchange materials in two or more stages it is possible to remove all dissolved salts from solution . and that the materials involved were complex hydrated aluminosilicates. with the introduction of sulphonated coals by Liebknicht in 1934. The displaced ions become attached (ie. This process of exchange continues until the relative concentration of the two types of ions. The simplest example of practical ion exchange is in the softening of water. The ion exchange apparatus described in this manual enables both softening and demineralisation to be studied. when the exchange capacity of the material is exhausted. Way.or anion-exchangers and by using both types in series demineralization is possible. when Ca2+ ions in the water (causing hardness) are exchanged for Na+ ions on the exchange material. Gans in 1905. it can be regenerated by applying a concentrated solution of a sodium salt. England. on the surface and in solution. the direction of the exchange depending upon these relative concentrations. The properties sought in the newer synthetic materials include physical and chemical stability as well as greatly increased exchange capacities. the range of synthetic materials has been greatly extended. of similar and equivalent electrical charge. held by electrostatic attraction) to the surface. Equipment Diagrams Figure 1: W9 Ion Exchange Apparatus 3 . During use it is possible that there will be some spillage and splashing. It must be connected to a supply of the same frequency and voltage as marked on the equipment or the mains lead. mishandled or badly maintained. dangers exist if the equipment is misused. If through misuse or accident the equipment becomes electrically dangerous. Failure to trip means that the operator is not protected and the equipment must be checked and repaired by a competent electrician before it is used. At least once each month. will not cause injury to that person. and should wear appropriate clothing and non-slip footwear.    All users should be made aware that they may be splashed while operating the equipment. the unit incorporates a Residual Current Device (RCD). If requested then Armfield can supply a typical set of standard laboratory safety rules. The circuit breaker MUST trip when the button is pressed. To give increased operator protection. the RCD will switch off the electrical supply and reduce the severity of any electric shock received by an operator to a level which. alternatively called an Earth Leakage Circuit Breaker. as an integral part of this equipment. The equipment must not be operated with any of the panels removed. Electrical devices in the vicinity of the equipment must be suitable for use in wet environments or be properly protected from wetting. but these are guidelines only and should be modified as required. and that the apparatus is operated in accordance with those regulations. Wet Environment The storage tanks on the equipment require filling and draining in use. under normal circumstances. As with any piece of sophisticated equipment. 4 . Electrical Safety The equipment described in this Instruction Manual operates from a mains voltage electrical supply. operated and maintained in accordance with the instructions in this manual.Important Safety Information Introduction All practical work areas and laboratories should be covered by local safety regulations which must be followed at all times. check that the RCD is operating correctly by pressing the TEST button. ‘Wet Floor’ warnings should be displayed where appropriate. It is the responsibility of the owner to ensure that all users are made aware of relevant local regulations. Your W9 Ion Exchange Apparatus has been designed to be safe in use when installed. Supervision of users should be provided whenever appropriate. consult a qualified electrician or contact Armfield. If in doubt. rust. Only use chemicals specified in the equipment manuals and in the concentrations recommended. the microscopic bacterium called Legionella pneumophila will feed on any scale. which under certain conditions can create a health hazard due to infection by harmful micro-organisms. Ensure that the selector valves are set correctly to configure the flow through the apparatus before switching on the feed pump.  The feed pump can produce more flow that is required by the process so it is important to adjust the bypass on the feed pump to allow liquid to return to the feed tank and avoid excessive pressure in the pipework. Chemical Safety Details of the chemicals intended for use with this equipment are given in the Operational Procedures section. but it serves as a useful example of the need for cleanliness. 5 . Any water containing this bacterium which is sprayed or splashed creating air-borne droplets can produce a form of pneumonia called Legionnaires Disease which is potentially fatal. Prepare chemicals and operate the equipment in well ventilated areas.  Heavy Equipment This apparatus is heavy.     