Removal-of-heavy-metal-ions-from-wastewaters-A-rev

ReviewRemovalofheavymetalionsfromwastewaters:AreviewFenglianFua,*,QiWangbaFacultyofEnvironmentalScienceandEngineering,GuangdongUniversityofTechnology,Guangzhou510006,PRChinabFacultyofAppliedMathematics,GuangdongUniversityofTechnology,Guangzhou510006,PRChinaarticleinfoArticlehistory:Received4March2010Receivedinrevisedform16October2010Accepted9November2010Availableonline8December2010Keywords:HeavymetalwastewaterTreatmenttechnologyReviewabstractHeavymetalpollutionhasbecomeoneofthemostseriousenvironmentalproblemstoday.Thetreat-mentofheavymetalsisofspecialconcernduetotheirrecalcitranceandpersistenceintheenvironment.Inrecentyears,variousmethodsforheavymetalremovalfromwastewaterhavebeenextensivelystudied.Thispaperreviewsthecurrentmethodsthathavebeenusedtotreatheavymetalwastewaterandevaluatesthesetechniques.Thesetechnologiesincludechemicalprecipitation,ion-exchange,adsorption,membranefiltration,coagulationeflocculation,flotationandelectrochemicalmethods.About185publishedstudies(1988e2010)arereviewedinthispaper.Itisevidentfromtheliteraturesurveyarticlesthation-exchange,adsorptionandmembranefiltrationarethemostfrequentlystudiedforthetreatmentofheavymetalwastewater.
2010ElsevierLtd.Allrightsreserved.1.IntroductionHeavymetalsareelementshavingatomicweightsbetween63.5and200.6,andaspecificgravitygreaterthan5.0(SrivastavaandMajumder,2008).Withtherapiddevelopmentofindustriessuchasmetalplatingfacilities,miningoperations,fertilizerindustries,tanneries,batteries,paperindustriesandpesticides,etc.,heavymetalswastewatersaredirectlyorindirectlydischargedintotheenvironmentincreasingly,especiallyindevelopingcountries.Unlikeorganiccontaminants,heavymetalsarenotbiodegradableandtendtoaccumulateinlivingorganismsandmanyheavymetalionsareknowntobetoxicorcarcinogenic.Toxicheavymetalsofparticularconcernintreatmentofindustrialwastewatersincludezinc,copper,nickel,mercury,cadmium,leadandchromium.Zincisatraceelementthatisessentialforhumanhealth.Itisimportantforthephysiologicalfunctionsoflivingtissueandregulatesmanybiochemicalprocesses.However,toomuchzinccancauseeminenthealthproblems,suchasstomachcramps,skinirritations,vomiting,nauseaandanemia(Oyaroetal.,2007).Copperdoesessentialworkinanimalmetabolism.Buttheexces-siveingestionofcopperbringsaboutserioustoxicologicalconcerns,suchasvomiting,cramps,convulsions,orevendeath(Paulinoetal.,2006).Nickelexceedingitscriticallevelmightbringaboutseriouslungandkidneyproblemsasidefromgastrointestinaldistress,pulmo-naryfibrosisandskindermatitis(Borbaetal.,2006).Anditisknownthatnickelishumancarcinogen.Mercuryisaneurotoxinthatcancausedamagetothecentralnervoussystem.Highconcentrationsofmercurycauseimpairmentofpulmonaryandkidneyfunction,chestpainanddyspnoea(NamasivayamandKadirvelu,1999).TheclassicexampleofmercurypoisoningisMinamataBay.CadmiumhasbeenclassifiedbyU.S.EnvironmentalProtectionAgencyasaprobablehumancarcinogen.Cadmiumexposeshumanhealthtosevererisks.Chronicexposureofcadmiumresultsinkidneydysfunctionandhighlevelsofexposurewillresultindeath.Leadcancausecentralnervoussystemdamage.Leadcanalsodamagethekidney,liverandreproductivesystem,basiccellularprocessesandbrainfunctions.Thetoxicsymptomsareanemia,insomnia,headache,dizziness,irritability,weaknessofmuscles,hallucinationandrenaldamages(NaseemandTahir,2001).Chro-miumexitsintheaquaticenvironmentmainlyintwostates:Cr(III)andCr(VI).Ingeneral,Cr(VI)ismoretoxicthanCr(III).Cr(VI)affectshumanphysiology,accumulatesinthefoodchainandcausesseverehealthproblemsrangingfromsimpleskinirritationtolungcarci-noma(KhezamiandCapart,2005).Facedwithmoreandmorestringentregulations,nowadaysheavymetalsaretheenvironmentalprioritypollutantsandarebecomingoneofthemostseriousenvironmentalproblems.Sothesetoxicheavymetalsshouldberemovedfromthewastewatertoprotectthepeopleandtheenvironment.Manymethodsthatarebeingusedtoremoveheavymetalionsincludechemicalprecipi-tation,ion-exchange,adsorption,membranefiltration,electro-chemicaltreatmenttechnologies,etc.Thepresentreviewarticledealswiththecurrenttechniquesfortheremovalofheavymetalionsfromwastewater.Theiradvantagesandlimitationsinappli-cationarealsoevaluated.*Correspondingauthor.E-mailaddress:[e-mail](F.Fu).ContentslistsavailableatScienceDirectJournalofEnvironmentalManagementjournalhomepage:
2010ElsevierLtd.Allrightsreserved.doi:10.1016/j.jenvman.2010.11.011JournalofEnvironmentalManagement92(2011)407e4182.Heavymetalwastewatertreatmenttechniques2.1.ChemicalprecipitationChemicalprecipitationiseffectiveandbyfarthemostwidelyusedprocessinindustry(KuandJung,2001)becauseitisrelativelysimpleandinexpensivetooperate.Inprecipitationprocesses,chemicalsreactwithheavymetalionstoforminsolubleprecipitates.Theformingprecipitatescanbeseparatedfromthewaterbysedimentationorfiltration.Andthetreatedwateristhendecantedandappropriatelydischargedorreused.Theconventionalchemicalprecipitationprocessesincludehydroxideprecipitationandsulfideprecipitation.2.1.1.HydroxideprecipitationThemostwidelyusedchemicalprecipitationtec