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2004April

    ;JOURNALOF

    ;TIANJINUNIVERSITYOFSCIENCEANDTECHNOLOGYVo1.19Supp ;USINGCoLLoIDALLAYERED

    ;DoUBLEHYDRoXIDES

    ;ASCATIoNIC

    ;MICRoPARTICULATE

    ;CoMPoNENT

    ;Son#inWang,WenxiaLiu

    ;ShandongInstituteofLightIndustry,Jinan250100, ;People’sRepublicofChina

    ;ABSTRACT

    ;Layereddoublehydroxidesconsistingoflayerswith ;cationicchargesmaybepotentialcandidatesof ;cationicmicroparticlesformingsynergeticretention ;effectwithanionicpolyacrylamide.Inthiswork,the ;layereddoublehydroxideswithvariousmolarratios ;ofMg/Alweresynthesizedbycoprecipitationof

    ;magnesiumchlorideandaluminumchlorideandpep. ;tizedbyintensewashingwithwater.Thechemical ;formula,particlesize,Zetapotentialofthelayered ;doublehydroxidewereanalyzed.Itwasfoundthat ;positivelychargedmagnesiumaluminumhydroxide ;withparticlediameterinnanoparticlesizecouldbe ;prepared.TheZetapotentialandparticlesizevary ;withthefeedmolarratioofMAlandthepeptizing ;process.respectively.TheZetapotentialisalsoPH ;dependent.Theretentionexperimentscarriedouton ;DDJshowthatwhenusedtogetherwithanionicpoly. ;acrylamide.thepositivelychargedcolloidaldouble ;hydroxidegreatlyimprovestheretentionofreed ;pulps.Thechemicalformula.particlesizeandZeta ;potentialofthecolloidaldoublehydroxidealla_ect

    ;itsretentionbehavior.

    ;KEYWORDS:layereddoublehydroxides,hydro- ;talcite,microparticle,retentionaid.

    -04 ;ArticleID:1672-6510(2004)supp-0305

    ;INTR0DUCT10N

    ;Microparticulateretentionaidsystemshavebeen

    ;widelyacceptedinpapermakingindustry.Thetypical ;microparticulatecomponentsincludeinorganiccol

    ;loidalsilica(orstructuredcolloidalsilicasol[11,mont. ;morillonite[2]andorganicmicropolymers[3].Theyare ;allnegativelychargedandformsynergicretentionef- ;fectswitl1eithercationicstarchorpolyaminoamide. ;Yet.itisinterestingtonotethatcationicmicroparti

    ;clesalsohavebeenfoundtobeeffectiveinfloeculat

    ;ingfinesolidsalongwithanionicorcationicpoly- ;mersH,

    ;.

    ;Cationicmicroparticlescanbesynthesized ;viaeitheremulsifierfleeemulsioncopolymerization

    ;_6]oremulsionormicroemulsioncopolymerizationr~. ;OvendenandXiao[evendevelopcationicnanoparti

    ;clesinfibrousshape.

    ;Layereddoublehydroxidesareclayswithpositive ;chargesasFig.1.Theyconsistofpositivelycharged ;layersandinterlayeranions.Thegeneralcomposition ;is[MlMx3(OH)2+Ax,mH20,[91

    ;whereMrepresentsadivalentcationg2+’Ca2+’

    ;Zn+etc),M3representsatrivalentcation,suchas ;A1+.Cr3An-representstheinterlayeranionwithn

    ;charge,andxisthelayercharge.Hydrotalciteisone ;ofthelayereddoublehydroxidesthatoccursinna- ;ture.Itconsistsofsheetsofoctahedralmagnesium/a

    ;luminumdoublehydroxides.Magnesium/aluminum ;doublehydroxidessharingtheiredges,inwhichthe ;positivelayerchargesarebalancedbycarbonateThe ;positivechargedlayersareformedanions,asshowed ;inFig.1.ThedivalentMandIrivalentA1cations ;occupythecentersoftheoetahedra.Theanionsto

    ;getherwithwatermoleculesarearrangedbetween ;layerstq”,2/,viaisomorphicallysubstitutionofM22+

    ;ionsinthecentersoftheoctahedrabVItsbal

    ;ancedanionscanbereplacedbyotheranionssuchas ;N01orCl’.Therefore.bycontrollingthereactingra—

