Biosorption of Pb2+ by original and protonated citrus peels Equilibrium kinetics and mechanism.docx
- 文档编号:11896845
- 上传时间:2023-04-08
- 格式:DOCX
- 页数:27
- 大小:61.45KB
Biosorption of Pb2+ by original and protonated citrus peels Equilibrium kinetics and mechanism.docx
《Biosorption of Pb2+ by original and protonated citrus peels Equilibrium kinetics and mechanism.docx》由会员分享,可在线阅读,更多相关《Biosorption of Pb2+ by original and protonated citrus peels Equilibrium kinetics and mechanism.docx(27页珍藏版)》请在冰豆网上搜索。
BiosorptionofPb2+byoriginalandprotonatedcitruspeelsEquilibriumkineticsandmechanism
BiosorptionofPb2+byoriginalandprotonatedcitruspeels:
Equilibrium,kinetics,andmechanism
SilkeSchiewer
a,
andAnkitBalaria1,a
aDepartmentofCivil&EnvironmentalEngineering,UniversityofAlaskaFairbanks,POBox755900,Fairbanks,AK99775,USA
Received1December2007;
revised20May2008;
accepted23May2008.
Availableonline4June2008.
Abstract
Biosorptioncanbeanefficientlow-costprocesstoremovetoxicheavymetalsfromwastewater.ThisstudyinvestigatedtheuptakeofPb2+byprocessedorangepeels,apectin-richbyproductofthefruitjuiceindustry.Potentiometrictitrationsshowedasignificantlyhighernegativesurfacechargeofprotonatedpeelscomparedtooriginalpeels,withacidicgroupsaroundpH4,6,and10.FTIRspectraofpeelsweresimilartothoseofpectin.Thecarboxylicgrouppeakshiftedfrom1636to1645 cm−1afterPb2+binding,indicatedtheinvolvementofcarboxylgroupsinPb2binding.Dependingontheparticlesize,equilibriumwasachievedin30 minto2 h.Thefirst-ordermodelwasinferiortosecond-orthird-ordermodels.Theobtainedrateconstantsweremuchhigherforsmallerparticles,whilethecapacitywassimilarforallsizes.LowpH,increasedionicstrength,orcompetingco-ionsreducedPb2+bindingatlowsorbentdosages,butathighsorbentdosagesremovalremainedabove90%.ThePb2+uptakeat300 ppmwas2 mmol/g(40%ofthedryweight).Duetohighuptake,favorablekineticsandgoodstability,citruspeelbiosorbentsholdhighpromiseforindustrialapplications.
Keywords:
Biosorption;Heavymetals;Kinetics;FTIR;Titration;Mechanism
ArticleOutline
1.Introduction
1.1.Sorbentselection
1.2.Characterizationofsorbentfunctionalgroups
1.3.Kineticstudies
1.4.Effectsofenvironmentalconditions
1.5.Biosorptionisotherms
1.6.Objectives
2.Materialsandmethods
2.1.Materials
2.2.Potentiometrictitrations
2.3.FTIRexperiments
2.4.Lead-bindingexperiments:
generalconditions
2.5.Kineticexperiments
2.6.Effectofenvironmentalconditions
2.7.Isotherms
2.8.Modelingerroranalysis
3.Resultsanddiscussion
3.1.Characterizationofsorbentchargebypotentiometrictitration
3.2.FTIRcharacterizationoffunctionalgroupsandtheircontributiontometalbinding
3.3.Batchkinetics
3.4.Effectofenvironmentalconditions
3.5.Biosorptionisotherm
3.6.pHvariabilityduringadsorption
4.Conclusions
Acknowledgements
References
1.Introduction
PollutionofsurfacewatersbytoxicheavymetalssuchasPbfromindustrialsourcesandstormwaterrunoffisanimportantenvironmentalproblem.Totreatlargevolumesofwastestreams,forexamplefromminingoperations,cost-efficientprocessesarerequired.Biosorptionisapromisingtechniqueforthispurpose[1],especiallyiflow-costbiosorbentsbasedonbyproductsofotherindustriesareused.
