搜索
Iran.J.Environ.Health.Sci.Eng.,2006,Vol.3,No.4,pp.261-266*Correspondingauthor-Email:ahmahvi@yahoo.comTel:+982188954914,Fax:+982188950188261REMOVALOFCADMIUMFROMINDUSTRIALEFFLUENTSBYELECTROCOAGULATIONPROCESSUSINGIRONELECTRODESE.Bazrafshan,∗A.H.Mahvi,S.Nasseri,A.R.Mesdaghinia,F.Vaezi,Sh.NazmaraDepartmentofEnvironmentalHealthEngineering,SchoolofPublicHealthandCenterforEnvironmentalResearch,MedicalSciences/UniversityofTehran,Tehran,IranReceived10August2006;revised30August2006;accepted25September2006ABSTRACTTheobjectofthisstudyistheevaluationofcadmiumremovalfromindustrialwastewaterbyelectrocoagulationprocess.Forthisstudyaglasstankin1.56Lvolumewithfourplateelectrodewasusedtodoexperiments.TheelectrodesmadeofironandconnecttothepositiveandnegativepoleofDCpowersupply(bipolarmode).Thetankwasfilledwithsyntheticwastewaterthatwascontainingcadmiumioninconcentration5,50and500mg/Landthenitwasstartedup.ThepercentofcadmiumionremovalwasmeasuredatpH3,7and10andinelectricpotentialrangeof20,30and40volts.Attheendofeachstageofexperiment,volumeofproducedsludgewasmeasured.Theresultsobtainedatdifferentelectricalpotentialshowedthatinitialconcentrationofcadmiumcaneffectonefficiencyremovalandforhigherconcentrationofcadmium,higherelectricalpotentialormorereactiontimeisneeded.Ontheotherhand,iftheinitialconcentrationincreases,thetimerequiredofprocessshouldincreasetoo.ThefinalpHforironelectrodeswasalwayshigherthaninitialpH.Asexpected,theresultsshowedthatforagiventime,theremovalefficiencyincreasedsignificantlywithincreaseofcurrentdensity.Thehighestelectricalpotential(40V)producedthequickesttreatmentwith99%cadmiumreductionoccurringafteronly20min.Theresultshowedthat,inthisprocess,theuseofdifferentelectricalpotentialscanprovideawiderangeofpHfordoingthisprocessandelectrocoagulationprocess(usingironelectrodes)isareliable,safety,efficientandcost-effectivemethodforremovalofcadmiumfromindustrialeffluents,especiallydesignedforpH=10andvoltage=40V.Keywords:Electrocoagulationprocess,cadmiumremoval,Ironelectrodes,industrialeffluentsINTRODUCTIONHeavymetalspeciesaresomeofthemostcommonpollutantsthatarefoundinindustrialwastewaters.Becauseoftheirtoxicity,thesespeciescanhaveaseriousimpactifreleasedintotheenvironmentasaresultofbioaccumulation,andtheymaybeextremelytoxicevenintracequantities.Onesuchaheavymetal,cadmium,alongwithitscompounds,iswidelyusedinpigments,asheatstabilizersforplastics,forcorrosionresistanceofsteelandcastiron,metalplating,phosphatefertilizer,mining,pigments,alloyindustries,insolderingandbrazing,andinthebatteryindustry(Ni-Cdbatteries).Cadmiumishighlytoxicandthereissomeevidencethatitiscarcinogenic(HiattandHuff,1975).TheharmfuleffectsofCadmiumincludeanumberofacuteandchronicdisorders,suchas“itai-itai”disease,renaldamage,emphysema,hypertension,andtesticularatrophy(WHO,1984;Leyva-Ramos,1997).Wheningestedbyhumanbeings,cadmiumthatisnotexcretedimmediatelyhasalonghalf-lifeofseveralhundreddays,sothatalowdoseexposureoveralongperiodoftimecanleadtoahighbodyburden.Inviewofitspersistenceasacumulativepoisonandthelowtoleranceofthehumanbodytowardscadmium,itisofinteresttodevelopschemesfortheremovalofheavymetalsfromwastewaterspriortotheirdisposal.Suchdisposalis,ofcourse,subjecttostrictenvironmentalregulation.Inthecaseofcadmium,forexample,theimmobilizationandremobilizationofCd(II)byferrihydrite,andtheeffectofCd(II)onthe !#$%&'%()&*$+$(#%$ ! # $ % & '(%&'! ) *+ %&' )!, ( * -! , . /01 $ $ 2# ! ' 3 . $ & *'! 4'&! ( . &$ $ $ $ $ 5 -0 2# ! ,$ $ $ $ $ 6 7 $ 7 8*! 9: $ $ ; # 8* 2 5 0!, .!9 9: : = !* !&' :