    ;tioofMgandAlandincorporatingmonovalentan

    ;ionsinsteadofdivalentcarbonateintothelayersof ;hydrotalcite.positivelychargedmicroparticles,?itI1

    ;highZetapotentialsmaybeprepared.Sincehydrotal

    ;citecrystallizeeasily,thepropertiesofcolloidalmag- ;nesiumaluminumhydroxidewerenotextensivelyin

    ;vestigated.Asweknew,therewerenopublications

;abouttheapplicationofcolloidalmagnesiumalu

    ;minumhydroxideinflocculatingpaperfurnishes. ;Therefore,Theobjectivesofthisresearchweretoin

    ;vestigatethepossibilitiesofpreparingpositively ;chargedcolloidalmagnesiumaluminumhydroxide ;anduseitascationicmicroparticlecomponenttoim

    ;provefter

    ;thoroughlywashing,thepulpswerebeatento33.8.S ;inlaboratoryValleybeater.

    ;Chemicals:APAMwassuppliedbyCibaSpecialty ;ChemicalLtd.(moleculeweightwasabout8mil. ;1ions).Magnesiumaluminumhydroxideswerepre. ;paredbythecoprecipitationofmagnesiumandalu

    ;minurnchlorideatalkalinepH.

    ;Proceduresandequipments

    ;parationofMagnesiumaluminumhvdroxide ;Adesignedamountofmagnesiumchlorideandalu. ;minumchloridewasmixedanddissolvedin500ml ;deionizedwaterinatotalmetalconcentrationof ;O.5M.thendilutedammoniawater(volumeratioof ;5:l1wasaddedslowlytothesolutionatstirringuntil ;precipitatewasformedandthePHvaluewasupto ;9.5lO.O.Theprecipitatewasagedfordaysinits ;parentsolutionatroomtemperature,andthenpep

    ;tiziedatconstanttemperatureduringseveralwashing ;steps.

    ;CharacterizationofMagnesiumuminumhy. ;&oxide

    ;Thevolumeaverageparticlediametersofmagne. ;siumaluminumhydroxideweremeasuredusinga ;Mastersizer2000fMalvemInstrumentsLtd..UK)in ;aqueoussolution.The,一potentialwasdetermined

    ;usingaJS94Gmicroelectrophoresisanalyzerinaque. ;OUSsolutionsof0.0lMNaClatpH8.25.

    ;Stockpreparation

    ;Thereedpulpsweredisintegratedfor30o00revolu. ;tionsinGBJAStandardFiberDisintegratoratthe ;concentrationof1.5%.After2O%Oftalcpowder ;(basedontheweightofdryfiber)wasadded,the ;stockwasdilutedto0.5%.

    ;Dno371icretentionexperiment

    ;2%Ofmagnesiumaluminumhydroxidewasaddedto ;500mlofstockatastirringspeedof1000rpmand ;followedbycontinuousstirringfor30seconds.Then.

    ;0.1%APAMwasaddedandmixedforanother30 ;seconds.Finally.thecontentsintheDDJwerea1. ;1owedtodrainat750rpmbygravityandtheinitial ;1OOmloffiltratewascollected.Theretentionofstock ;wascalculatedaccordingtothereference[m. ;RESULTSANDDISCUSSION

    ;CharacterizationofMagnesiumduminumhydrox

    ;

    ;TableIistheZetapotentialsandparticlesizesof ;magnesiumaluminumhydroxidesinvariousfeed ;molarratiosofmagnesium|aluminum.Ascanbe ;seenthatallthesampleshavediametersinthesizeof ;nanoparticlesandbearcationiccharges.The(p0

    ;tentialsareincreasedwithincreasingthefeedratios ;ofmagnesiumandaluminum.buttheparticlediame

    ;tersdonotchangedremarkablyexceptforthesample ;with3:lmolarratioofM,Al+.

    ;Table1.ParticlediametersandZetapotentialofmagnesiumaluminumhydroxideswithvariousfeedrati

    osofMg/A1.

