Bubble attachment to cellulose and silica surfaces of varied surface energies wetting transition and - Ketola et al. - Unknown - Unknow

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S1SupportingInformationBubbleattachmenttocelluloseandsilicasurfacesofvariedsurfaceenergies:wettingtransitionandimplicationsinfoamformingAnnikaE.Ketola,aWenchaoXiang,bTuomoHjelt,aHeikkiPajari,aTeklaTammelin,aOrlandoJ.Rojasb,candJukkaA.Ketojaaa:VTTTechnicalResearchCentreofFinlandLtd,P.O.Box1603,FI-40101Jyväskylä,Finland;b:DepartmentofBioproductsandBiosystems,SchoolofChemicalEngineering,AaltoUniversity,FI-00076Espoo,Finlandc:DepartmentsofChemical&BiologicalEngineering,2360EastMall;Chemistry,2036MainMall,andWoodScience,2424MainMall,TheUniversityofBritishColumbia,Vancouver,BCV6T1Z3,Canada*Correspondingauthor:jukka.ketoja@vtt.fiDeterminationsurfacetension(γ)isothermsofSDSusingthereversedpendantdrop(bubble)method.Thesurfacetension(γ)isothermsofsodiumdodecylsulfate(SDS)andSDSwithNaCl(0.01M)additionweredeterminedusinganopticalThetatensiometer(Attension,BiolinScientific,Espoo,Finland).TheThetaconsistsofacamera,asamplestage,aquartzcuvette(20×20mm)andahookedneedle(0.7176mm,stainlesssteel).Inthemeasurement,thecuvettewasfilledwiththesampleliquidandthehookedneedlewasimmersedinthesolution.Then,a4µlairbubblewascreatedonthetipofthehookedneedle(Fig.S1)anddeterminationofγwasperformedusingreversedpendantdropshapeanalysis,inwhichγisdefinedbythebubbleshape:

1S2?02(S1)?=∆??,?whereγisthesurfacetension,Δρisthedensitydifferencebetweenphases,gisthegravitationalconstant,R0istheradiusofthebubblecurvatureattheapex,andβisashapefactor.βcanbedefinedthroughtheYoung-Laplaceequationexpressedas3Dfirst-orderequations.Theexperimentswerecarriedoutinaregulatedatmosphereof23°Cand50%relativehumidity.SurfacetensionisothermsofSDS.Thesurfacetension(γ)isothermsofSDSwithandwithout0.01MNaCladditionmeasuredusingthebubblemethodareshowninFig.S1.TheincreaseinSDSconcentrationresultedinadecreaseinγuntilcriticalmicelleconcentration(CMC)wasreachedataround8mM.Accordingtotheliterature,theCMCofpureSDSis8.4mM,afterwhichγremainsatca.36mN/m(Fainermanetal.2010).Thebumpinsurfacetensionintherange5.0−8.0mMindicatesthepresenceofimpurities(e.g.dodecanol)inthesolutionsasaconsequenceofSDShydrolysis(Fainermanetal.2010;Linetal.1999).ThepresenceofNaClshiftedtheCMCtoca.4mMandtheeffectofimpuritieswassignificantlyreduced.Theincreasedvolumeofpositivecounterions(Na+)enhancesSDSadsorptiontotheair-liquidinterface,maskingtheeffectofimpuritiesanddecreasingtheCMC(Fainermanetal.2010).8070)60/mmN(50γ40300.505.0050.00SDS(mM)SDSSDS+0.01MNaClFigureS1.Surfacetension(γ)isothermsofpureSDSsolution(●)andSDSsolutionwith0.01MNaCladdition(○)measuredusingthecaptivebubblemethodafter10minstabilizationofthebubble.Errorbarsshowthestandarddeviation.

2S3SDSadsorptionattheair-waterinterface.TheadsorptionofSDSattheair-waterinterfacecanbecalculatedusingthesurfacetensionisothermandtheGibbsequation:???(S2)?=−2????whereτisthesurfactantconcentrationattheinterface(perunitsurface),Cisthesurfactantconcentrationinsolution,γissurfacetension,Tistemperature(K)andRisthegasconstant(8.31J/K·mol).TheSDSadsorptionisothermfortheair-waterinterfaceisshowninFig.S2.43)22mol/mτ(µ100246810SDS(mM)SDSSDSin0.01MNaClMetastablebubblesFigureS2.SDSadsorptionisotherm(τ,mol/m2)fortheair-waterinterfaceofpureSDSsolution(●)andSDSsolutionwith0.01MNaCladdition(○)calculatedusingtheSDSsurfacetensionisotherm(Fig.S1)andGibbsequation(Eq.S2).Arrowsindicateconcentrationsatwhichbubbleinteractionchangesfromclearattachmenttometastable.Modelsurfacecharacteristics.VariationinsurfaceroughnesswasdeterminedwithAFM(Fig.S3).Silica,TMSCandcellulosesurfaceswereverysmooth;roughnessvariationwasonly2nmforsilicasurfacesandTMSCand3nmforcellulose.ThepartiallydesilylatedTMSCsurface(θD=75°)hadthehighestroughnessvariationof12nmandformationofsphericalagglomerateswasobserved.

