Impactofgrapheneoxideonremovalofheavymetalsusingmi

ImpactofgrapheneoxideonremovalofheavymetalsusingmixedmatrixmembraneRakaMukherjee,PrasenjitBhunia,SirshenduDe⇑DepartmentofChemicalEngineering,IndianInstituteofTechnologyKharagpur,Kharagpur721302,Indiahighlights
MembranebecamemorehydrophilicandporouswithadditionofGO.
Above90%rejectionofCr,Cd,PbandCuwaseffectedbyMMM.
MembraneperformedbetterinbasicpH,lowpressureandflowrate.
In-situmembraneregenerationwaspossiblebyacidtreatment.graphicalabstract0204060801001201401601802002200204060801001201401601802002202401020304050609092949698100pH=6.4pH=6.7pH=3.5CuCdCrPbRejection(%)Time(min)Membrane:GO0.2TMP:690kPaCFR:20l/hRejectionofdifferentheavymetalpH=6.5GO0.5GO0.35GO0.2Adsorptioncapacity(mg/g)Equilibriumconc.(mg/l)ChromiumpH3.5GO0.1AdsorptionisothermofChromiumasnaturalpH(pH3.5)Discretepoints:experimentaldataLine:DatafittedinLangmuirisothermarticleinfoArticlehistory:Received16December2015Receivedinrevisedform1February2016Accepted5February2016Availableonline9February2016Keywords:GrapheneoxideMixedmatrixmembraneHeavymetalAdsorptionBreakthroughtimeRegenerationabstractThegrapheneoxide(GO)impregnatedmixedmatrixmembrane(MMM)waspreparedbynon-solventinducedphaseinversionmethod.MMMwascharacterizedintermsofmolecularweightcut-off,porosity,permeability,averageporesize,poresizedistribution,contactangle,zetapotentialandmechanicalstrength.Themembranebecamehighlypermeable,hydrophilicandchargedonadditionofGO.Thesur-facemorphologyandroughnesswerestudiedthroughscanningelectronandatomicforcemicroscopy.EfficacyofMMMforremovalofheavymetalswasexploredusingthedevelopedMMM.ItshowedhighadsorptioncapacityforPb2+(79mg/g),Cu2+(75mg/g),Cd2+(68mg/g)andCr6+(154mg/g)atnaturalpH,6.7,6.5,6.4and3.5,respectively.Thesteadystatepermeatefluxwasaround30l/m2hfor50mg/lfeedconcentrationat414kPatransmembranepressuredropand40l/hcrossflowrate.RejectionofPb,Cu,CdandCrwereinbetween90%and96%forvariousoperatingconditionsandthebreakthroughtimewasaround10hfordifferentmetalions.Themembranewasregeneratedin-situ,byacidicsolutionatpH5.5.
2016ElsevierB.V.Allrightsreserved.1.IntroductionGraphenehasbeenproposedasthe‘‘nextgenerationmaterial”owingtoitsremarkableelectronic,optical,andthermalproperties,chemicalandmechanicalstability,andlargesurfacearea[1].Chemicalstructureofgrapheneoxide(GO)isreportedasoxidizedgraphene,decoratedwithvariousoxygenatedfunctionalitiessuchashydroxy,epoxyonthebasalplaneandcarbonyl,carboxylicacidattheedges[2].ThesefunctionalitiesmaketheGOmoreversatileinapplicationorientedresearch.Throughthesharingoftheloneelectronpaironoxygen,itcanefficientlybindthemetaliontoformmetalcomplex[2],thereby,renderingitaneffectiveadsor-bentforremovalofheavymetalions[3].TherearesomerecentreportsdemonstratinghighadsorptionabilityofGOforCd(II)[2],Pb(II)[3]andCu(II)[4].Inspiteofhavinghighadsorptioneffi-ciency,GOhassomedisadvantages:(i)possibilityofleachingofGOnanoparticles,duetohighaffinitytowardswaterand(ii)highcostofsynthesis[3].Consideringtheabovechallenges,amixedmatrixmembrane(MMM)ofultrafiltration(UF)gradecanoffer
2016ElsevierB.V.Allrightsreserved.⇑Correspondingauthor.Tel.:[phone];fax:[phone].E-mailaddress:[e-mail](S.De).ChemicalEngineeringJournal292(2016)284–297ContentslistsavailableatScienceDirectChemicalEngineeringJournaljournalhomepage::(i)noleachingofGOnanoparticles;(ii)themembranecanbeeasilyregeneratedand(iii)astherequiredamountofGOisless,theprocesswillbecosteffective.GOimpreg-natedMMMisreportedusingN-methyl-2-pyrolidoneassolventfordesalination[5].However,themembranetechnologyutilizingthehighadsorptioncapacityofGOforheavymetalsremainsunexplored.Presenceofheavymetalsinaquaticenvironmentposesaseri-ousthreattotheecosystem.Heavymetals,likechromium(Cr),cadmium(Cd),copper(Cu)andlead(Pb)areamongthemostdan-gerouspollutantsaccordingtoEnvironmentalProtectionAgency[6].Thesemetalsareextremelytoxic,evenintraceamount[7].Industrialanddomesticworkflow,leachingineffluentsanddegra-dationofearthcastaresomeofthemajorsourcesofseverecon-taminationtowaterstream[8].Thecommontechniquesforremediationofheavymetalsincludechemicalprecipitation,elec-trodialysis,activatedcarbonadsorption,phyto-extraction,reverseosmosisandionexchange[9].Thesemethodshavevariousdisad-vantages,likegenerationofhighamountoftoxicsludgeandliquidwaste,lowthroughput,highenergyrequirement,necessityofpreandpostprocessingandhighoperatingcost,limitingtheirapplica-bility[10–12].Hence,thereisaneedforefficient,highthroughputandlowenergyintensivetechniqueforremovalofheavymetals.Ligandbasedanchoringnanomaterialshaveseveraladvantages,likehighadsorptioncapacity,selectivityandfastkinetics.How-ever,performanceofthesemesoporousadsorbentsduringcontin-uousoperationusingreallifeeffluent,leachingofnanoparticlesandtheirposttreatmentarenotyetstudiedwell[13–15].Beingphysicalseparationprocessandlessenergyintensive,membranetechnologycanaddressthisproblemadequately.Reverseosmosis(RO)ismostsuit