电絮凝ArsenicRemovalfromUndergroundWaterbyElec

209thECSMeeting,Abstract#884,copyrightECSArsenicRemovalfromUndergroundWaterbyElectrocoagulationwithZinc,BrassandIronC.Montero-Ocampo*andA.MaldonadoCINVESTAV-IPN,U.Saltillo,Aptdo.Postal663,25900Saltillo,Coah.,MéxicoArseniccontaminationofgroundwateroccursbybothnaturalprocessessuchasweatheringofarseniccontainingmineralsanduncontrolledindustrialdischargefromminingandmetallurgicalindustries,pesticides,andfertilizerproduction.Arsenate(As(V))isoneoftheprimaryformsofarsenicinsoilsandnaturalwaters(1).Duetothehightoxiceffectsofarseniconhumanhealth(itsingestionmaydeleteriouslyaffectthegastrointestinaltract,cardiac,vascularsystemandcentralnervoussystem(2)),itsmaximumlevelindrinkingwateris10µg/L.Therefore,arsenicremovalfromcontaminatedundergroundwaterfordrinkingpurposeswithlevels~130µg/Lisnecessarytoreduceitsconcentrationtothementionedmaximumadmissible.Commonmethodstoremovearsenicfromwaterareadsorptiontechniques,whichincludeprecipitationwithironandaluminiumsalts(3),adsorptionontoactivatedalumina,activatedcarbonandactivatedbauxite(4).Amongthesemethods,theelectrochemicalmethodofelectrocoagulation(EC)isanemergingwatertreatmentthathasbeenappliedsuccessfullytotreatpotablewater,urbanwastewater,andheavymetalwastewater(5).TheECmethodhastheadvantageofproducingnosludge.Thismethodofferspossibilityofinsitugenerationofadsorbentsbyanodicdissolutionofappropriatesacrificialanodes.TheobjectiveofthepresentstudywastoevaluatetheefficacyofAs(V)removalfromamodelundergroundwater(concentrationvaryingfrom70to130µg/L)bydifferentelectrodematerialssuchaszinc,ironandbrass.TheAs(V)removalwascarriedoutatconstantcurrentconditions,1.5mA/cm2for60min.Theworkingelectrodeswerediscsofiron,zinc,brassandcopperwitha1cm2areaand3mmthickness.BeforetheAs(V)removaltreatment,thediscswerepolishedwithvariousgradesofSiCgrindingpaper(upto2400grit)and0.05µmaluminaslurry,rinsedwithwaterandwashedwithacetone.Amodelundergroundwater(0.750L)containinganAs(V)concentrationfrom70to130µg/Lwaspreparedfromasodiumarsenate(Na2HAsO4.7H2O)stocksolution.FullremovalofAs(V)hasalmostbeenachievedascanbeseenwithiron(Figure1(a))andzinc(Figure1(b)).Thereactionsattheanodeandcathodeareasfollows:Atcathodethewaterreductionisproduced:2H2O+2eÆH2+2OH-Atanode:theactivationprocessofzinc,brassandironisobtained.Thereactionsattheironanodemightbewrittenasfollows:FeÆFe2++2eFe2++2OH-ÆFe(OH)22Fe2++½O2+4OH-Æ2FeOOH+H2OFe(a)Time(min)010203040506070As(V)concentration(ppm)0,000,020,040,060,080,100,120,140.128ppm0.076ppm0.130ppmZnb)Time(min)010203040506070As(V)concentración(ppm)0,000,020,040,060,080,100,120,140.070ppm0.130ppm0.110ppmFigure1.As(V)removalwith(a)iron,and(b)zincelectrodes.REFERENCES1.J.F.Ferguson,J.Gavis,WaterRes.6(1972)1259-1274.2.W.J.Farrell,O.D.Peggy,M.Colklin,Environ.Sci.Technol.,35(2001)2026-2032.3.J.G.Hering,P.Y.Chen,J.A.Wilkie,M.Elimelech.,J.AmWaterWorksAssoc.88(1996)155-167.4.S.K.Gupta,K.Y.Chen,J.WaterPollut.ControlFed.50(1978)493-506.5.P.K.Holt,G.W.Barton,M.Wark,Collo.Surf.:APhys.Chem.Eng.Aspe.211(2002)233-248.