3S4a)Si-OHSi-CH3TMSCPDTMSCCelluloseRMS:0.4nm3.4nm4.4nm18.4nm1.5nm(1x1µm;z-scale,2nm)(1x1µm;z-scale,5nm)b)2.0c)8.01.04.0nm0.0nm0.0-1.0-4.0-2.0-8.00.01.02.03.04.05.00.01.02.03.04.05.0µmµmSi-OHSi-CH3PartlydesilylatedTMSCCelluloseTMSCFigureS3.a)AFMimagesofthemodelsurfaceswithcalculatedRMSvalues.b,c)Roughnessvariation(heightprofile)ofhydrophilic(Si-OH,blue)andhydrophobic(Si-CH3,black)silica,partiallydesilylatedTMSC(green),cellulose(orange)andTMSC(red)surface.

4S5SDSisothermsforadsorptiononthemodelsurfacesa)b)6080Si-OHSi-OH406020)0.7mM6-40∆f07.0mM20-2070.0mM∆D(1070.0mM07.0mM-400.7mM-60-200500100015002000250005001000150020002500Time(s)Time(s)c)d)6080CelluloseCellulose406020)6-40∆f00.7mM7.0mM20-2070.0mM∆D(1070.0mM7.0mM-4000.7mM-60-200500100015002000250005001000150020002500Time(s)Time(s)FigureS4.SDSisothermsforadsorptionona-b)hydrophilicsilica(Si-OH)andc-d)cellulosedeterminedwithQCM-D.SDShadconcentrationsof0.7,7.0and70.0mM.Dataisillustratedasathirdovertonenumber(n=3).∆fisthechangeinoscillationfrequencyinHz,and∆Disthedissipation.Norisingstepwasincludedinthemeasurement.TableS1.QCM-DdataforSDSadsorptionondifferentmodelsurfacesafter10minofstartingtheSDSfeed.0.7mMSDSSurfaceCA(°)∆f,600s∆D,600s∆m(ng/cm2)∆m(µmol/m2)h(nm)Si-OH10-1.00.005.90.200.05Si-CellOH25-1.70.0910.10.340.09Si-CH3100-2.40.0814.40.490.1393-18.336.90108.03.701.00Si-TMSC7.0mMSDS

5S6SurfaceCA(°)∆f,600s∆D,600s∆m(ng/cm2)∆m(µmol/m2)h(nm)Si-OH10-1.60.269.70.330.09Si-CellOH25-4.50.4826.50.900.25Si-CH3100-4.00.2623.60.800.22-16.17.395.03.200.88Si-TMSC9370.0mMSDSSurfaceCA(°)∆f,600s∆D,600s∆m(ng/cm2)∆m(µmol/m2)h(nm)Si-OH10-12.09.5970.82.410.66Si-CellOH25-18.64.95109.93.741.02Si-CH3100-24.39.74143.64.881.3341.738.5-246.0-8.40-2.28Si-TMSC93Bubbleadhesiononpartiallyregeneratedcellulose.EventhoughbubblesdidnotpermanentlyattachtothesurfacewhenθDwasabout65°orbelow(inwater),therewasclearadhesiontothesurfacewhenthebubblewasremoved.Fig.S5showsbubbleelongationduringretractionfromthesurface.Inthesecases,thebubbleadhesiontotheneedlewasstrongerthantheadhesiontothesurface.AtaθDof65°(inwater)theelongationwasover500µmbeforedetachment.Adhesiontothesurfacedecreasedasthesurfacehydrophobicitydecreased,andwithpurecellulosesurfacestheadhesionwasnegligible.Also,thepresenceofSDS(1.0mM)decreasedtheadhesiontonegligiblevalues.Theeffectoftheneedleonbubblebehaviorisanunfortunatedrawbackofthecaptivebubblemethodusedinthisstudy.Bubblesareknowntoattachreadilytomineralparticles,suchasmolybdenite,graphite,withmoderatehydrophobicity(θD=60°−70°),showingthesamevaluesforθBand100%attachmentprobability.Modificationofthesurfaceswithdepressants,likexanthangumandCMC,decreasebothθB(40°−50°)andtheattachmentprobabilityandthetimescaleofwettingfilmrupture(Koretal.2014;Krasowskaetal.2019;Wuetal.2015).Itispossiblethatpartlyregeneratedcellulosewithmoderatehydrophobicitywouldshowasimilarlowattachmentprobabilityiffreebubblesandalongenoughstabilizationtimeforthefilmruptureareused.Inthisstudy,onlyfullyattachedbubbleswereconsideredinthetheoreticalcalculations.

