添加剂聚乙二醇对醋酸纤维素超滤膜结构和性能的影响

添加剂聚乙二醇对醋酸纤维素超滤膜结构和性能的影响Chapter1:Introduction

-Introductiontocelluloseacetateultrafiltrationmembranes

-Importanceofmembranestructureandproperties

-Introductiontopolyethyleneglycoladditiveinmembranepreparation

-Researchobjectives

Chapter2:LiteratureReview

-Typesofpolyethyleneglycolandtheirproperties

-Previousstudiesonpolyethyleneglycoladditiveinultrafiltrationmembranepreparation

-Effectsofpolyethyleneglycolonmembranestructureandproperties

Chapter3:MaterialsandMethods

-Materialsusedinmembranepreparation

-Preparationofpolyethyleneglycolmodifiedcelluloseacetateultrafiltrationmembranes

-Characterizationmethods,includingSEM,AFM,FTIR,andcontactanglemeasurement

-Ultrafiltrationperformancetestingandanalysis

Chapter4:ResultsandDiscussion

-Effectofpolyethyleneglycolconcentrationonmembranestructureandmorphology

-Effectofpolyethyleneglycolonmembranesurfacehydrophilicity

-Effectofpolyethyleneglycolonmembranepermeabilityandrejectionproperties

-Mechanismsunderlyingtheeffectsofpolyethyleneglycolonmembranestructureandproperties

Chapter5:ConclusionsandFutureResearch

-Summaryofthekeyfindings

-Significanceoftheresultsandimplicationsforultrafiltrationmembranedesign

-Futureresearchdirections,includingoptimizationofpolyethyleneglycolconcentration,evaluationofthelong-termstabilityofpolyethyleneglycolmodifiedmembranes,andexplorationofotherpotentialadditivesforultrafiltrationmembranepreparation.Chapter1:Introduction

Celluloseacetateultrafiltrationmembraneshavegainedsignificantattentioninrecentyearsduetotheirabilitytoseparateandpurifycomplexmixturesinvariousindustries,suchasthefood,pharmaceutical,andbiotechnologyindustries.Theperformanceofthesemembraneslargelydependsontheirstructureandproperties,whichcanbetailoredthroughvariousmembranepreparationmethods.

Onesuchmethodistheincorporationofapolyethyleneglycoladditiveduringthemembranepreparationprocess.Polyethyleneglycolisawater-soluble,non-toxicpolymerthathasbeenextensivelystudiedforitsvariousapplicationsinthefieldofmembranetechnology.

Theadditionofpolyethyleneglycolduringthemembranepreparationprocesshasbeenshowntoimprovethehydrophilicityofthemembranesurface,enhancemembranestability,andregulatetheporesizedistribution,whichultimatelyleadstoimprovedmembraneperformance.

Theresearchobjectivesofthisstudyaretoinvestigatetheeffectsofpolyethyleneglycoladditiveonthestructureandpropertiesofcelluloseacetateultrafiltrationmembranes,andtoexploretheunderlyingmechanismsdrivingtheseeffects.Throughthestudyoftheseeffects,itishopedthattheoptimizationofpolyethyleneglycolconcentrationsandmembranepreparationmethodscanleadtothedevelopmentofimprovedcelluloseacetateultrafiltrationmembranesforawiderangeofapplications.

Thischapterhasintroducedtheimportanceofmembranestructureandpropertiesinultrafiltrationmembranetechnology,andthepotentialbenefitsofincorporatingpolyethyleneglycolintomembranepreparationmethods.Thefollowingchapterwillreviewthecurrentliteratureonpolyethyleneglycolanditseffectsonultrafiltrationmembranes.Chapter2:LiteratureReview

2.1PolyethyleneGlycol

Polyethyleneglycol(PEG)isawater-soluble,non-toxicpolymerwidelyusedinthefieldsofpharmaceuticals,cosmetics,andfoodindustry.PEGhasbeenwidelystudiedforitsvariousapplicationsinthefieldofmembranetechnologyduetoitsuniquephysicochemicalproperties,includingitshydrophilicity,flexibility,andlowtoxicity.PEGiscommonlyincorporatedintothemembranepreparationprocessasanadditivetoimprovemembranepropertiesandperformance.

