16593 10 tủ tài liệu bách khoa
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16593 10 tủ tài liệu bách khoa
_______CHAPTER 10_____CHEMICAL PRECIPITATIONLarry D. Benefield, Ph D.Professor Department of Civil Engineering Auburn University, AlabamaJoe M. Morgan 16593 10 tủ tài liệu bách khoan, Ph.D.Associate Professor Department of Civil Engineering Auburn University. AlabamaChemical precipitation is an effective treatment process for the removal of many contaminants. Coagulation with alum, ferric sulfate, or ferrous sulfate and lime softening both involve chemical precipitation. The r 16593 10 tủ tài liệu bách khoaemovability of substances from water by precipitation depends primarily on the solubility of the various complexes formed in water For example, heavy16593 10 tủ tài liệu bách khoa
metals are found as cations in water and many will form both hydroxide and carbonate solid forms. These solids have low solubility limits in water. Th_______CHAPTER 10_____CHEMICAL PRECIPITATIONLarry D. Benefield, Ph D.Professor Department of Civil Engineering Auburn University, AlabamaJoe M. Morgan 16593 10 tủ tài liệu bách khoaum, ferric sulfate, or ferrous sulfate involves chemical precipitation, extensive coverage of coagulation is given in Chapter 6 and will not be repeated here. The discussion of the application of chemical precipitation in water treatment presented in this chapter will emphasize the reduction in the 16593 10 tủ tài liệu bách khoaconcentration of calcium and magnesium (water softening) and the reduction in the concentration of iron and manganese Attention will also be given to16593 10 tủ tài liệu bách khoa
the removal of heavy metals, radionuclides, and organic materials in the latter part of the chapterFUNDAMENTALS OF CHEMICAL PRECIPITATIONChemical prec_______CHAPTER 10_____CHEMICAL PRECIPITATIONLarry D. Benefield, Ph D.Professor Department of Civil Engineering Auburn University, AlabamaJoe M. Morgan 16593 10 tủ tài liệu bách khoaficiencies. Reasons for such variability will be explored in this chapter by considering precipitation theory and translating this into problems encountered in actual10.10CHAPTER TENI'lGl Kh 1UJ Concentration distribution diagram for carbonic and. (Scwrrr/ ỉỉo/ỉtibơok o f Water Resources and Polluti 16593 10 tủ tài liệu bách khoaon Control H. w. Gthrti and J. I. Bregman. e16593 10 tủ tài liệu bách khoa
in the soluble calcium concentration.lhe solubility equilibrium for Mg(OH): IS described byMg(OH)2(.c) - Mg2* + 20 H*(10.28)According to LeChateliers_______CHAPTER 10_____CHEMICAL PRECIPITATIONLarry D. Benefield, Ph D.Professor Department of Civil Engineering Auburn University, AlabamaJoe M. Morgan 16593 10 tủ tài liệu bách khoatation of Mg(OH)i and a corresponding decrease in the soluble magnesium concentration.The solubility product expressions for Equations 10.27 and 10.28 have the forms ^=[Ca-1(COr](10.29)KT=[Mg-‘|[OH ](10.30)The effects of temperature on the solubility product constants for calcium carbonate and magne 16593 10 tủ tài liệu bách khoasium hydroxide is given by the empirical equations (Rossum and Merrill. 1983; Faust and McWhorter. 1976; Lowcnthal and Marais. 1976)Calcium carbonate:16593 10 tủ tài liệu bách khoa
Kip = Ị(yrofl0-tt5wr-4MMsn(10.31)Magnesium hydroxide: K.p =-10,32where T and f are the solution temperature in tìK and dC, respectively. The Kw for c_______CHAPTER 10_____CHEMICAL PRECIPITATIONLarry D. Benefield, Ph D.Professor Department of Civil Engineering Auburn University, AlabamaJoe M. Morgan 16593 10 tủ tài liệu bách khoalummer ..„,4A DU A A\1HUA/momTABLE 10.2 Complex Ion Formation Reactions of CakiUin and Magnesium Ions*ReactionEquilibrium constantTemperature corrcctior1 7. K1.Calcium a Ca’* + OH * CaOH* b.Ca^ + HCO, *Calico? c.Cr” + cox'- - CaCO? c d.Ca'■ + so?" — CaSOi" 2.-Magnesium a. Mg'-+ OH"—MgOH*A’. = (CaOHp 16593 10 tủ tài liệu bách khoaKa -||OH 1 A, = (Calico |/(Ca- JiHCO, K. = (CaCO(’J|Ca-‘](CO,? 1 A\= (CaSOrj/fCa •((SO/-) K - = [MgOH*J(Mg:’](OH"JpKj =-1.299 - 26OJS8 1/T- 1/298.15 J16593 10 tủ tài liệu bách khoa
^4 = 2.95-0.01337 pK? = 27.393 - 4114/7 - 0.056177 pK* = 691.70/7 pKT = -0.6S4 - 0.00517b.Mg3- + HCOj- - MgHCO.-.* c.Mr +CO.’ -.MgCO? d Mì'- + SOr - M_______CHAPTER 10_____CHEMICAL PRECIPITATIONLarry D. Benefield, Ph D.Professor Department of Civil Engineering Auburn University, AlabamaJoe M. Morgan 16593 10 tủ tài liệu bách khoa 707.07/7• TcmpcNturc concclions arc from Truesdell and Jones (I973).10.12CHAPTER TENdetermine the eifect of complex ion formation on calcium carbonate and magnesium hydroxide solubility by writing mass balance relationships for total residual calcium and total residual magnesium that consider these 16593 10 tủ tài liệu bách khoa species. Such relationships have the form|( ’a]i = [Ca2*] + [CaOtT] + [CaHCO;] + |( a( oy] + [CaSOi](10.33)that reduces to4Z / K\|Ca)r= —yr 11 ++ K|U16593 10 tủ tài liệu bách khoa
|Cjr4- KĩUĩCt + Kjsoj'l I_______CHAPTER 10_____CHEMICAL PRECIPITATIONLarry D. Benefield, Ph D.Professor Department of Civil Engineering Auburn University, AlabamaJoe M. Morgan_______CHAPTER 10_____CHEMICAL PRECIPITATIONLarry D. Benefield, Ph D.Professor Department of Civil Engineering Auburn University, AlabamaJoe M. MorganGọi ngay
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