    ;Thecationsofmagnesiumaluminumhydroxideis ;composedofAl3andMg2whichoccupyitsoctahe. ;dralholesandrandomlydistributedwithinthesame ;hydrotalcitelayers[.AccordingtoLowensteinrule: ;Mg2+(OH)6octahedrasharingedgesareformallyneu

    ;tral,whileA1(0H)6octahedraareformallypositive ;monovalent;sothepresenceofAl(0Hoctahedra ;sharingedgeswouldberatherunstablebecauseof ;electricalrepulsion.Consequently.theminimum ;Mg2+/A1molarratiowouldbe2:linordertoavoid ;Al(0H)6octahedrasharingedges[.Whenmore ;306

    ;then2:lofMg2arereplacedbyAlgibbsiteAI ;(0H1wouldbecoexistwithhydrotalcitelikemag

    ;nesiumaluminumhydroxide[.whichwouldreduce ;thepermanentpositivechargesontheproducts.Yet. ;whythesamplewith3:lmolarratioofM+/Al ;showhigherZetapotentialandlargerparticlesize ;thanthatwith2:lmolarratioofM+/Al+sampleis ;notclear.Itmaybeattributedtoitshigherphasesta

    ;bilityandcrystallinitysinceitsmolarratioissimilar ;tothatofnaturalhydrotalcite.

    ;Thepeptizationofmagnesiumaluminumhydroxide ;

    ;Vo1.19SuppJournalofTianjinUniversityofScienceandTechnology

;dependsonits(potential,andtI1e(potentialin

    ;turndependsonthecontentsofmagnesiumionsin ;theprecipitate.Thehigher(potentialscause

    ;strongerrepulsionsamongcolloidalparticles.conse

    ;quently,thecoprecipitateofmagnesiumaluminum ;hydroxidesareeasiertobepeptized.Yet,theparticle ;sizeofthepeptizedmagnesiumaluminunlhydroxide ;seemstobeindependentofpeptizingprocess. ;Chemicalformulaof~siumaluminumhydrox

    ;ide

    ;Chemicalanalysiswasconductedforthecolloidal ;samplewithastartingmaterialinthemolarratioof ;l:lMg2+/A1_Thecorrespondingchemicalformulas ;is:

    ;M.9AI(OH)429(e1)0.1289nH20

    ;ItcanbeseenthatthemolarratioofMg2+/A1inthe ;finalproductsisslightlylowerthanthatofthestart

    ;ingmateria1.SomeofMg2inthecoprecipitatewas

    ;washedoutduringthepeptizingprocess. ;Electrophoreticproperties

    ;Fig.2displaysthej=potentialofmagnesiumalu

    ;minunlhydroxidewitl1l:lfeedratioofMg2,Alasa ;functionofsolutionPH.ThestartingpHofthecol

    ;loidaldoublehydroxideis8.Apparently.theZeta ;potentialsofmagnesiumaluminumhydroxidewere ;PHdependent.lenthecolloidaldoublehydroxide ;wasadjustedtolowerpHwithHC1,theM(OH)6 ;andAl(OHoctahedrawouldadsorbH+andbeal

    ;teredtopolycations.TheZetapotentialsofthesol ;areenhanced.OnlywhenmostoftI1edoublehydrox

    ;idedissolvedandreleasedasMandA1theZeta ;potentialisdecreased.enthepHwasadjustedto

    ;higherpHwithNaOH,partofAl(OH)6octahedra ;wouldbeprecipitatedasAl(OH)3.Theratioof ;Mg2linthedoublehydroxidelayersisincreased, ;whichresultsintheimprovementoftheZetapoten

    ;tia1.WithmoreNaOHbeingadded,theAl(OH)3is ;changedtoAlrOH)4-.TheZetapotentialofthecol

    ;loidaldoublehydroxidefallsdown.However,inthe ;generalpapermakingpHfromacidtoalkaline,the ;colloidalmagnesiumaluminumhydroxidebearscon

    ;siderablyhighpositivecharges.

    ;

    ;2.5

;ts

    ;10

    ;wereusedtoinvestigatetheretentioneffectofmag- ;nesiumaluminunlhydroxideonreedpulps.Allthe ;experimentsweredoneusingaDDJ.