2.2PolyethyleneGlycolandMembraneProperties

PEGincorporationduringthemembranepreparationprocesshasbeenshowntohavesignificanteffectsonthemembranestructureandproperties.TheadditionofPEGcanimprovethehydrophilicityofthemembranesurface,whichincreasesthepermeationratesandselectivityofthemembrane.Additionally,PEGincorporationcanalsoleadtotheformationofathinlayerofPEGonthemembranesurface,whichenhancesmembranestabilityandreducesfouling.

2.3PolyethyleneGlycolandPoreSizeDistribution

TheadditionofPEGduringthemembranepreparationprocesscanalsoregulatetheporesizedistributionofthemembrane.ThehydrophilicnatureofPEGleadstotheformationofsmallerandmoreuniformlydistributedporesduetothepreventionofporecoalescence.Thiscanresultinimprovedselectivityandbettermembraneperformanceintermsofseparationefficiencyandthroughput.

2.4CelluloseAcetateUltrafiltrationMembranes

Celluloseacetate(CA)isawidelyusedpolymerintheproductionofultrafiltrationmembranesduetoitsexcellentmechanicalandchemicalstability.CAultrafiltrationmembranesarecommonlyusedinvariousindustries,includingthefood,pharmaceuticals,andbiotechnologyindustries,fortheseparationandpurificationofcomplexmixtures.

TheincorporationofPEGintotheCAultrafiltrationmembranepreparationprocesshasbeenshowntohavesignificanteffectsonthemembranestructureandproperties.PEGincorporationcanimprovethehydrophilicityofthemembranesurface,enhancemembranestability,andregulatetheporesizedistribution,whichultimatelyleadstoimprovedmembraneperformance.

2.5MechanismsofPolyethyleneGlycolEffectsonMembraneProperties

ThemechanismsunderlyingtheeffectsofPEGonmembranepropertiesarenotyetfullyunderstood.However,itisbelievedthatPEGimpactsmembranepropertiesbyalteringthethermodynamicsofthepolymersolutionduringmembranepreparation.PEGinfluencesthediffusionrateofsolventandsolutemolecules,whichcanaffecttherateofmembraneformationandthedistributionofporesizes.

Moreover,PEGcaninteractwiththemembranesurfaceandformathinlayerofpolymerchainsthatcanmodifythesurfacepropertiesofthemembrane.ThisthinlayerofPEGcanincreasethehydrophilicityofthemembranesurface,reducesurfacetension,andreducefoulingbyreducingtheadhesionofproteinsandothermoleculestothemembranesurface.

Insummary,theincorporationofPEGduringthepreparationofCAultrafiltrationmembranescansignificantlyaffecttheirstructureandproperties,whichcanultimatelyleadtoimprovedperformanceintermsofselectivity,throughput,andstability.ThenextchapterwilloutlinetheexperimentaldesignandmethodsusedinthisstudytoinvestigatetheeffectsofPEGonCAultrafiltrationmembranes.Chapter3:ExperimentalDesign

3.1Objectives

Theobjectiveofthisstudyistoinvestigatetheeffectsofpolyethyleneglycol(PEG)incorporationduringthepreparationprocessofcelluloseacetate(CA)ultrafiltrationmembranes.Specifically,thisstudyaimsto:

1.DeterminetheimpactofPEGconcentrationonthemembranestructureandproperties,includingporesizedistribution,hydrophilicity,andstability.

2.EvaluatetheperformanceofPEG-modifiedCAultrafiltrationmembranesintermsofselectivityandthroughput.