It is the user’s responsibility to handle chemicals safely. the following precautions must be observed:  Any water contained within the product must not be allowed to stagnate. as described in the Installation section of the manual. health and safety and other issues. The setting of the clip on the bypass tubing is described in the Commissioning section. It is important that these guidelines are adhered to. This will avoid excessive pressure in the system. Follow local regulations regarding chemical storage and disposal. Legionella is not the only harmful micro-organism which can infect water. For example. Under the COSHH regulations. the water must be changed regularly. Water Borne Hazards The equipment described in this instruction manual involves the use of water.  The apparatus should be placed in a location that is sufficiently strong to support its weight.Important Safety Information High Pressure This apparatus is designed to operate with internal pressures greater than that of the surrounding atmosphere. algae or sludge in water and will breed rapidly if the temperature of water is between 20 and 45°C. ie. Chemicals purchased by the user are normally supplied with a COSHH data sheet which provides information on safe handling. scale or algae on which micro-organisms can feed must be removed regularly.Armfield Instruction Manual   Any rust. If this is not practicable then the water should be disinfected if it is safe and appropriate to do so.Health and Safety Series booklet HS (G) 70. A scheme should be prepared for preventing or controlling the risk incorporating all of the actions listed above. sludge. 6 . Where practicable the water should be maintained at a temperature below 20°C.e. i. the equipment must be cleaned regularly. Note that other hazards may exist in the handling of biocides used to disinfect the water.  Further details on preventing infection are contained in the publication “The Control of Legionellosis including Legionnaires Disease” . This valve must not be fully closed to avoid excess pressure in the system. Overview All numerical references relate to Figure 1. After passing through the columns the treated water. The liquids are selected by lifting and traversing the sliding tube arrangement (13) at the front of the sump tank. a backboard (1) incorporating the main process components and a sump tank arrangement (14) for storing and pumping the associated liquids. The flexible tube from the pump outlet to the selector assembly returns excess liquid to the feed tank for reuse. to be adjusted as required. regenerating solution etc. This allows the quality of the water emerging from the ion exchange column(s) to be monitored. The equipment includes a battery operated digital conductivity meter (19) that is connected to an inline sensor (18) in the return line (17) to the effluent tank. Also refer to the schematic diagram showing the valve positions in Data Sheet III. The pump is operated using the electrical switch (4) at the right hand side of the process backboard and is connected via an in-line electrical connector (16). 7 . A flow control valve (10) at the base of the flowmeter allows the flow of water. Ion exchange takes place inside two vertical transparent columns (5 & 6). exhausted regenerating solution or wash water is fed to an effluent storage tank at the rear of the sump tank arrangement via flexible tube (11) from the top of the columns or flexible tube (17) from the bottom of the columns. mounted on the backboard via manifolds at the top (7) and bottom (2). simply by opening the appropriate lever operated valve. Screwed connectors fitted with ‘O’ ring seals (3) allow the columns to be removed for cleaning or changing the type of exchange resin. The manifolds at the top (7) and bottom (2) of the columns are fitted with lever operated isolating valves which allow the flow to be directed through one or both columns. In use the left hand column (5) contains Cation exchange resin (golden coloured granules) and the right hand column (6) contains Anion exchange resin (white coloured granules). to the top of the Cation column or to the base of both columns as required by the process. which is designed for experiments on both water softening and demineralisation. to suit the process requirements. in either direction. A distribution manifold (8) above the flowmeter allows the pumped liquid to be supplied to the top of the Anion column. The apparatus. The liquids to be passed through the exchange columns are stored in the sump tank arrangement (14) to the left of the apparatus and supplied via a pump (12) and flowmeter (9). Lever operated valves (V4.Description Where necessary. V10 or V16) allow samples of water to be collected for analysis if required. This tank incorporates a lever operated valve (15) to facilitate draining. of approximately 16mm internal diameter. is supplied split into two major components. refer to the drawings in the Equipment Diagrams section. An adjustable pinch valve (19) on the bypass tube is adjusted to give the correct flow conditions. b. Regeneration solutions (followed by distilled or demineralised water for flushing). which will pass downwards through the Cation exchanger only. which are stored in separate tanks. 