正渗透原理及浓差极化现象

22520105PROGRESSINCHEMISTRYVol.22No.5May20102009820099*973No.2009CB623402No.38901120[e-mail]@njut.edu.cn*1112121.2100092.266003。。O645.14A1005-281X201005-0812-10ForwardOsmosisandConcentrationPolarizationLiGang1LiXuemei1LiuYue1WangDuo2HeTao1GaoCongjie21.CollegeofChemistryandChemicalEngineeringKeyLabofMaterials-OrientedChemicalEngineeringNanjingUniversityofTechnologyNanjing210009China2.CollegeofChemistryandChemicalEngineeringOceanUniversityofChinaQingdao266003ChinaAbstractThebasisofforwardosmosisFOaswellastheprincipleofpressureretardedosmosisPROareintroducedandcomparedwithreverseosmosisRO.ThephenomenonandtheorythatactualpermeabilityinFOisfarbelowtheoreticalpermeabilityaredescribed.Themodelsdescribingtheconcentrationpolarizationinasymmetricmembranesaresummarized.Severalmethodsareintroducedtodecreasetheexternalconcentrationpolarization.Approachestoattenuatetheinternalconcentrationpolarizationbasedonthestructuredesignofmembranematerialsarepresented.ThereviewprovidesatheoreticalbasisforpreparationandapplicationofFOmembranematerials.KeywordsforwardosmosisreverseosmosispressureretardedosmosisinternalconcentrationpolarizationexternalconcentrationpolarizationContents1Introduction2Basicprincipleofforwardosmosis3Thephenomenonofconcentrationpolarization3.1Externalconcentrationpolarization3.2Internalconcentrationpolarization3.3Modelingconcentrationpolarization4Summary1、。。10235·813·202535。2.8m32220m31/4。3001。1m31.5—2.5kW·h5—10。、。forwardosmosisFO20.84kW·h/m372.1%3。、200。osmoticpower。19534。1655TW·h/5。pressureretardedosmosisPRO———2.6MPareversedelectrodialysis———6。PRO。37859—111213。14—16。1417—19。2021。。2009973———“”。FO。2223。2FO。1a。Δp=ΔΠ。1aFObPROcROFig.1SchematicofworkingprinciplesforaFObPROandcRO22。1886ΠV=iRT1i1ΠVRT。0.5M25atm。ΔpΔpΔΠRO1c。24Jw=AΔp－ΔΠ2JwAΔΠΔp。ΔpΔΠJw·814·22PRO1bΔp=0JwFO1a。Lee252。2、。Δp=0022Fig.2IllustrationsofprofilesfortherelationshipbetweenwaterfluxandappliedpressureinFOPROandRO.FOtakesplacewhenthehydraulicpressuredifferenceiszero.ThePROzoneiswheretheappliedpressuredifferenceisbetweenzeroandthefluxreversalpointandtheROzoneissituatedwheretheappliedpressuredifferenceisgreaterthantheosmoticpressuredifference22。ΔpΔΠ。22。、ΔΠ。ΔpΔΠ。ΔΠ1。。2、。。3。75%35%—50%26。4PRO。5、、。3252728。FO3。。3。abc。CΔΠeffFig.3IllustrationsofconcentrationpolarizationprofilesfordifferentmembraneorientationsinforwardosmosisprocessaAsymmetricdensemembrane.bAnasymmetricmembranewiththeporoussupportlayerfacingthefeedsolutiontheprofileillustratesconcentrativeinternalCP.cAnasymmetricmembranewiththeporoussupportlayerfacingthedrawsolutiontheprofileillustratesdilutiveinternalCP.CrepresentsthesoluteconcentrationΔΠeffrepresentstheeffectivedrivingforce3.15·815·4。。