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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-