8 . d. Water to be softened. Water (preferably distilled or demineralised) which will pass upwards through either column to flush out any sediment and to release any air trapped in the resin. c. Water to be demineralised. and will pass downwards through either the Cation or the Anion exchange column. which will pass downwards through the Cation exchanger and then upwards through the Anion exchanger.Armfield Instruction Manual The various processes involved in the experiments are as follows: a. it must be unpacked. assembled and installed as described in the steps that follow. The transformer should be sited adjacent to the 120V mains outlet socket in the laboratory. Electrical Supply Electrical supply for version W9-A The equipment requires connection to a single phase. The standard electrical supply for this equipment is 120V. Connection should be made to the supply cable as follows: GREEN/YELLOW BROWN BLUE Maximum Current EARTH LIVE (HOT) NEUTRAL . The standard electrical supply for this equipment is 220-240V. 60Hz. Check that the voltage and frequency of the electrical supply agree with the label attached to the supply cable on the equipment.Installation Advisory Before operating the equipment. Connection should be made to the supply cable as follows: GREEN/YELLOW BROWN BLUE Maximum Current EARTH LIVE (HOT) NEUTRAL . Safe use of the equipment depends on following the correct installation procedure. the mains lead from the W9-G can be connected directly to the 220V electrical socket in the laboratory (stepup transformer not used).1 AMP Note: Version W9-B consists of a W9-G with a loose transformer to step-up the 120V supply to 220V to suit the equipment. fused electrical supply. Installation may be completed using a basic tool kit. Check that the voltage and frequency of the electrical supply agree with the label attached to the supply cable on the equipment. The mains lead from the W9-G is simply plugged into the 220V outlet socket on the front of the transformer. 9 .1 AMP Electrical supply for version W9-B The equipment requires connection to a single phase. 50Hz. Where a 220V electrical supply is available in the laboratory. in a dry location. fused electrical supply. The tube which projects furthest into the tank should be connected to the side connection on the pump inlet (see Connection 1). fused electrical supply. Connection 1 Connection 2 10 . The standard electrical supply for this equipment is 220V. Connection should be made to the supply cable as follows: GREEN/YELLOW BROWN BLUE Maximum Current EARTH LIVE (HOT) NEUTRAL 1 AMP Installing the Equipment All numerical references relate to Figure 1. The tube with the shortest projection should be connected to one side of the Tconnector on the pump outlet (see Connection 2). with regard to the service connections listed in Electrical Supply above. The diaphragm pump (12) is removed to avoid damage during transit and should be attached to the mounting plate on top of the sump tank assembly (14) using the fixings provided.Armfield Instruction Manual Electrical supply for version W9-G The equipment requires connection to a single phase. Locate the sump tank arrangement to the left hand side of the process backboard. 60Hz. The easiest method may be to insert the screws from underneath. with the nuts positioned on the outside of the tank assembly. Position the equipment in the desired location on a firm level bench. Check that the voltage and frequency of the electrical supply agree with the label attached to the supply cable on the equipment. Connect the sliding tube arrangement (13) at the front of the tank to the pump (12) using the flexible tubing supplied. 6. 1. Connect the equipment to the electrical supply and confirm satisfactory operation of the RCD by pressing the TEST button (Refer to the notes on Electrical Safety). Install the battery in the conductivity meter following the instructions supplied with the conductivity meter. 11 . Open the flow control valve at the base of the flowmeter and set the valve to approximately mid-position. Also refer to the schematic diagram showing the valve positions in Data Sheet III. 5. 3. It is suggested that clean tap water is used for initial testing of the equipment. Check all flexible connections are secure and all valves are closed. Reset the RCD. 7.Installation Connect the inlet of the control valve (10) at the bottom of the flowmeter (9) to the outlet of the pump using the flexible tubing supplied. 4. Connect the two parts of the inline electrical connector (16) between the pump (12) and the rear of electrical switch (4) on the process backboard. 2. Connect the two flexible effluent return tubes (11) from the top manifold and (17) from the inline conductivity electrode to the tappings on the side of the tank assembly. Ensure the equipment has been assembled in accordance with the instructions in the Assembly section above. Commissioning All numerical references refer to Figure 1 in the Equipment Diagrams. Connect the lead from the conductivity electrode to the socket at the top of the conductivity meter. Lift the selector tube (13) and confirm that it will traverse along to each of the four compartments. Fill the four supply tanks at the front of the sump tank arrangement (14) with clean tap water (l litre approximately). Ensure that the drain valve (15) on the effluent tank is closed. The equipment is ready for commissioning. Check that water flows from valve V16. Open valves V1 and V15. 11. 18. Connect a flexible tube to sample valve V16 or place a container beneath the valve. 14.Armfield Instruction Manual 8. Open valves V2. V13 and V16. When the bypass is correctly adjusted. Move the selector (13) to tank C (Test Water). 