Fastremovalofmethylene

Fastremovalofmethylenebluefromaqueoussolutionbyadsorptionontochitosan-g-poly(acrylicacid)/attapulgitecompositeLiWanga,⁎,JunpingZhangb,AiqinWangb,⁎aCollegeofMaterialScienceandArtDesign,InnerMongoliaAgriculturalUniversity,Hohhot010018,ChinabCenterofEco-materialandGreenChemistry,LanzhouInstituteofChemicalPhysics,ChineseAcademyofSciences,Lanzhou730000,ChinaabstractarticleinfoArticlehistory:Received18February2010Receivedinrevisedform30June2010Accepted29July2010Availableonline25August2010Keywords:CompositesAttapulgiteChitosanAdsorptionMethyleneblueBatchadsorptionexperimentswerecarriedoutfortheremovalofmethyleneblue(MB)cationicdyefromaqueoussolutionusingchitosan-g-poly(acrylicacid)/attapulgitecomposites(CTS-g-PAA/APT)asadsorbent.Theeffectsofattapulgite(APT)content,initialpHvalueofthedyesolutionandtemperatureonadsorptionwereinvestigated.ResultsshowedthatAPTcontentofcompositeshadsomeinfluenceonadsorptioncapacities,andintroducingasmallamountofAPTcouldimproveadsorptioncapacityofchitosan-g-poly(acrylicacid)(CTS-g-PAA)toacertainextent.ResultsfromkineticexperimentaldatashowedthattheadsorptionrateofMBonCTS-g-PAAandCTS-g-PAA/APTwith30%ofAPTwasfast,andmorethan90%ofthemaximumadsorptioncapacitiesforMBwereachievedwithintheinitial15min.TheadsorptionbehaviorsofCTS-g-PAAandCTS-g-PAA/APTshowedthattheadsorptionkineticsandisothermswereingoodagreementwithapseudo-second-orderequationandtheLangmuirequation,andthemaximumadsorptioncapacitiesreached1873and1848mg/gforCTS-g-PAAandCTS-g-PAA/APT,respectively.ThediscussionresultsofthedesorptionstudiesimpliedthatCTS-g-PAAandCTS-g-PAA/APTcanbeusedaspromisingadsorbentsfortheremovalofMBfromwastewater.©2010ElsevierB.V.Allrightsreserved.1.IntroductionWastewatersfromindustriesliketextile,dying,printing,cos-metics,foodcoloring,papermaking,etc.arethemajorcontributorsofcoloredeffluents[1].Therearemorethan100,000commerciallyavailabledyeswithover7×105tonsofdyesproducedannually[2].Itisestimatedthat2%ofdyesproducedannuallyaredischargedineffluentfrommanufacturingoperations,while10%wasdischargedfromtextileandassociatedindustries[3].Dischargingofdyesintowaterresourceseveninasmallamountcanaffecttheaquaticlifeandfoodweb.Dyescanalsocauseallergicdermatitisandskinirritation.Someofthemhavebeenreportedtobecarcinogenicandmutagenicforaquaticorganismsandhumans[4–6].Methyleneblue(MB)isthemostcommonlyusedsubstancefordyingcotton,woodandsilk.MBcancauseeyeburnswhichmayberesponsibleforpermanentinjurytotheeyesofhumansandanimals.Oninhalation,itcangiverisetoshortperiodsofrapidordifficultbreathingwhileingestionthroughthemouthproducesaburningsensationandmaycausenausea,vomiting,profusesweating,mentalconfusionandmethemoglobinemia[7].Therefore,theremovalofMBfromwasteeffluentsbecomesenviron-mentallyimportant.Mostofthedyesarestabletophotodegradationandbiodegradation[8–10].Thus,coloredwastewaterposesachallengetotheconventionalwastewatertreatmenttechniques.Thusfar,manymethodssuchascoagulationandflocculation[11],membraneseparation[12],oxidationorozonation[13,14],electro-coagulation[15]andadsorption[16]havebeenutilizedforremovingdyes.Amongthem,adsorptionhasbeenfoundtobeaneffective,cheapandpotentialtechniqueforremovingdyesorotherinfectant[17],andmanydifferenttypesofadsorbentsweredevelopedandusedfortheeffectiveremovalofcolorfromaqueouseffluent.Inrecentyears,naturalpolymericmaterialshavedrawnconsiderableattentionbecausetheyarerenewable,biodegrad-able,non-toxicandpotentialasanenvironmentallyfriendlymaterial[18].Chitosan(CTS)istheN-deacetylatedderivativeofchitinandthesecondmostplentifulnaturalbiopolymer.Asawell-knownsorbent,CTSiswidelyusedfortheremovalofheavymetalsanddyes[19–21].However,CTScanonlyadsorbverysmallamountsofcationicdyesbecauseitisanaturalcationicpolysaccharide.Moreover,therelativelyhighmarketcostandlowspecificgravityalsolimiteditspracticaloperation.Recently,clayssuchasmontmorillonite[22–25],attapulgite[26,27],kaolin[28]andmica[29]aregaininginterestforapplicationasadsorbentsinwastewatertreatmentduetotheirlowcost.However,thedispersionandsuspensionabilitiesofclayinaqueoussolutionneedtobeimprovedforpracticaloperation.Therefore,severalattemptshavebeenmadetodevelopmoreeffectiveadsorbents.Hydrogelsareformedofthree-dimensionalcrosslinkedpolymernetworksofflexiblechains,whichareabletoabsorbandretainwaterDesalination266(2011)33–39⁎Correspondingauthors.L.WangistobecontactedatTel.:[phone].A.Wang,Tel.:[phone];fax:[phone].E-mailaddresses:[e-mail](L.Wang),[e-mail](A.Wang).0011-9164/$–seefrontmatter©2010ElsevierB.V.Allrightsreserved.doi:10.1016/j.desal.2010.07.065ContentslistsavailableatScienceDirectDesalinationjournalhomepage:[30].Ashydrogelspossessionicfunctionalgroupssuchascarboxylicacid,amine,hydroxylandsulfonicacidgroups,theycanabsorbandtrapmetalions[31,32]orcationicdyessuchasMB[33]fromwastewater.Therefore,thehydrogelsmaybeusedasanalternativeadsorbentfortheremovalofcationicdye