16593 09 tủ tài liệu bách khoa
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16593 09 tủ tài liệu bách khoa
______CHAPTER 9_____ION EXCHANGE AND INORGANIC ADSORPTIONDennis A. Clifford, Ph D., P.E., DEEProfessor and chairman Department of Civil and Environ me 16593 09 tủ tài liệu bách khoaental Engineering Un ivers ity of II o USỈO n Houston, TexasINTRODUCTION AND THEORY OF ION EXCHANGEContaminant cations such as calcium, magnesium, barium, strontium, and radium, and anions such as fluoride, nitrate, fulvatcs. humates. arsenate, selenate. chromate, and anionic complexes of uranium ca 16593 09 tủ tài liệu bách khoan be removed from waler by using ion exchange with resins or by adsorption onto hydrous metal oxides such as activated alumina (A Al) granules or coag16593 09 tủ tài liệu bách khoa
ulated Fe(ĩĩ). Fe(TTI), AI(TTI),and Mn(IV) surfaces. This chapter deals only with the theory and practice of ion exchange with resins and adsorption w______CHAPTER 9_____ION EXCHANGE AND INORGANIC ADSORPTIONDennis A. Clifford, Ph D., P.E., DEEProfessor and chairman Department of Civil and Environ me 16593 09 tủ tài liệu bách khoatumm's publications on the solid-water interface (Schindler. 1981: Stumm. 1992) as a starting point.Ion exchange with synthetic resins and adsorption onto activated alumina arc water treatment processes in which a presaturant ion on the solid phase, the adsorbent, is exchanged for an unwanted ion in 16593 09 tủ tài liệu bách khoa the water. In order to accomplish the exchange reaction, a packed bed of ion-exchange resin beads or alumina granules is used. Source water is contin16593 09 tủ tài liệu bách khoa
ually passed through the bed in a downflow or upflow mode until the adsorbent is exhausted, as evidenced by the appearance (breakthrough) of the unwan______CHAPTER 9_____ION EXCHANGE AND INORGANIC ADSORPTIONDennis A. Clifford, Ph D., P.E., DEEProfessor and chairman Department of Civil and Environ me 16593 09 tủ tài liệu bách khoaausted bed is regenerated using an excess of the presaturant ion. Ideally, no per-manpnt ctrnrtiiral rhz'inop mlfPA nlíipp ilnrino thp pvhnn-srinn/rpopiipmrinn rvelp9.2CHAPTER NINEregeneration.) When the reactions are reversible, the medium can be reused many times before it must be replaced because 16593 09 tủ tài liệu bách khoa of irreversible fouling or. in the case of alumina. excessive attrition. In a typical water supply application, from 300 to as many as 300.000 bed vo16593 09 tủ tài liệu bách khoa
lumes (BV) of contaminated water may be treated before exhaustion. Regeneration typically requires from 1 to 5 bed volumes of regenerant, followed by ______CHAPTER 9_____ION EXCHANGE AND INORGANIC ADSORPTIONDennis A. Clifford, Ph D., P.E., DEEProfessor and chairman Department of Civil and Environ me 16593 09 tủ tài liệu bách khoaal is a major consideration in modern design practice. Disposal of the spent media may also present a problem if it contains a toxic or radioactive substance such as arsenic or radium.Uses of Ion Exchange in Water TreatmentBy far the largest application of ion exchange to drinking water treatment is 16593 09 tủ tài liệu bách khoa in the area of softening, that is. the removal of calcium, magnesium, and other polyvalent cations in exchange for sodium. The ion-exchange softening16593 09 tủ tài liệu bách khoa
process is applicable to both individual home use and municipal treatment. Il can be applied for wholehouse (poini-of-entry or POE) softening or for ______CHAPTER 9_____ION EXCHANGE AND INORGANIC ADSORPTIONDennis A. Clifford, Ph D., P.E., DEEProfessor and chairman Department of Civil and Environ me 16593 09 tủ tài liệu bách khoa former are also effectively removed during ionexchange softening. Resins beds containing chloride-form anion exchange resins can be used for nitrate, arsenate, chromate, selenale, dissolved organic carbon (DOC), and uranium removal, and more applications of these processes will be seen in the futur 16593 09 tủ tài liệu bách khoae. Activated alumina is being used to remove fluoride and arsenate from drinking waler, particularly high Total dissolved solids (TDS) walers, al poin16593 09 tủ tài liệu bách khoa
l-of-use (POU). (POE), and municipal scales.The choice between ion exchange or alumina adsorption (to remove arsenic from water, for example) is large______CHAPTER 9_____ION EXCHANGE AND INORGANIC ADSORPTIONDennis A. Clifford, Ph D., P.E., DEEProfessor and chairman Department of Civil and Environ me 16593 09 tủ tài liệu bách khoar alumina affinity for the contaminant ion in comparison with the competing ions. The affinity sequence determines the run length, chromatographic peaking (if any), and process costs. As previously mentioned, process selection will be affected by spent regenerant and spent medium disposal requiremen 16593 09 tủ tài liệu bách khoats, and regenerant reuse possibilities, particularly if hazardous materials are involved. Each of these requirements is dealt with in some detail in t16593 09 tủ tài liệu bách khoa
he upcoming design sections for the specific processes summarized in Table 9.1.Past and Future of Ion ExchangeNatural zeolites (i.e..crystalline alumi______CHAPTER 9_____ION EXCHANGE AND INORGANIC ADSORPTIONDennis A. Clifford, Ph D., P.E., DEEProfessor and chairman Department of Civil and Environ me 16593 09 tủ tài liệu bách khoacause of the lattcrs' faster exchange rates, longer life, and higher capacity. Aside from softening, the use of ion exchange for removal of specific contaminants from municipal water supplies has been limited. Illis is primarily because of the expense involved in removing what is perceived as only a 16593 09 tủ tài liệu bách khoa minimal health risk resulting from contaminants such as fluoride, nitrate, or chromate. Hie production of pure and ultrapure water by ion-exchange de16593 09 tủ tài liệu bách khoa
mineralization (IXDM) is the largest use of ion exchange resins on a commercial scale. The complete removal of contam-inonfc iiihÌAli A/'i'lirc ininof______CHAPTER 9_____ION EXCHANGE AND INORGANIC ADSORPTIONDennis A. Clifford, Ph D., P.E., DEEProfessor and chairman Department of Civil and Environ me 16593 09 tủ tài liệu bách khoaed Inorganic Contaminant Removal ProcessesIon exchangeAdvantages•Operates on demand.•Relatively insensitive to flow variations, short contact time required.•Relatively insensitive to trace-level contaminant concentration.•Essentially zero level of effluent contaminant possible.•Large variety of spec 16593 09 tủ tài liệu bách khoaific resins available.•Beneficial selectivity reversal commonly occurs upon regeneration.•In some applications, spent regenerant may be reused without16593 09 tủ tài liệu bách khoa
contaminant removal.Disadvantages•Potential for chromatographic effluent peaking when using single beds.•Variable effluent quality with respect to ba______CHAPTER 9_____ION EXCHANGE AND INORGANIC ADSORPTIONDennis A. Clifford, Ph D., P.E., DEEProfessor and chairman Department of Civil and Environ me 16593 09 tủ tài liệu bách khoae used and disposed of.Activated alumina adsorptionAdvantages•Operates on demand.•Relatively insensitive to total dissolved solids and sulfate levels.______CHAPTER 9_____ION EXCHANGE AND INORGANIC ADSORPTIONDennis A. Clifford, Ph D., P.E., DEEProfessor and chairman Department of Civil and Environ meGọi ngay
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