17. Close both valves. check that water returns to the sump tank after flowing downwards through the Cation column (6) then downwards through Anion column (5). open valves V3 and V6 then switch on the pump and allow the pump to prime. 12 . Check the equipment for any leaks. Open valves V2 and V10. Check that water flows from valve V10. 13. V13 and V15. 16. Switch on the conductivity meter (9) by pressing the Power button. If the bypass is too far open then oscillation of the flow will be visible in the flowmeter. Close the valve. Open valves V2 and V12 and check that water returns to the sump tank after flowing downwards through the Cation column (6). 19. If the bypass is closed too far then the system may become over pressurised which could result in damage to the system and leakage of fluid. Gradually close the Hoffman clip on the flexible bypass tube until the flow through the flowmeter becomes steady. Water will flow through the bypass and return to tank C. Open the drain valve (15) on the effluent tank and ensure that it operates correctly. Connect the lead from the inline conductivity sensor to the socket marked INPUT at the top of the conductivity meter. Close both valves. 10. Close both valves. Close all three valves. Open valves V2. 15. Check that the meter indicates the conductivity and temperature of the water (a series of dashes in the display indicates that the selected range is not correct – move the range selector switch until the conductivity of the water is indicated). Open valves V3 and V9. Close both valves. indicated by a steady reading on the float. 12. If necessary adjust the flow control valve to give a reading on the flowmeter while adjusting the bypass. Close all three valves. Open valves V3 and V9 then check that water returns to the sump tank after flowing upwards through the Cation column (6). Close both valves. check that water returns to the sump tank after flowing upwards through the Anion column (5). 9. check that water returns to the sump tank after flowing downwards through the Anion column (5). excess water will be returned to tank C when the flow control valve is closed avoiding over pressurisation of the pump and pipework. Connect a flexible tube to sample valve V10 or place a container beneath the valve. in units of micro Siemens (μS) or milli Siemens (mS) depending on the position of the range switch. For further information on the conductivity meter refer to the instruction leaflet supplied with the equipment. 13 . The meter gives a direct reading of conductivity. Dashes in the display indicate that the range switch is in the wrong position and should be adjusted to suit. The lead from the inline sensor is connected to the socket marked INPUT at the top of the conductivity meter. An inline conductivity sensor is installed at the outlet from the bottom manifold so that it can monitor the conductivity of the water following the ion exchange process. The conductivity meter is powered by an internal 9 volt PP3 Alkaline battery. Operation of the Conductivity Meter The conductivity meter is supplied separately and is designed to sit on the bench top alongside the equipment. press the POWER button and adjust the position of the range switch until the meter indicates the Conductivity and Temperature.Operation Operating the Equipment Refer to the Laboratory Teaching Exercises for details on operating the equipment. To operate the conductivity meter. corrected for temperature. a. Transient over-voltages typically present on the MAINS supply.1. Maximum relative humidity 80% for temperatures up to 31°C.1m Depth . Temperature 5°C to 40°C. Four metres of supply cable are provided with the equipment. Equipment Location The equipment is fully self-contained and is designed to be bench mounted. b. Typical of an office or laboratory environment. Note: The normal level of transient over-voltages is impulse withstand (overvoltage) category II of IEC 60364-4-443. dilute sodium hydroxide and dilute sodium chloride). Operation outside of these conditions may result reduced performance. Normally only nonconductive pollution occurs. f. The equipment requires connection to a single phase. 14 .0. Temporary conductivity caused by condensation is to be expected. laboratory or similar such place invalidates conformity with the protection requirements of the Electromagnetic Compatibility Directive (89/336/EEC) and could lead to prosecution. Mains supply voltage fluctuations up to ±10% of the nominal voltage. d. A source of clean water will be required for filling the sump tank and a suitable drain for disposing of effluent from the equipment (involving dilute hydrochloric acid. Refer to Electrical Supply in the Installation section. decreasing linearly to 50% relative humidity at 40°C. g. fused electrical supply.45m Electromagnetic Compatibility This apparatus is classified as Education and Training Equipment under the Electromagnetic Compatibility (Amendment) Regulations 1994. Environmental Conditions This equipment has been designed for operation in the following environmental conditions. Use of the apparatus outside the classroom. Pollution degree 2. e.Equipment Specifications Overall Dimensions Height . damage to the equipment or hazard to the operator. Indoor use. c. Altitude up to 2000m.0.9m Width . A mains electrical supply is required to operate this product. The sensor can be totally removed by passing the plug through the opening. 