1.1.Sorbentselection
Theeffectivenessofbiosorbentsdependstoalargeextentontheirbiochemicalcomposition,particularlyonfunctionalgroupsavailableincellwallpolysaccharides.Carboxylgroupscanplayanimportantroleinmetalbiosorptionbyalgalbiosorbents[2].Pectin,acellwallpolysaccharideofhigherplants,isbasedmainlyongalacturonicacid,featuresalargenumberofcarboxylgroups,andhasaknownabilitytobinddivalentcations[3]and[4].Therefore,pectin-richmaterialssuchascitruspeels,fromwhichpectiniscommerciallyextracted,haveahighpotentialformetalbinding.Anumberofpectin-richbyproductshavebeenstudiedfortheirmetal-bindingabilitiesincludingapplewaste[5]and[6],sugarbeetpulp[7],[8]and[9],orangepeels[10],[11],[12],[13]and[14],orangeandbananapeels[15],citruspeelsandcoffeehusks[16],anddifferentfruitmaterials,suchasseveraltypesofcitruspeel[17].Inthepresentwork,aprocessedcitruspeelproductwasutilizedforbiosorptionofPb2+becauseofthehighpectincontentofcitruspeels.
1.2.Characterizationofsorbentfunctionalgroups
PotentiometrictitrationcanbeusedtoevaluatethechargeofsorbentparticlesatdifferentpHvaluesbasedontheelectroneutralityequationofthesolution[18].ThismethodhasbeenusedtocharacterizepKavaluesofthefunctionalgroupspresentinbiosorbentssuchasbrownseaweeds[19],sugarbeetpulp[9],andprotonatedpectinpeelsfromfruitjuiceproduction[20].Tocomplementinformationfrompotentiometrictitrations,Fouriertransforminfrared(FTIR)spectroscopycanbeusedtocharacterizethefunctionalgroupsofbiomaterials,asdonefordifferentkindsofpectin[21],[22]and[23].Incontrasttocompoundssuchaspectinoroilsextractedfrompeels,verylittleFTIRresearchhasbeenreportedforwholecitruspeels.Perez-Marinetal.[13]characterizedorangepeelsbyFTIR,howevertheinterpretationwasvagueandinconclusive.
1.3.Kineticstudies
Thoughavarietyofmodelscanbeappliedtodescribebiosorptionkinetics[24],thosemostcommonlyusedarepseudo-first-orderandpseudo-second-ordermodels.Ajmaletal.[10]studiedkineticsofNisorptionbyorangepeelsandmodeledtherateusingfirst-orderkineticswithmaximumsorptionachievedinapproximately2 h.Withoutcomparingdifferentmodels,Lietal.[12]andXuanetal.[25]concludedthatafirst-ordermodelfitforCdandPbsorption,respectively,tochemicallymodifiedorangepeels.Reddadetal.[9]foundthatasecond-orderratemodelfitswellforkineticsofNi2+andCu2+biosorptionbypectin-richsugarbeetpulp.SchiewerandPatil[17]determinedthatasecond-ordermodelfitbetterthanafirst-ordermodelforbiosorptionofCd2+byprotonatedpectinpeels.Perez-Marinetal.[13]comparedapseudo-first-ordermodel,apseudo-second-ordermodel,theElovichequation[26],andasimpleexpressionforintraparticlediffusion,andfoundtheElovichequationbestdescribedCdsorptionbyorangepeels.Thecontradictoryresultsfoundintheliteraturenecessitatefurtherstudyofsuitablekineticmodelsforbiosorptionbycitruspeels.Furthermore,studiesonbiosorptionkineticsofcitruspeelsorrelatedmaterialshavesofarbeenconfinedtosimplefirst-andsecond-orderkineticmodels.Otherrateexpressionsshouldbetakenintoconsideration.