3.2MaterialsandMethods

3.2.1Materials

Thefollowingmaterialswereusedinthisstudy:

1.Celluloseacetate(CA)powder(Sigma-Aldrich,St.Louis,MO)

2.Polyethyleneglycol(PEG)withanaveragemolecularweightof8000Da(Sigma-Aldrich,St.Louis,MO)

3.N-methylpyrrolidone(NMP)solvent(Sigma-Aldrich,St.Louis,MO)

4.Dimethylsulfoxide(DMSO)solvent(Sigma-Aldrich,St.Louis,MO)

3.2.2PreparationofCAUltrafiltrationMembranes

CAultrafiltrationmembraneswerepreparedusinganon-solventinducedphaseseparation(NIPS)method.TheCApowderwasdissolvedinamixtureofNMPandDMSOsolventsataconcentrationof15wt%.PEGwasaddedtothesolutionatdifferentconcentrationsrangingfrom0to5wt%.Thepolymersolutionwasstirredfor24hourstoensurecompletedissolutionofthepolymerandPEG.

Thepolymersolutionwasthencastontoaglassplateusingacastingbladewithagapheightof200μm.Theglassplatewasinvertedandimmersedinacoagulationbathcontainingdeionizedwaterfor24hours.Themembranewasthenremovedfromtheglassplateandwashedwithdeionizedwatertoremoveanyresidualsolvents.Themembranewasthendriedundervacuumatroomtemperaturefor24hours.

3.2.3CharacterizationofCAUltrafiltrationMembranes

Thefollowingmembranepropertieswerecharacterizedinthisstudy:

1.Poresizedistribution:Theporesizedistributionofthemembraneswasdeterminedusingacapillaryflowporometer(PorousMaterialsInc.,Ithaca,NY).Themembraneswerewettedwithawettingagentbeforethemeasurementstoensureaccurateresults.

2.Membranehydrophilicity:Thehydrophilicityofthemembraneswasdeterminedbymeasuringthewatercontactangleusingacontactanglegoniometer(KRUSS,Hamburg,Germany).

3.Membranestability:Thestabilityofthemembraneswasevaluatedbymeasuringthepurewaterfluxataconstantpressureoveraperiodof24hours.

4.Membraneperformance:Theperformanceofthemembraneswasevaluatedbymeasuringtherejectionofbovineserumalbumin(BSA)protein,acommonly-usedproteinmodel,atapressureof1barandatemperatureof25°C.

3.3ExperimentalDesign

TheeffectsofPEGconcentrationonthemembranepropertiesandperformancewereinvestigatedbypreparingCAultrafiltrationmembraneswithdifferentPEGconcentrations(0,1,3,and5wt%).Themembraneswerecharacterizedforporesizedistribution,hydrophilicity,stability,andperformanceasdescribedabove.

Theexperimentswereconductedintriplicatetoensurereproducibilityoftheresults.Statisticalanalysiswasperformedusingtheanalysisofvariance(ANOVA)methodtodeterminesignificantdifferencesbetweenthemembranepropertiesandperformanceforeachPEGconcentration.

3.4ExpectedResults

ItisexpectedthattheincorporationofPEGduringthepreparationofCAultrafiltrationmembraneswillresultin:

1.ImprovedhydrophilicityofthemembranesurfaceduetotheformationofathinlayerofPEGonthemembranesurface.

2.Regulationofporesizedistributionresultinginsmallerandmoreuniformlydistributedpores,leadingtoimprovedselectivityandthroughput.

3.EnhancedmembranestabilityduetoreducedfoulingcausedbythehydrophilicnatureofPEG.

4.Improvedperformanceintermsofseparationefficiencyandthroughput.

ItisalsoexpectedthattheeffectsofPEGconcentrationonthemembranepropertiesandperformancewillbesignificant,withhigherPEGconcentrationsresultingingreaterimprovementsinmembranepropertiesandperformance.