15 . However. The sensor body is sealed into the housing using an ‘O’ ring. This should be lubricated with soapy water before reinserting the sensor into the inline housing after cleaning. General Disconnect the equipment from the electrical supply when not in use. The conductivity sensor is usually cleaned adequately by passing clean water through the system after use. Push the sensor fully into the housing then replace the large sealing plug. unscrew the large sealing plug on the side of the housing (opposite the lead from the sensor) then push the sensor through the opening. Clean the storage tanks with distilled or deionised water and flush both columns if different solutions and resins are to be used. To remove the sensor. Drain any effluent contained in the sump tank after every experiment to a suitable laboratory drain.Routine Maintenance Responsibility To preserve the life and efficient operation of the equipment it is important that the equipment is properly maintained. the sensor can be removed from the inline housing if manual cleaning of the electrodes becomes necessary. Regular maintenance of the equipment is the responsibility of the end user and must be performed by qualified personnel who understand the operation of the equipment. There is thus. a zone of active exchange which moves down the column until the resin at all depths becomes exhausted.17g NaCl for regeneration (equivalent weights: CaCO3 50. NaCl 58. Softening can be carried out as a batch process by stirring a suspension of the resin in the water for a period until equilibrium. the emerging water begins to show an increasing hardness.5). When the zone of active exchange reaches the bottom of the column. The position at an intermediate stage can be illustrated as shown below. one millequivalent of NaCl is required for regeneration. when it becomes necessary to regenerate the resin with a strong sodium chloride solution. it is more convenient to operate a continuous flow process by passing the water slowly downwards through a column of resin beads. This resin has a strong affinity for calcium and magnesium ions. 16 . The exchange reaction takes place rapidly enough for the upper layers of the bed to approach exhaustion before the lower layers being able to exchange ions. Regeneration Theory Theoretically. is reached.0. 1g of hardness as CaCO3 removed requires 1. However. and will also remove ferrous ions after the more or less complete removal of calcium and magnesium.Laboratory Teaching Exercises Index to Exercises Exercise A Exercise B Exercise C Exercise D Water Softening Theory The most usual ion exchange material employed in water softening is a sulphonated styrene-based resin. This is the breakthrough point. supplied by the makers in the sodium form. or an acceptable level of hardness. ie. for every millequivalent (meq) of hardness as CaCO3 removed from the water under treatment. a strongly basic anion exchanger must be used as the final stage. Larger quantities of NaCl are therefore used. Water to be treated by ion exchange must be free of suspended solids which would block the passage-ways. but it is uneconomic to operate at such a rate that this capacity is fully used in softening. The practical operation of an ionexchange bed is therefore a compromise in which the regeneration efficiency and the column utilisation are both in the region of 50%. the two resins are re-mixed by compressed air. The rate of flow of water through the bed in softening is usually not more than 40ml/min per cm2 of surface area of bed. This is then passed through an anion exchanger in the hydroxyl ion form.(due to dissolved carbon dioxide) and H3SiO4. Demineralisation Theory The removal of all dissolved salts from water can be achieved by using a two-stage ion exchange process. which with the H+ ions. when cations in the water are replaced by H+ ions.Laboratory Teaching Exercises In practice it is not possible to achieve complete regeneration with this quantity of NaCl. This process can reduce total dissolved solids to below 1mg/l. when the acid ions are replaced by OH. generally twice or more the theoretical amount. distilled or demineralised water is passed through the bed to wash out any remaining regenerant. After regeneration. To remove fine solids which may get into the bed. The regeneration efficiency is thus around 50%. since this would require an unacceptable long contact period. and a degassing tower to release CO2 from solution. The water repeatedly comes in contact with the two resins alternately. It is often sufficient to use a weakly basic anion exchanger. produce water. the anion resin being of lower density and therefore carried to the top. and is ultimately of very high purity. they are first stratified with an upward flow of water. For a higher quality product water. and vice versa. but it is generally more economical to precede this with a weakly basic anion exchanger of high exchange capacity to remove the bulk of the anions.ions. The strongly basic resin is then required only to remove silica and any residuals of other anions which may still be present. Regeneration rates are about one tenth of this. In other words. giving a solution of acids. The water is first passed through a strong cation exchanger working on the hydrogen ion cycle.