电絮凝ApplicationofElectrocoagulationProcessinR

Int.J.Environ.Res.,4(2):201-208,Spring2010ISSN:1735-6865201Received23July2009;Revised12Jan.2010;Accepted5Feb.2010*CorrespondingauthorE-mail:[e-mail]oagulationProcessinRemovalofZincandCopperFromAqueousSolutionsbyAluminumElectrodesNouri,J.1,Mahvi,A.H.2,3andBazrafshan,E.4*1DepartmentofEnvironmentalManagement,GraduateSchooloftheEnvironmentandEnergy,ScienceandResearchBranch,IslamicAzadUniversity,Tehran,Iran2SchoolofPublicHealthandCenterforEnvironmentalResearch,TehranUniversityofMedicalSciences,Tehran,Iran3NationalInstituteofHealthResearch,MinistryofHealth,Tehran,Iran4SchoolofPublicHealth,ZahedanUniversityofMedicalSciences,Zahedan,IranABSTRACT:Inthisstudy,theperformanceofelectro-coagulationincombinationwithaluminumsacrificialanode,inremovalofzincandcopperhasbeeninvestigated.Severalparameters,suchaspollutantconcentration,pH,electricalpotential,COD,turbidityandcontacttimewerestudiedtoachieveahigherremovalcapacity.Variableconcentrations(5-50-500ppm)ofzincandcoppersolu-tionswereprepared.Inordertofollowtheprogressofthetreatment,samplesof25mLweretakenat15minintervalsupto60minandthenfilteredwith0.45ىdiametertoeliminatesludgeformedduringelectrolysis.ThevaryingpHoftheinitialsolutionwasalsostudiedtomeasuretheireffectsonthezincandcopperremovalefficiency.Resultsobtainedwithsyntheticwastewaterrevealedthatthemosteffectiveremovalcapacitiesofstudiedmetalscouldbeachievedat40Velectricalpotential.Inaddition,theincreaseofelectricalpotential,intherangeof20-40V,enhancedthetreatmentratewithoutaffectingthechargeloadingrequiredtoreducemetalionconcentrationsundertheadmis-siblelegallevels.Theprocesswassuccessfullyappliedtothetreatmentofanelectroplatingwaste-waterwhereaneffectivereductionofzincandcopperconcentrationunderlegallimitswasobtained,justafter15-60min.Moreover,itcanbeconcludedthattheelectro-coagulationprocesshasthepotentialtobeutilizedforthecost-effectiveremovalofheavymetalsfromwaterandwastewater.Keywords:Electro-coagulation,Zincandcopperremoval,AluminumelectrodesINTRODUCTIONInrecentyears,therehasbeenanincreasingpub-licawarenessofthelong-termeffectofwatercontainingdissolvedheavymetalions(Sonetal,2004).Heavymetals,suchaschromium,cadmium,copper,zincandnickel,arecontainedinindustrialwastewater,whichpollutestheenvironmentandstronglyaffectshumanhealth;Inthisregard,thepreventionofenvironmentalpollutionhasactivelybeenstudied(ChoiandKim,2003;Nourietal.,2006;Mahvi,2008);Samarghandi,etal.,2007;Nourietal.,2008).Toxicheavymetalsarere-leasedintotheenvironmentfromanumberofin-dustriessuchasmining,plating,dyeing,automo-bilemanufacturingandmetalprocessing.Thepresenceofheavymetalsintheenvironmenthasledtoanumberofenvironmentalproblems(VinodhiniandNarayanan,2008).Inordertomeetthewaterqualitystandardsformostcountries,theconcentrationofheavymetalsinwastewatermustbecontrolled(Kimetal,2005;Mahvietal.,2007;Rahmanietal.,2009;Asgari,2008).Sepa-rationtechniquesofheavymetals,suchaschro-mium,cadmium,copper,zincandnickel,fromin-dustrialwastewaterincludeprecipitation,ionex-change,adsorption,electro-dialysisandfiltration(Abdel-Ghanietal.,2009;Malakootianetal.,2009),butthesetechniqueshavelimitationsinArchiveofSID(ChoiandKim,2005).Duringthepastyears,Electro-co-agulationmethodhasbeenproposedasaneffec-tivemethodtotreatvariouswastewaterssuchaslandfillleachate,restaurantwastewater,salinewastewater,tarsandandoilshalewastewater,urbanwastewater,laundrywastewater,nitrateandarsenicbearingwastewaterandchemicalme-chanicalpolishingwastewater(Niametal.,2007;Schulzetal.,2009;Karbassi,etal.,2008a).Electro-coagulationisasimpleandefficientmethodtoremovetheflocculatingagentgener-atedbyelectro-oxidationofasacrificialanodeanodeandgenerallymadeofironoraluminum.Inthisprocess,thetreatmentisperformedwithoutaddinganychemicalcoagulantorflocculants.Thus,reducingtheamountofsludgewhichmustbedisposed(CenkinandBelevstev,1985).Ontheotherhand,electrocoagulationisbasedontheinsituformationofthecoagulantasthesacrificialanodecorrodesduetoanappliedcurrent,whilethesimultaneousevolutionofhydrogenatthecath-odeallowsforpollutantremovalbyflotation.Thistechniquecombinesthreemaininterdependentprocesses,operatingsynergisticallytoremovepollutants:electrochemistry,coagulationandhy-drodynamics.Anexaminationofthechemicalre-actionsoccurringintheelectrocoagulationpro-cessshowsthatthemainreactionsoccurringattheelectrodes(aluminumelectrodes)are:Al↔Al3++3e(anode)(1)3H2O+3e↔3/2H2+3OH-(cathode)(2)Inaddition,Al3+andOH”ionsgeneratedatelec-trodesurfacesreactinthebulkwastewatertoformaluminumhydroxide:Al3++3OH-↔Al(OH)3(3)Iftheanodepotentialissufficientlyhigh,second-aryreactionsmayoccurattheanode,suchasdirectoxidationoforganiccompoundsandofH2OorCl”presentinwastewater:2Cl-↔Cl2+2e(4)2H2O↔O2+4H++4e(5)Theproducedchlorineundergoesadis-mutationreactionatpHhigherthan3–4:Cl2+H2O↔HClO+H++Cl-(6)HClO↔ClO-+H+(7)Thealuminumhydroxideflocsnormallyactasadsorbentsand/ortrapsformetalions.There-fore,theywouldelimin