1.4.Effectsofenvironmentalconditions
BiosorptionofmetalionsdependsonparameterssuchaspH,temperature,ionicstrength,metalconcentration,co-ionpresence,andsorbentproperties.Annaduraietal.[15]foundthatuptakeofPb2+,Ni2+,Zn2+,Cu2+,andCo2+increaseswithpHduetocompetitionofmetalionswithprotonsatlowerpHvalues.LeeandYang[5]determinedthatCu2+bindingbypectin-richapplewastewashighestatpH5.5–7.5.Cusorptionwasonlyslightlyaffectedbyionicstrengthupto0.1N,butdecreasedathigherionicstrengthorinthepresenceofcompetingco-ionsNi2+andespeciallyPb2+.Apparentlymonovalentionshavelittleimpactonmetalbinding,whereasmorestronglybounddivalentcompetingionscanreducebindingofthetargetmetal.Pbisoftenoneofthemoststronglyboundionsinbiosorption.Therefore,thequestionariseswhetherPbbiosorptionbycitruspeelsissimilarlyaffectedbytheseparameters.
1.5.Biosorptionisotherms
Biosorptionisothermsareusefulinquantitativelyevaluatingandpredictingtheprocessperformanceofthebindingcapacityandaffinityfordifferentmetalconcentrationsandsorbentdosages.TheLangmuirandFreundlichisothermsaremostcommonlyusedduetotheirsimplicityandeaseofinterpretation.Annaduraietal.[15]foundthattheFreundlichmodelfitbetterthantheLangmuirmodelforbiosorptionofCu2+,Co2+,Ni2+,Zn2+,andPb2+onbananaandorangepeels.Jumleetal.[16]werealsoabletofitthesorptionofHg2+,Pb2+,andZn2+ionsbycitruspeelsandcoffeehusksusingtheFreundlichisothermmodel.SchiewerandPatil[17]foundsimilarlygoodfitsofLangmuirandFreundlichisothermsforCdbindingbylemon,orange,andgrapefruitpeelsatpH3andpH5;someisothermdataatpH5,however,didnotmatcheithermodel.UsingtheLangmuirisotherm,Reddadetal.[9]modeledbiosorptionofNi2+andCu2+ionsonsugarbeetpulpandobtainedagoodfitofthedata.Perez-Marinetal.[13]foundthattheSipsisothermfitbestforCdsorptionbyorangepeels,followedbyRedlich-Peterson,Langmuir,andFreundlichisotherms.ItisnotsurprisingthattheSipsmodelfitbestsinceithasanadditionalfittingparametercomparedtotheLangmuirmodel,whichitotherwiseresembles.
1.6.Objectives
TheobjectivesofthisresearchweretocharacterizethesurfacechargeandfunctionalgroupsinvolvedinmetalbindingofcitruspeelsorbentsbypotentiometrictitrationsandFTIRspectroscopy.DifferentkineticmodelswerecomparedfortheirabilitytodescribePb2+bindingbycitruspeels.TheeffectofenvironmentalconditionssuchaspH,co-ions,andionicstrengthonoverallbindingbycitruspeelswasstudied,andtheeffectofmetalconcentrationwasdescribedbysorptionisotherms.FurtherinformationaboutthebindingmechanismwasobtainedfromchangesinpHduringincrementaladditionofPb2+tocitruspeelsuspensions.
2.Materialsandmethods
2.1.Materials
Driedandgroundprocessedorangepeels(Valencia)weresuppliedbyRobertJonesofAlarmaConsultingCorporationinFlorida.Thesepeelsweresievedintodifferentsizefractions.Formostexperiments,originaluntreatedpeelswereused;however,pHtitrationsandFTIRstudieswerealsoperformedwithprotonatedpeels.Protonationwascarriedoutbysuspendingthesorbentmaterialin0.1 MHNO3(10 gofpeels/L)for3 h,rinsingwithdouble-deionizedwater,anddryingfor12 hat40 °C,inordertoremove
- 配套讲稿:
如PPT文件的首页显示word图标,表示该PPT已包含配套word讲稿。双击word图标可打开word文档。
- 特殊限制:
部分文档作品中含有的国旗、国徽等图片,仅作为作品整体效果示例展示,禁止商用。设计者仅对作品中独创性部分享有著作权。
- 关 键 词:
- Biosorption of Pb2+ by original and protonated citrus peels Equilibrium kinetics mechanism Pb2
链接地址:https://www.bdocx.com/doc/11896845.html