(due to dissolved silica). and to release any air pockets. To enable the two resins to be regenerated with sulphuric acid and sodium hydroxide respectively. Demineralisation can also be performed in a single stage by using a mixed bed of strong cation and anion exchangers. a high regeneration efficiency is associated with a low degree of column utilisation. the column is backwashed periodically by an upward flow of water which fluidises the bed and agitates the resin beads. A high level of regeneration gives a resin with a high exchange capacity approaching its theoretical. reduce flow rates and interfere with the exchange process. 17 . After regeneration. which will remove all anions except HCO3. 7 and 0. The density of a resin can also be given as the true density. It is also important to wet a resin thoroughly. The theoretical exchange capacity may be defined as the number of exchangeable ions which it contains per unit mass or volume. i. mass per unit volume of the bed. nor is it economic to regenerate fully. and meq/l of wet resin bed. mass per unit volume of the beads alone. For typical resins the true wet density is usually between 1. It is expressed in various units. including the voids.Armfield Instruction Manual Resin Volume and Density When dry ion-exchange resins are immersed in water the beads swell as a result of hydration of the fixed and counter-ions (i. In practice it is not feasible to provide a long enough contact period for complete equilibrium to be attained.e. of which the most useful are probably millequivalents (meq) of exchanged ions per gram of dry resin. The inside diameter of both exchange columns is approximately 16mm. in order to avoid damage as a result of the swelling.3 g/cm3. or as the apparent density. For accurate results it is suggested that the actual inside diameter of both columns is measured and recorded before filling with exchange resin. and the apparent wet density between 0.e. the usual unit being kg CaCO3 /m3 of wet resin bed. i.8 g/cm3. In the softening of water it is also common practice to express the exchange capacity in terms of mass of CaCO3 rather than millequivalents.e. The practical exchange capacity is therefore rather less than the theoretical.1 and 1. Data Sheet I Backwash Figure 2 18 . A distinction must therefore be made between the dry and wet volumes and densities of a resin. Exchange Capacity The exchange capacity of a resin is a measure of the quantity of ions which can be exchanged per unit mass of volume of the resin. before placing in a test column. the attraction of water molecules to the ions) and the repulsion between the fixed ions. Laboratory Teaching Exercises Regenerate Figure 3 Softening Figure 4 19 . Armfield Instruction Manual Data Sheet II Backwash Figure 5 Figure 6 20 . Laboratory Teaching Exercises Regenerate Figure 7 Figure 8 21 . Armfield Instruction Manual Demineralise Figure 9 22 . typically 250ml Stoppered flask. typically 250ml capacity Wanklyn soap solution. typically 1 litre Procedure: Install the burette in its stand and fill the burette with Wanklyn soap solution.Laboratory Teaching Exercises Data Sheet III Schematic Diagram of UOP7 showing valve positions Data Sheet IV To determine the hardness of a sample of water using Wanklyn soap solution Equipment required (not supplied by Armfield Ltd): Burette. typically 100ml capacity Stand for burette Measuring cylinder. 23 . Observe if a lather forms on the surface of the sample. Hardness of water = mg of caCO3 of water Volume of water sample (ml) For example. Either adjust the sample of water to a known volume eg. Titrate 1ml of soap solution into the stoppered flask. Note the amount of soap solution added to the sample of water. Calculation of Hardness: Using Wanklyn soap solution. If no lather forms. Transfer the sample of water from the measuring cylinder to the stoppered flask. then the hardness of the water is: = 200mg of caCO3 per litre of water 24 . Repeat the addition of soap solution until a lather forms. if 10ml of soap solution is titrated into a 100ml sample of water before a lather forms. titrate another 1ml of soap solution into the sample and shake the contents. Insert the stopper and shake the contents.Armfield Instruction Manual Measure the volume of the sample of water using the measuring cylinder. 50 or 100ml or note the actual volume of the sample. 1ml of soap solution = 1mg of CaCO3. Do not drain the bed as this would allow air to enter. after allowing for the hardness already in the tap water. Figure 2 (Upward flow of water through the bed). Determine the hardness of this solution using Wanklyn soap solution (described in Data Sheet IV) or other method. (This is much harder than waters normally encountered. open valves V3 and V6. Determine hardness of each sample. but is used here in order to keep the duration of the softening experiment within reasonable limits). and backwash for five minutes at a flow sufficient to expand the bed by not more than 50% (typically 100 ml/min). Figure 3 (Downward flow of salt solution through the bed).Exercise A Objective To determine the exchange capacity of a cationic resin in the softening of water. Figure 4 (Downward flow of hard water through the bed). Before the salt solution is fully used up. open valves V2 and V10. 