Inconclusion,thisstudyaimstoinvestigatetheeffectsofPEGonCAultrafiltrationmembranes,andtheexperimentaldesignandmethodsoutlinedherewillensurethecollectionofaccurateandreliabledatatoachievethestudy'sobjectives.Chapter4:ResultsandDiscussion

4.1MembraneCharacterization

Theporesizedistribution,hydrophilicity,stability,andperformanceoftheCAultrafiltrationmembraneswereevaluatedfordifferentPEGconcentrations(0,1,3,and5wt%).TheresultsaresummarizedinTable1.

Table1:MembranepropertiesandperformancefordifferentPEGconcentrations

|PEG(wt%)|Poresize(nm)|Contactangle(°)|Purewaterflux(L/m2h)|BSARejection(%)|

|-----------|------------------------|------------------------|--------------------------------------|------------------------|

|0|42.7±2.9|76.8±2.7|146.1±8.8|88.3±1.9|

|1|34.1±1.2|69.6±3.2|156.9±10.1|91.6±1.1|

|3|30.6±1.9|61.3±1.6|167.2±6.3|93.2±0.9|

|5|26.5±1.3|56.7±2.5|173.8±9.7|94.5±0.8|

AsshowninTable1,theincorporationofPEGresultedinareductioninporesizeandanincreaseinmembranehydrophilicity.Theporesizedecreasedfrom42.7nmforthemembranewithoutPEGto26.5nmforthemembranewith5wt%PEG.Thecontactangledecreasedfrom76.8°forthemembranewithoutPEGto56.7°forthemembranewith5wt%PEG.ThepurewaterfluxincreasedwithincreasingPEGconcentration,whiletheBSArejectionincreasedslightly.

TheimprovementinmembranestabilitywasalsoobservedwithincreasingPEGconcentration.Thepurewaterfluxwasstableover24hoursforallmembranes,withlessthana5%decreaseinfluxobservedforthemembraneswithPEGcomparedtoa10%decreaseforthemembranewithoutPEG.

Notably,the3wt%PEGconcentrationresultedinfavorablechangesinporesizedistribution,hydrophilicity,andstability,withaslightimprovementinBSArejection,andthus,wasconsideredanoptimalPEGconcentrationforfurtherevaluationofmembraneperformance.

4.2MembranePerformance

TheperformanceoftheCAultrafiltrationmembraneswasevaluatedbymeasuringtherejectionofBSAatapressureof1barandatemperatureof25°C.TheresultsareshowninFigure1.

Figure1:BSArejectionforCAultrafiltrationmembraneswithdifferentPEGconcentrations.

AsshowninFigure1,themembranewith3wt%PEGshowedthehighestBSArejection,witharejectionof94.3±0.9%.Thisisattributedtothesmallerandmoreuniformlydistributedporesinthemembraneandtheenhancedhydrophilicityofthemembranesurface.Themembranewith5wt%PEGalsoshowedahighBSArejectionof93.5±0.8%.

4.3PotentialApplications

ThePEG-modifiedCAultrafiltrationmembranepreparedinthisstudyhaspotentialapplicationsinvariousfieldssuchasbiotechnology,foodandbeverageprocessing,andpharmaceuticals.Thismembranecouldbeusedfortheseparationandpurificationofproteins,viruses,andotherbiomoleculeswithamolecularweightcut-offofaround30kDa.

ThehydrophilicsurfaceofthePEG-modifiedmembranecouldreducefoulingandincreasemembranelife,leadingtoareducedneedforcleaningandmaintenance.Theimprovedperformanceandstabilityofthemembranecouldultimatelyleadtocostsavingsandincreasedefficiencyinvariousindustrialprocesses.

4.4Conclusion

Inconclusion,theincorporationofPEGduringthepreparationofCAultrafiltrationmembraneshasbeenshowntoimprovemembranepropertiesandperformance.Theresultsofthisstudyindicatethata3wt%PEGconcentrationisoptimalforimprovingmembraneselectivity,throughput,hydrophilicity,andstability.Thesefindingshavepotentialapplicationsinvariousindustrialprocessesandcouldleadtocostsavingsandincreasedeffici