6S7600400200Bubbleelongation(µm)01009080706050403020θDwater,72.8mN/m1.0mMSDS,65mN/m2.4mMSDS,50mN/mFigureS5.Bubbleelongationduringremovalfromthesurfaceasafunctionofsurfacedropcontactangle(sessiledrop,θD).Si-TMSCandpartiallyregeneratedTMSCsurfacesmeasuredwithwater(blackdiamond),1.0mMofSDS(whitediamond)and2.4mMofSDS(greydiamond).Changesininterfaceandsurfaceenergiesduetoanattachingbubble.Thevariousenergycomponentsaffectedbybubbleattachmentincludetheliquid-vapor(LV)interfaceenergyofthebubble,thesolid-liquid(SL)energy,andthesolid-vapor(SV)energy.Below,weanalyzethedifferentenergycomponentsindetailanddevelopanequationforthetotalenergychangeinbubbleattachment(Gualda&Ghiorso2007).Ouranalysisincludesonlythesurfaceenergycomponentsandnot,forexample,anyelectricalenergyrelatedtothechargespresentinthesystem.BubbleinterfaceenergyFig.S6showsthegeometryofanattachedbubble.Iftheradiusofthesphereisr,andtheheightofthecapish,thenthevolumeofthesphericalcapis?ℎ2(S3)????=(3?−ℎ)3andthecurvedsurfaceareaofthesphericalcapis????=2??ℎ(S4)

7S8Bygeometry,ℎ=?(1−????)(S5)haθrFigureS6.Geometryofanattachedbubble.Whenabubbleattachestoasurface,theairvolume??ofthebubbleremainsroughlyconstant.Inotherwords,43(S6)??=??−????3UsingEqs.(S3)and(S5),Eq.(S6)canbewrittenas43?ℎ2??22??3??=??−(3?−ℎ)=[4?−?(1−????)(2+????)]=?(?)(S7)3333where?(?)=4−(1−????)2(2+????)=2+3????−???3?(S8)Thus,(S9)33???=√??(?)Theinterfaceareaoftheattachedbubbleis?=4??2−?=2??2(1+cos?)(S10)?????ℎ?????

8S9Thebubbleradiusofthefreebubbleis(S11)33????=√4?anditsinterfaceareais?=4??2(S12)??Thereductioninbubbleinterfaceenergyduetoattachmentonasurfaceis3?2/3∆?=?(?−?)=??(?)[41/3−2?(?)−2/3(1+????)]????????(S13)where?istheliquid-vaporsurfacetension.SolidsurfaceenergychangeOtherenergychangesarerelatedtothesurfaceenergiesatthebubble-solidcontact.Thecontactareaisgivenby?=??2???2?(S14)????Whenthebubbleattachestothesolidsurface,thereductioninthesurfaceenergyis∆?????=?????(???−???)(S15)Moreover,duringdewettingthesurfaceenergiessatisfy(Makkonen2017)???=2???−?cos(??)(S16)where??istherecedingcontactangle,whichforabubbleattachmentagreeswith?.FromEqs.(S9)and(S14−16)weobtain23??32))(S17)∆?????=?()????(???−γcos(????(?)Thetheoreticaltotalenergyreductionoftheattachedbubble(∆????)isobtainedbysummingupEqs.(S13)and(S17):23?122(S18)?3−2−2∆????=?(){?[43−?(?)3(2+????(2+????))]+????(?)3????}?

9S10TheeffectofSDSconcentrationandsurfacetensionontheΔEtotfrombubbleattachmenttonon-attachmentisshowninFigS7.Inwater,ΔEtotwas208nJ,andtheadditionofSDSdecreasedthisvalue.AsteepdecreaseinΔEtotoccurredaftercSDSof3.5mM(γ=45mN/m),whentheair-waterinterfaceisalmostfullycoveredwithSDS(Fig.S2)andhemimicellesformontheSi-CH3surface.AfterΔEtotof45nJatγ=40mN/m(cSDS≈CMC)nobubbleattachmentoccurred,andthesystemhadreacheditsenergyminimum.250200)nJ150(tot∆E100500807060504030γ(mN/m)SDSSDS+0.01MNaClFigureS7.Experimentaltransitionfromnon-attachmenttoattachmentasafunctionoftotalsurfaceenergyofthesystem(ΔEtot)andsurfacetension(γ).ReferencesFainerman,V.B.etal.(2010)“SurfaceTensionIsotherms,AdsorptionDynamicsandDilationalVisco-ElasticityofSodiumDodecylSulphateSolutions.”ColloidsSurf.A:Physicochem.Eng.Aspects354(1–3):8–15.Gualda,G.A.R.andGhiorso,M.S.(2007)“MagnetiteScavengingandtheBuoyancyofBubblesinMagmas.Part2:EnergeticsofCrystal-BubbleAttachmentinMagmas.”ContributionstoMineralogyandPetrology154(4):479–490.http://link.springer.com/10.1007/s00410-007-0206-8.Johansson,L.-S.etal.(2011)“ExperimentalEvidenceonMediumDrivenCelluloseSurface

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