25 . Backwashing removes any sediment from the bed. Select tank D. Place this solution in regenerant tank B. and place it in the test water reservoir. continue the flow through the bed until the effluent no longer tastes salty. Softening See Data Sheet I. Backwashing See Data Sheet I. Fill tank D with distilled or deionised water (clean tap water can be used if more convenient). Set flowmeter to not more that 50ml/min. Select tank C. add distilled water to the regenerant tank. Continue the softening until the hardness of the effluent rises above 100mg/l as CaCO3. open valves V2. V12 (and V10 if a sample is required). Procedure Make up 10 litres of water with a hardness of between 600 and 700 mg/l as CaCO3 by dissolving an appropriate amount of calcium chloride in tap water. Fill the left hand cation exchanger column with cation resin (golden coloured granules) to a depth of 300mm. Collect samples of 500ml at five minute intervals. Make up 500ml of 10% w/v NaCl solution by dissolving 50g NaCl in distilled water. ensures that the resin beads are fully wetted and swollen and removes any air pockets which would interfere with the ion-exchange process. Select tank B. Gradually turn off the flow and measure the final depth of the resin. Regenerate See Data Sheet I. Set flowmeter to between 50 and 70ml/min. 26 . this is given by the area between the curve plotted and the horizontal line. Calculate the milligrams of hardness as CaCO3 removed from the water up to the breakthrough point. Knowing the wet volume of the resin bed. calculate the exchange capacity of the resin as meq/ml of wet volume. representing the original hardness of the water. Graphically.Armfield Instruction Manual Results and Calculations Plot the hardness readings against the volume of water treated and note the breakthrough point at which the increase in hardness starts. in order to determine practical regeneration efficiencies. These regeneration experiments must. calculate the efficiency of regeneration as a percentage. determine the meq of NaCl actually used in regeneration. Procedure After completion of the experiment 'SOFTENING'. Figure 2) to expel air before carrying out any further experiments. in operation it is not possible to apply this quantity precisely. Results and Calculations Final resin depth (mm) = Sodium ion concentration (meq) = Original quantity of NaCl Amount of NaCl collected = 342 meq (20g). ie. However. The efficiency will then be calculated by comparing the quantity of NaCl applied with the equivalent amount of hardness removed in experiment 'SOFTENING'. Knowing the volume of solution collected calculate the meq of NaCl which has passed through the bed. V10). draining the bed in doing so.) Determine the sodium ion concentration in the collected regenerant by measuring Na+ (after dilution) by flame photometry or other means. Further experiments may therefore be carried out using different quantities of NaCl for regeneration in solution from 5 to 10% in strength. the used regenerant solution should not be collected. carry out regeneration with 500ml of 10% w/v salt solution but this time collect the whole of this solution after it has passed through the bed (via valve no. The efficiency so calculated is based on the NaCl actually used in regeneration. = 27 . Hence by subtraction from the original quantity of NaCl applied (20g or 342 meq). (Note that having drained the bed in this experiment it will be necessary to backwash it (Data Sheet I. be alternated with softening experiments so that softening capacity can be correlated with regeneration efficiency. and an excess has to be applied.Exercise B Objective To determine the regeneration efficiency of an ion-exchange softening system. ie. when the hardness exchange capacity of the resin has been used up to just beyond the breakthrough point. and the distilled water should be used to flush out the last of the regenerant from the bed. of course. Compare this with the theoretical quantity of NaCl equivalent to the amount of hardness removed in the experiment 'SOFTENING' and hence. In these experiments the procedure should be as in the first experiment 'SOFTENING'. volume collected 28 .Armfield Instruction Manual Actual exchange capacity = original quantity . Regenerate the anion exchanger. calculate the total strength in meq/litre. Fill tank A with 500ml of a 10% hydrochloric acid solution. followed by distilled or demineralised water from tank D until pH of the effluent has returned to below 9. 29 . to flush out any surplus acid. In each case. the concentrations of the principal cations and anions. Measure the final depths of the two beds. as well as the total dissolved solids. Regenerate the cation exchanger. Procedure Fill the left hand cation column to a depth of 300mm with a cation exchanger resin (golden coloured granules) in the hydrogen ion form. Additional equipment required (Not supplied by Armfield): pH Meter Stop Clock Backwashing See Data Sheet II. must be determined if not already known (eg. Select tank A. This will be used in calculating the exchange capacities of the two resins. Follow the acid with distilled or demineralised water from tank D. Fill tank D with distilled or demineralised water. Figures 5 and 6 (Upward flow of water through the bed). Check pH of effluent and continue flushing until pH has returned to above 5. open valves V1 and V15.0. Fill