Adsorption-of-Hydroxyl--and-Amino-Substituted-Aromatics-to-Carbon-Nanotubes

AdsorptionofHydroxyl-andAmino-SubstitutedAromaticstoCarbonNanotubesWEICHEN,†LINDUAN,†LILINWANG,†ANDDONGQIANGZHU*,‡CollegeofEnvironmentalScienceandEngineering/TianjinKeyLaboratoryofEnvironmentalRemediationandPollutionControl,NankaiUniversity,Tianjin300071,China,andStateKeyLaboratoryofPollutionControlandResourceReuse/SchooloftheEnvironment,NanjingUniversity,Jiangsu210093,ChinaReceivedMay16,2008.RevisedmanuscriptreceivedJuly20,2008.AcceptedJuly22,2008.Thecombinedeffectsofhydroxyl/aminofunctionalgroupsofaromaticsandsurfaceO-containinggroupsofcarbonnanotubesonadsorptionwereevaluated.Whennormalizedforhydro-phobicity,2,4-dichlorophenoland2-naphtholexhibitedagreateradsorptiveaffinitytocarbonnanotubesandgraphite(amodeladsorbentwithoutthesurfaceOfunctionality)thanstructurallysimilar1,3-dichlorobenzeneandnaphthalene,respectively,and1-naphthylamineexhibitedamuchgreateradsorptiveaffinitythanallothercompounds.ResultsofthepH-dependencyexperimentsfurtherindicatedthatthehydroxyl/aminofunctionalgroupsoftheadsorbatesandthesurfacepropertiesoftheadsorbentsplayedacombinationalroleindeterminingthesignificanceofthenonhydrophobicadsorptiveinteractions.Weproposethatthestrongadsorptiveinteractionbetweenhydroxyl-substitutedaromaticsandcarbonnanotubes/graphitewasmainlyduetotheelectron-donatingeffectofthehydroxylgroup,whichcausedastrongelectron-donor-acceptor(EDA)interactionbetweentheadsorbatesandtheπ-electron-depletedregionsonthegraphenesurfacesofcarbonnanotubesorgraphite.InadditiontotheEDAinteraction,Lewisacid-baseinteractionwaslikelyanextraimportantmechanismcontributingtothestrongadsorptionof1-naphthylamine,especiallyontheO-functionality-abundantcarbonnanotubes.Thefindingsofthepresentstudymighthavesignificantimplicationsforselectiveremovalofenvironmentalcontaminantswithcarbonnanotubes.IntroductionCarbonnanotubesareconsideredpromisingcandidatesformanyareasofnanotechnologicalapplications,includingspecialsorbentsinwatertreatmenttoremoverecalcitrantcontaminants(1,2).However,therapidgrowthinproduc