4。Fig.4Illustrationofexternalconcentrationpolarization.Thesolidlinerepresentssoluteconcentrationatdifferentposition.Thedottedlinerepresentsboundarylayerofconcentrationpolarization3aCFmCFbΠFmΠFbΔΠeff。CDmCDbΠDmΠDb。。。3.2。3bc。。FO。3bCFiCFmΠFiΠFm29。3cCDiCDmΠDiΠDm29。、。、。3.3100%、。。、1Jw=AσΔΠ－Δp3σStaverman。33ΔΠ。。。3.3.1McCutcheon26FO。3aCFmCFbDdCdxBCFm－CFbJwCDdCd()x=BCFm－CFb+JwC4B=0·816·22DdCd()x－JwC=05x=0C=CFbx=xC=CFmCFmCFb=expJw()k6CFmCFb=ΠFmΠFb7ΠFmΠFb=expJw()k8JwDk=DxxΠFmΠFb。ΠDmΠDb=exp－Jw()k9ΠDmΠDb。30k=ShDdh10Sh=1.85ReScdh()L0.3311Sh=0.04Re0.75Sc0.3312ShSherwoodReReynoldsScSchmidtdhLD。8、92FOJw=AΠDm－ΠFm13Jw=AΠDbexp－Jw()k－ΠFbexpJw()[]k14Tan311112。1。2SherwoodSherwood110.029dhRe。12Sherwood。1112。FOSherwood。Welty32SherwoodSh=0.332Re12ySc13Rey≤2×10515Sh=0.0292Re45ySc13Rey2×1051610、151617kc=∫L0kdy∫L0dy17kc=0.664DRet12Sc13L+0.0365DSc13ReL45－Ret45L18FO19Jw=AΠDbexp－Jwk()c－ΠFbexpJwk()[]c19kc191452L/minSherwood15Sherwood114L/min5bd。3.3.2Lee253bFO5·817·5。abSherwood1516。cdSherwood111233Fig.5ComparisonofexperimentalresultswithresultscorrectedfordilutiveECP.aandbshowexperimentalwaterfluxcorrectedfordilutiveECPusingmasstransfercoefficientdevelopedfromprimarySherwoodrelationsequation1516.canddshowexperimentalwaterfluxcorrectedfordilutiveECPusingmasstransfercoefficientobtainedfromcommonSherwoodrelationsequation111233。BCDm－CFi=DsεdCxdx－JwCx20x=0C=CFmx=τtC=CFiCFiCDm=BexpJwK－1+JwCFmCDmexpJwKBexpJwK－1+Jw21CDm－CFiCDm－CFm=11－CFmCDm1－CFmCDmexpJwKBJwexpJwK－1+1221Jw=ACDm1－CFmCDmexpJwKBJwexpJwK－1+123CFm=CFbCFmCFb=ΠFmΠFb2423K=1J()wlnB+AΠDm－JwB+AΠF()b25K=tτεDstτε、DsB·818·22ΠDmΠFb。KK。25BJw=AΠDm－ΠFbexpJwK269Jw=AΠDbexp－Jw()k－ΠFbexpJwK273cCDm=CDbK=1J()wlnB+AΠDbB+Jw+AΠF()m28B28Jw=AΠDbexp－JwK－ΠFm298Jw=AΠDbexp－JwK－ΠFbexpJw()[]k30ΠFbΠDb。2730FO34。PROFOtτε。NaCl。Cornelissen12ε、τSDKD。DsDs=ετSDKDDfree31Ds。Tan33DsDCx=E1+E2C2x+…+EnCnx32E1E2…En。PRO3b。3220BCDm－CFi=εdDCxCxdx－JwCx33x=0C=CFmx=τtC=CFiK*[=F1JwCDm－CDb+F2JwC2Dm－C2Db+…+FnJwCnDm－CnDb+GJwlnBCFi－CDm+JwCDmBCFi－CDm+JwCD()]b34FO3cK*[=F1JwCDb－CDi+F2JwC2Db－C2Di+…+FnJwCnDb－CnDi+GJwlnBCDi－CFm+JwCDbBCDi－CFm+JwCD()]i35K*=tτε。Tan。6Lee15%。Gerstandt35S=tτφtτφ、。PRO。SSPRO。5·819·633Fig.6ComparisonofthepredictedwaterfluxusingbothpreviousandmodifiedmodelforICPlayer33PRO36。Thorsen36ROCAA=3×10－12m/Pa·sB=10－7m/sTFC/HRA=5×10－12m/Pa·sB=10－8m/sTFC/ULPA=