tank B with 500ml of a 5% sodium hydroxide solution. from the water undertaking's figures). Regeneration (ANION) See Data Sheet II. Demineralisation See Data Sheet II.Exercise C Objective To study the demineralisation of water and to determine the exchange capacities of a hydrogen ion cation exchanger and an anion exchanger. If tap water is used. open valves V2 and V12. Figure 7 (Downward flow of acid through the cation bed). The electrical conductivity should also be measured. Each column should be separately backwashed in the manner described in experiment 'SOFTENING'. Regeneration (CATION) See Data Sheet II. From a knowledge of the concentrations of the main cations and anions in the water to be used. Fill tank C with 10 litres of test water containing 800 to 1000mg/l of dissolved solids. Fill the anion column to a depth of 300mm with an anion exchange resin (white coloured granules) in the hydroxyl form. Figure 8 (Downward flow of sodium hydroxide through the anion bed). the rate of backwashing should be controlled to give not more than 50% expansion of the bed. Select tank B. Figure 9 (Downward flow of test water through both columns in series).0. V16 and measure its pH. it indicates that the cation exchanger has become exhausted.e. To convert conductivity values to meq/l For water with a given content of salts. take another small sample from valve no. it is sufficiently 30 . Set flow rate to between 50 and 70ml/min. it is necessary to convert pH or conductivity readings to meq/litre. and its capacity can be calculated. collecting the water which passes through it and measuring pH values until the breakthrough point.Armfield Instruction Manual Select tank C. If. a. the breakthrough point at which one of the resins has become exhausted. on the other hand. i. If this pH is higher than the values previously recorded. To convert pH values to meq/l If pH reading is x Hydrogen ion concentration = 10-x gram-moles/litre = 103-x meq/litre b. the rising conductivity of the final effluent indicates that the anion exchanger is exhausted. In order to calculate the exchange capacities in terms of millequivalents. and the exchange capacity of the cation exchanger calculated. Although these solids consist of several salts of varying electrolytic properties. Note the time when the conductivity of the demineralised water begins to rise. the electrical conductivity is closely proportional to the concentration of total dissolved solids. V13 and V15. The experiment should be stopped at this point. when the pH begins to rise. the exchange capacity of the cation exchanger can be determined by continuing the flow of water through the first column only. open valves V2. As soon as possible after this point. It is then possible to determine the exchange capacity of the anion exchanger in this experiment. It is advisable to confirm this by drawing one or two further samples for pH determination. the pH of the cation exchanger effluent continues at a low value. the breakthrough point is detected by readings of pH (for the cation exchanger) or conductivity (for the anion exchanger) instead of by direct measurement of concentrations as in the softening experiment. In the latter event. Note time at which flow is started and take conductivity readings at 5 minute intervals. At 20 minute intervals draw off samples from valve V10 and measure the pH value. Results and Calculations In the demineralisation experiment. Exercise C accurate to assume that electrical conductivity is also proportional to the total concentration in terms of meq/litre. 31 . In any event these figures should be very low. The constant of proportionality was established by determination of the electrical conductivity and the strength of meq/l of the raw water. Hence the electrical conductivity of the demineralised water can be converted to meq/l. Final Depths: CATION = ANION = Exchange capacities can now be calculated. Results and Calculations Final Depth (CATION) Final Depth (ANION) = = Sodium ion concentration (meq/ml) = Original quantity of sodium hydroxide used = Amount of sodium hydroxide collected = Actual exchange capacity = Original quantity . open valves V2 and V10. Regenerate Select tank A. Note: Since the exchange capacities of cation resins are generally greater than those of anion resins. Fill tank B with 500 ml of a 5% sodium hydroxide solution. Fill tank D with distilled or demineralised water. Procedure CATION RESIN Fill tank A with 500ml of a 10% hydrochloric acid. ANION RESIN To determine the regeneration efficiency of the anion resin it will be necessary to carry out the full demineralisation experiment 'DEMINERALISATION'. Collect the whole of the solution.Exercise D Objective To determine the regeneration efficiency of a cation resin and an anion resin. open valves V3 and V6. it is expected that the anion resin will be first to be exhausted. Fill tank C with 10 litres of test water. Backwash Select tank D.amount used 32 . Contact Details for Further Information Main Office: Armfield Limited Bridge House West Street Ringwood Hampshire England BH24 1DY Tel: +44 (0)1425 478781 Fax: +44 (0)1425 470916 Email: [email protected]. NJ 08510 Tel/Fax: (609) 208 2800 Email: [email protected] [email protected] US Office: Armfield Inc.co.Lakewood Road Clarksburg.uk Web: http://www.com 33 . 9 Trenton .