Effects of ultrasound on cross-flow ultrafiltration of skim milk: Characterization from macro-scale to nano-scale
Résumé
This studyinvestigateseffectsofultrasound(US)oncross-flow ultrafiltration ofskimmilkbymulti-scale
characterization,usingacustomdesigned “SAXS Cross-FlowUS-coupledFiltrationCell”. Thestudyof
flow propertiesofcaseinmicellesuspensionsshowsanevolutionoftheirrheologicalbehaviorfrom
Newtoniantoshear-thinninguntiltheemergenceofyieldstresswiththeincreaseofconcentration
(from 27gL 1 to 216gL 1). Theconcentrationprofiles duringcross-flow filtration ofskimmilkhave
been revealedforthe first timebyreal-time in-situ Small AngleX-rayScattering(SAXS)measurement.
Without anychangeofinternalstructureofcaseinmicellesandmembraneselectivity,theapplied
ultrasound (20kHz,2Wcm 2) leadstoasignificant increaseofpermeate flux arisingfromadisruption
of concentratedlayer.VaryingtheUSintensityfrom0.6Wcm 2 to 2.9Wcm 2 does notaffecttheUS
enhancement factor,whichhoweverdependsonthefeedconcentration.Infact,increaseoffeed
concentration inducestheformationofhighlycohesivefoulinglayerduring filtration thattheappliedUS
could hardlydisrupt.ResultsalsosuggestthatthepreventiveUSapplicationmodeispromisingsince
formation ofthereversiblefoulinglayerwasstronglylimitedinthismode.