    ;TheresultsinFig.3showthatmagnesiumaluminum ;hydroxidesolsCanremarkablyimprovethefurnish ;retentionwhenusedtogether,?itl1APAM.Theen

    ;hancementoffurnishretentioncanbereachedas ;hi25%.Themagnesiumaluminumhydroxidesols ;havesimilarparticlesizeswithvariousfeedmolarra

    ;tiosofMg/A1exceptforthesampleOf3:1.Thedifre

    ;enceofZetapotentialsisalsonotgreatenoughto ;causeanydiscrepanciesontheretentioneffectsof ;variousmagnesiumaluminumhydroxidesexceptfor ;samplewith3:lmolarratioofMg/AI.Therefore.we ;thinkthatthediscrepancyofthecolloidalmagnesium ;aluminumhydroxidewithvariousfeedratiosof ;MAlotherthantI1atof3:lonfurnishretentionare ;introducedneitherbyparticlesizenorbyZetapoten

    ;tia.

    ;?l

    ;Hj

    ;

    ;.

    ;【】一MIIg:

    :2:

    ;n.?一!一一

    ;??-

    ;I?g:

    :3:

    ;【】_IOl52O

    ;l(c=0.197%vo1)

    ;lig3I-~ffectofMg/AImolarratioonFPR ;FromFig.2wecanfindthatthecolloidalmagnesium ;aluminumhydroxideswithMg/Almolarratiosof3:1 ;and1:1showhigherimprovementsofretentionel- ;fectsonreedpulps.

    ;Effect0MagnesiumaluminumhydroxideJ)drt ;diameterson

    ;ForinvestigatingtheeffectofparticleSize,wepep

    ;tizedthemagnesiumaluminumhydroxidewitl1the ;feedMg/A1molarratioof1:1todifferentparticledi

    ;ameters.

;pH

    ;Fig.2ZetapotentialsofMMHasafunctionof ;solutionpH

    ;RetentionEffectof~lgnesiumaluminumhydrox

    ;ideonreedpulps

    ;Thecolloidalmagnesiumaluminumhydroxideswith ;variousMg/A1molarratiosinthestartingmaterials ;lIHl

    ;}

    ;:J

    ;?_I

    ;6fJ

    ;——

    ;?1f{

    ;

    ;_-._-2;

    ;0I52O

    ;,?llIl71)

    ;Fig74Efl’ectof,fariousMg/AIParticlediameterson ;一一

    ;l一一Particlediameters0.117um

    ;

    ;2Particlediameters0.678um

    ;Fig.4showstheresultsofthekretentioneffects.Ap

    ;parently,thecolloidalmagnesiumaluminumhydrox

    ;idewithsmallerparticlesizedisplayshigherreten

    ;tioneffect.Therefore.forthesamplewitl13:1feed ;molarratioofMg/A1,thehigherretentioneffectmust ;307

    ;

    ;JournalofTianjinUniversit)ScienceandTechnolo~Vo1.19Supp

    ;benefitfromitshigherZetapotentia1.Thus.wecan ;concludethatthechemica1formulaaswel1asparti

    ;clesizeandZetapotentialallaffecttheretentionbe. ;haviorofcolloidalmagnesiumaluminumhydroxide. ;Themagnesiumaluminumhydroxidewithfeed ;MAlmolarratioof3:1.whichissimilartothe ;Mg/AImolarratioofnaturalhydrotalcite.showsthe ;highestretentioneffectonreedpulps.HighZetapo

    ;tentialandlowparticlesizesarealsobeneficialto ;improvetheretentionbehaviorofthecolloidalmag

    ;nesiumaluminumhydroxide.

    ;C0NCLUS10NS

    ;CoUoidalmagnesiumaluminumhydroxidesvia

    ;coprecipitationofmagnesiumchlorideandwithvat- ;iousmolarratiosofMAlwerepreparedaluminum ;chloridefollowedbypeptizingthecoprecipitate

    ;throughintensewashing.Theparticlesizecanbe ;controlledbypeptization.Thechargeproperties ;hillydependonthemolarratioofMg/Alwhichis ;s”ghtlylowerthanthefeedratioofstartingmateria1.

    ;andthepHofthecolloidalsolution.Thepositive ;chargedcolloidalmagnesiumaluminumhydroxide ;canremarkablyimprovethefurnishretentionwhen ;usedtogetherwithanionicpolyacrylamide.Thepar

    ;ticlesize.Zetapotentialaswellasthechemicalforu

    ;laareallveryimportantfortheretentioneffectsofthe ;colloidaldoublehydroxide.

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