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Adsorption of Hg(II) from aqueous solution by ethylenediamine-modified magnetic

Desalination258(2010)41–47

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Desalination

journalhomepage:http://www.wendangxiazai.com/locate/desal

AdsorptionofHg(II)fromaqueoussolutionbyethylenediamine-modi edmagneticcrosslinkingchitosanmicrospheres

LiminZhou ,ZhirongLiu,JinhuiLiu,QunwuHuang

KeyLaboratoryofNuclearResourcesandEnvironment(EastChinaInstituteofTechnology),MinistryofEducation,XuefuRoadNo.56,Fuzhou,Jiangxi344000,China

articleinfoabstract

Inthiswork,weexaminedtheeffectsofvariousparameters,suchaspH,contacttime,initialconcentration,andtemperature,ontheadsorptionofHg(II)byethylenediamine-modi edmagneticcrosslinkingchitosanmicrospheres(EMCR).EMCRhadthediametersizerangeof80–250μm,averageporesizeof826nm,BETsurfaceareaof68.6m2/g,andsaturatedmagnetizationof15.4emu/g.ThemaximumuptakeofHg(II)wasrecordedatpH5.AtpH3,Hg(II)couldbeselectivelyseparatedfromCd(II),Pb(II),Zn(II),Cu(II),Ca(II),andMg(II).Equilibriumdatawere ttedwellwithLangmuirisothermswiththemaximumadsorptioncapacityof2.69mmol/gforHg(II).Bothkineticsandthermodynamicparametersoftheadsorptionprocesswereobtained.Thedataindicatedthatadsorptionprocesswasexothermicspontaneousreactionandkineticallyproceededaccordingtopseudo-second-ordermodel.Themetalion-loadedEMCRwereregeneratedwithanef ciencyofmorethan90%using0.02–0.1Mthiourea.

CrownCopyright©2010PublishedbyElsevierB.V.Allrightsreserved.

Articlehistory:

Received17October2009

Receivedinrevisedform24February2010Accepted25March2010

Availableonline27April2010Keywords:

ChitosanmicrosphereEthylenediamineBiosorption

MagneticadsorptionHeavymetalsWastetreatment

1.Introduction

Mercury(Hg)isoneofthemosttoxicheavymetalscommonlyfoundintheglobalenvironmentincludinglithosphere,hydrosphere,atmo-sphereandbiosphereanditstoxicnaturehasbeenknownforcenturies.Thetoxicityofmercurydependsstronglyonitsredoxstate[1].ThemosttoxicformofmercuryisthehighlyreactiveHg(II),whichbindstotheaminoacidcysteineinproteins.Incontrast,thedangerofelementalmercury(Hg°)andorgano-mercurycompoundsliesintheirtransportroutes.Symptomsofmercurypoisoningaremainlyneuronaldisordersbutalsodamagetothecardiovascularsystem,kidney,bones,etc.[2].ThethreemajorsourcesofHgemissionsarenatural,anthropogenicandre-emittedsources.Urbandischarges,agriculturalmaterials,miningandcombustionandindustrialdischargesaretheprincipalanthropogenicsourcesofHgpollutionintheenvironment[3].

InordertominimizetheadverseeffectsofHgintheenvironment,itisdesirableto ndwaystocaptureitbeforeitbecomesaproblem.Severaltechniquesareavailableforthisincludingchemicalprecip-itation,coagulation,ionexchange,chemicalreduction,membraneseparation,biologicaltreatment,solidphaseextraction,andadsorp-tion[4–6].Amongthemadsorptionisbyfarthemostversatileandwidelyused,andactivatedcarbonisthemostcommonlyusedsorbent[5].However,theuseofactivatedcarbonisexpensive,sotherehasbeenincreasedinterestintheuseofotheradsorbentmaterials,particularlylow-costadsorbents[7].Theuseofadsorbentscontaining

Correspondingauthor.Tel.:+867948258320;fax:+867948258265.E-mailaddress:minglzh@http://www.wendangxiazai.com(L.

Adsorption of Hg(II) from aqueous solution by ethylenediamine-modified magnetic

Zhou).

naturalpolymershasreceivedgreatattention,inparticularpoly-saccharidessuchaschitinandchitosan[8].

Theapplicationofmagneticadsorbenttechnologytosolveenvironmentalproblemshasreceivedconsiderableattentioninrecentyears[9–15].Magneticpropertiescouldbeimpartedtosorbentsfacilitatingtheirtrappingfromthemediumusingamagnetic eldcomparedtothecentrifugalmethods[9].Moreover,techniquesemployingmagnetismaremoreamenabletoautomation[10].Theseadsorbentshaveavarietyofsurfacefunctionalgroupswhichcanbetailoredforuseinspeci capplications.Poly(2-hydroxyethylmeth-acrylate)[13],poly(oxy-2,6-dimethyl-1,4-phenylene)[14],polyvinyl-butyral[15],andchitosan[9]aretypicaladsorbentswhichareusedindifferentapplications.

Chitosanisalinearpolysaccharidethatisprimarilycomposedofβ(1→4)linked2-amino-2-deoxy-D-glucopyranoseunits,andresidual2-acetamido-2-deoxy-D-glucopyranoseunits.Itisachemicalderiva-tiveobtainedbyalkalinedeacetylationofchitinandalsoitisfoundnaturallyinsomefungalcellwalls.Chitosanhasmanyusefulfeaturessuchashydrophilicity,biocompatibility,biodegradabilityandanti-bacterialproperty.Sinceitisharmlesstohumans,chitosaniswidelyusedinfoodandpharmaceuticalprocesses,medicalandagriculturaldrugs[8].Chitosanisalsowellknownasanexcellentbiosorbentformetalcationremovalinnear-neutralsolutions[16–18],sincetheaminoandhydroxylgroupspresentonchitosancanactaschelationsites.Itisnoteworthythatmetaladsorptionmayinvolvedifferentmechanisms(chelationversuselectrostaticattraction),dependingonsolutioncomposition,pH,andspeciationofthemetalions[17].

Oneusefulformofchitosanforuseasasorbentisthebeadsormicrospheres[16,19–21].Flakeandpowerformsofchitosanarenot

0011-9164/$–seefrontmatter.CrownCopyright©2010PublishedbyElsevierB.V.Allrightsreserved.doi:

Adsorption of Hg(II) from aqueous solution by ethylenediamine-modified magnetic

10.1016/j.desal.2010.03.051

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