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JournalofEnvironmentalSciences20(2008)379–384
Adsorptionofformaldehydevaporbyamine-functionalizedmesoporous
silicamaterials
SRISUDASaeung1,VIROTEBoonamnuayvitaya2,∗
1.TheJointGraduateSchoolofEnergyandEnvironment,KingMongkut’sUniversityofTechnologyThonburi,Bangkok10140,Thailand.E-mail:sasrisuda@yahoo.com2.DepartmentofChemicalEngineering,KingMongkut’sUniversityofTechnologyThonburi,Bangkok10140,Thailand
Received15May2007;revised5July2007;accepted8August2007
Abstract
Theamine-functionalizedmesoporoussilicamaterialswerepreparedviatheco-condensationreactionoftetraethoxysilaneandthreetypesoforganoalkoxysilanes:3-aminopropyl-trimethoxysilane,n-(2-aminoethyl)-3-aminopropyltrimethoxysilane,and3-(2-(2-aminoehtylamino)ethylamino)propyl-trimethoxysilane.Cetyltrimethylammoniumbromidewasusedasatemplateforformingpores.Specificsurfaceareaandporevolumeoftheamine-functionalizedmesoporoussilicamaterialsweredeterminedusingsurfaceareaandporesizeanalyzer.Fouriertransforminfrared(FTIR)spectroscopewasemployedforidentifyingthefunctionalgroupsonporesurface.Inaddition,theamine-functionalizedmesoporoussilicamaterialswereappliedasadsorbentsforadsorbingformaldehydevapor.FTIRspectrashowedtheevidenceofthereactionbetweenformaldehydemoleculesandaminegroupsonporesurfaceofadsorbents.TheequilibriumdataofformaldehydeadsorbedontheadsorbentswereanalyzedusingtheLangmuir,FreundlichandTemkinisotherm.Thesamplefunctionalizedfromn-(2-aminoethyl)-3-aminopropyltrimethoxysilaneshowedthehighestadsorptioncapacityowingtoitsaminegroupsandthelargeporediameter.
Keywords:adsorption;characterization;amine;formaldehyde
Introduction
Formaldehydeemittedfromthebuildingmaterialsand
householdproductsindustryisacolorlessandpungent-
smellinggas.Itcancauseaseriousairpollutionproblem.
Sourcesofformaldehydeinthehomeincludesomedec-
oratedmaterials,paintandbinderofsomecombination
furnitureandchemicalfibercarpet.Thus,itmaybe
presentinhighconcentrationbothindoorsandoutdoors.
Formaldehydecancausewateryeyesburningsensations
intheeyesandthroat,nauseaanddifficultyinbreathingin
somehumansexposedatelevatedlevels(above0.1ppmv).
EnvironmentProtectionAgency(USEPA)reportedthat
exposedtoformaldehydecancausecancerinanimalsand
maycausecancerinhumanbeings.
Thecarbonaceousadsorbentsweremostwidelyused
forremovingformaldehydefromatmosphere(Haiqinet
al.,2003;Krisztina,2005).Nevertheless,theformalde-
hydeisnotefficientlyremovedbytheactivatedcarbon.
Priortothiswork,ourgroupreportedtheadsorption
offormaldehydebytheadsorbentsderivedfromcoffee
activatedcarbons(Viroteetal.,2005)andmesoporous
silicamaterials.Theexperimentalresultsindicatedthatthe
adsorptioncapacityofmesoporoussilicamaterialismore
*Correspondingauthor.E-mail:virote.boo@kmutt.ac.th.than1g/g-adsorbentwhichisaroundthreetimeshigher
thanthatofactivatedcarbon.
Theorderedmesoporousmaterialssynthesizedviasol-
gelroutewerefirstlydiscoveredbymobilcompany
researchers(Becketal.,1992;Kresgeetal.,1992).The
orderedmesoporousmaterialswereknownforusingin
manyapplicationssuchascatalysts(Wangetal.,1999;
IsaandBrent,2005),adsorbents(Zhaoetal.,2000;Ghiaci
etal.,2004;LuandYan,2004)andsensor(Kumaranet
al.,2001;Baohongetal.,2003;Xuetal.,2005),andso
on.Inparticular,thefunctionalizedmesoporousmaterials
hasbeenpaidmoreattentionfortheapplicationinremoval
andrecoveryofmetalions(Liuetal.,2000;Nooneyet
al.,2001;Hee-Jungetal.,2004),inadsorptionoforganic
dyes(Wuetal.,2004),andinimmobilizationofenzymes
orprotein(Hanetal.,1999;Leietal.,2004;Yuriietal.,
2004;MariaandZhao,2004),thatallrelatetothesurface
functionalgroupswhichcanbeappropriatelymodified.
However,theapplicationofthehybridmesoporousma-
terialsinformaldehydeadsorptionhasnotbeenexplored
yet.Therefore,herewereportedthesynthesis,character-
izationandefficiencyofformaldehydeadsorbents.The
co-condensationmethodisusedtointroducetheorganic
groupsintothesilicanetwork.380SrisudaSaeungetal.Vol.20
1Experimental
1.1Materials
Tetraethoxysilane(Si–(OC2H5)4,TEOS)wasusedas
thesilicaprecursor.Thefunctionalgroupsonporesurface
ofadsorbentweregeneratedfromnon-hydrolysedligand
oftrifunctionalorganoalkoxysilanes(R–Si–(OR)3):3-
aminopropyltrimethoxysilaneorAPTMS),n-(2-amino-
ethyl)-3-amino-propyltrimethoxysilaneorAEAP)and3-
(2-(2-amino-ehtylamino)ethylamino)propyltrimethoxysi-
laneorAEEA).Thecationicsurfactant,cetyltrimethyl
ammoniumbromide(C16H33(CH3)3NBr,CTAB)wasused
astemplateorpore-formingagent.Formaldehydevapor
generatedbyformaldehydesolution(37%,W/W)wasused
asadsorbateinadsorptionexperiments.
1.2Synthesisofamine-functionalizedmesoporoussili-
camaterials
Thesynthesisprocessinvolvedmixingofknown
amountsofCTAB,ethanolanddeionizedwaterbystir-
ringfor30min.ThenTEOSandR–Si–(OR)3were
simultaneouslyaddedtothevigorouslystirredmix-