09-1廢水的物理化學處理法-膜

第四章廢水的物理化學處理法

第三節膜分離技術膜分離的概念：利用膜的選擇性（孔徑大小），以膜的兩側存在的能量差作為推動力，由于溶液中各組分透過膜的遷移率不同而實現分離的一種技術。膜分離技術主要包括,反滲透法ReverseOsmosis(RO)、超過濾法Ultrafiltration(UF)、微孔過濾Microfiltration(MF)、納濾Nanofiltration(NF)、電滲析法（electrodialysis

）、和隔膜電解法（diaphragmaticelectrolysis）等。它們都是通過一種特殊的半透膜來分離水中的離子和分子的技術，通稱為膜分離法1.膜分離技術概述

Membranescomparison

從如下幾個方面介紹膜技術

Bymembranematerialandporesize.Bydrivingforcesemployedandfeedflowdirection.Bymechanismsofseparation.Bytheapplicationinindustries.Bythegeometricconfiguration.ChenShuixia/ZSU1.1Membrane’sporesize

ClassificationofMF,UF,NFandROarebasedontheporesizeofmembraneemployed.ChenShuixia/ZSUSeparationSpectrum0.01NPSMICROFILTRATIONULTRAFILTRATIONREVERSEOSMOSIS0.1NPSNANOFILTRATION100MWCO10MWCO100kMWCOAlgaeCryptosporidiumBacteriaVirusGiardiaHardnessNOMSOCsSaltTurbidityOrganicMacromolecules藻類、細菌、濁度壓力驅動膜的拒斥特性一般以此膜截留物質的尺寸表示。對于脫鹽用膜如逆向滲透膜或毫微米過濾膜，可以其分子量斷點(molecularweightcutoff,MWCO)表達；對于超濾UF膜和微濾MF膜，則以其標稱孔徑尺寸(NPS)表達之。ChenShuixia/ZSU1.2Differentmaterial

Membranecanbeclassifiedbyitsmaterial:oneisorganicmaterialsuchasorganicpolymers:celluloseacetate(CA，醋酸纖維素膜),polyamide(PA，聚酰胺膜),polysulfide(PS，聚硫（砜）膜),vinylidenefluoride(VF，聚氟乙烯膜),acrylonitrile(AN，聚丙烯腈膜),etc…andanothertypeisinorganicmaterialsuchasceramicstainlesssteeletc…ChenShuixia/ZSUMembranePolymersCelluloseAcetate andDerivativesPolyamidesChenShuixia/ZSU1.3MembraneConstructionOptionsCompositeAsymmetricSymmetricChenShuixia/ZSU

1.4操作壓力

MF,UF,NFandROallbelongtopressuredrivingmembrane.Theoperationpressureisdecidedbytheresistanceofthemembranefiltrationandaswellasthecharacteristicsoftheinfluentwater.operationpressureofmembraneinorderofRO>NF>UF>MF.Topicalfiguresisgivenasfollowtable.RO-Seawater800-1000HighRO-WasteandProcess300-600HighRO-WaterPurification200-350MiddleRO-Undersink(Home)50MiddleNF100-200MiddleUF25-150MiddleMF(crossflow)10-25Low*14.5psig=1bar

Table.1:TypicalOperatingPressures-psig(bar*)MembranePressuresEnergycostChenShuixia/ZSU1.5Bymechanismsofseparation

TheseparationmechanismofMFandUFissieve,justlikeastrainer（濾網）toseparatedifferentmaterialbysize.Itisbelongtophysicalprocess.ButforNFandROaremorecomplicated.Besidethesievemechanismitalsoinvolvesmoleculemovementofdiffusionandexclusion.Itisbelongtophysicalandchemicalprocess.ChenShuixia/ZSU膜分離的物理化學原理截流機理和篩孔效應滲透和滲透壓Donnan效應機械截留（篩孔效應）物理作用或吸附截留架橋作用網絡內部截流ChenShuixia/ZSU1.6Byapplicationinindustry

RO：水的純化，改善色、味、口感等性質；也用于溶液純化如乙醇或乙二醇的提純NF：通常用于分離。如用于玉米糖漿的濃縮UF：廣泛用于不同的工業領域。在水處理中，可用于替代凝聚

coagulation,絮凝flocculation,沉淀sedimentation,過濾andmediafiltration等處理過程.也是RO和離子交換的理想的預處理步驟。

MF：可用于除去淀粉

starch,細菌bacteria,脂肪fat,霉菌molds,酵母yeastand以及乳化油emulsifiedoils.ChenShuixia/ZSU1.7Bythegeometricconfiguration（膜組件）板式Plateandframemembrane卷式Spiralwoundmodules空心纖維膜Hollowfibermembrane管式Tubularmodulemembrane

DESIGNCHARACTERISTICSpiral-WoundFibersTubularPlate&FrameCostLowLowHighHighPackingDensityHighUF-High

ROVeryHighLowModeratePressureCapabilityHighUF-Low

RO-HighUF-Low

RO-MediumHighMembranePolymer

ChoicesManyFewFewManyFoulingResistanceFairUF-Good

RO-PoorVeryGoodFairCleanabilityGoodUF-VeryGood

RO-PoorVeryGoodGoodChenShuixia/ZSU1.8summary

膜技術廣泛應用于物質分離提純、污水處理和水凈化，廢氣凈化。工業應用中的主要難題是膜的價格和堵塞。膜技術的選擇取決于被分離物質及膜的性質。例如，在水處理中，首先采用MF分離微粒，用UF消毒，然后用NFandRO除去離子。

RONFUFMF優點高效除去離子和鹽類可除去有機物、細菌、病毒，及50%to90%的鹽類地下水處理，某些組份分離。低壓。ROor