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膜领域所面临的机遇和挑战_侧重于气体分离方面_英文_

文章编号:1007-8924(2006)04-0001-05

专家论坛

Someo pportunities&challen gesforourmembrane

communitytoconsider

—withanem phasison gasse parations

WilliamJ.Koros

(GeorgiaInstituteofTechnolo

gy,SchoolofChemical&Biomolecular

Engineerin g,Atlanta,Geor gia,USA )

Ke ywords:membrane;membrane process;gasse paration;o pportunit y;challen ge

CLCnumber:TQ028.8

Documentcode:A

Ourcommunit ycommonl ycharacterizesmem 2

brane processesintermsofthesizesofthecom po 2nentsthatarebein g permeatedorre jectedb yamem 2braneincontactwithas pecificfeedstream [1].Com 2ponentsthatarere ythemembraneviasim ple hydrodynamicsievin garediverseinsizerelativeto thesus pendin gmedium,butinsuchcasesthedimen 2sionofthere jectedcom ponentist ypically greater than2nminsize,whilethesus pendin gmedium

膜领域所面临的机遇和挑战_侧重于气体分离方面_英文_

comprisesacontinuumfluidlikewater.

Fig.1 Membranes pectrumillustratin gtheboundar y betweensor ption 2diffusioncontrolandh

ydrodynamic

sievingcontrolse parationfunctionsofmembranes

Asthesizedifferencebetweenthe permeatin g componentvs.there jectedcom ponentdecreases,separationbecomesincreasin glydifficult.Indeed,neitherultrafitrationmembranemolecularwei ghtcut 2offvaluesnornominal poresizesaresufficienttocon 2trolse parationofsimilarl ysizedsolutes.Addin g knowledgeofthet ypesandamountsofchar geonso 2lutesaswellasthemor phologyandchar geonthe

membrane,however,isnowhel pin gtoachieveex 2

traordinaril yselectiveh ydrodynamic-basedse para 2

tions [2]

.

Ultimatel y,h ydrodynamicsievin gofmolecularl y dispersedsolutesoutofa “solvent ”becomesinade 2quatetoachievethedesiredfractionationwhenboth thesoluteandsolventbecomeofcom parablesize.In thiscase,sizeandsha pediscriminationbasedon

molecular jumpin gratesinvolvin gdiffusionthrou gh themembranebecomenecessar y,sointermolecular forcesarethedominantdeterminantsoftheresistance

actin goneach penetrant.Incor porationofthermod y 2namic partitionin gandmoleculardiffusion phenomena withinthemembranere quiresadditionalso phistica 2tiontodescribemicro-molecularscalese parations suchasreverseosmosis,pervaporationand gasse pa 2rations.The partitioncoefficientsenabledescribin g the processconvenientl yintermsofexternal phase conditionsandcom positions.

1 Gas&va porse parations-s pecialchallen ges Fractionain gmixturesofthesmallest penetrants inthesizes pectrumtoenable gasse paration processes requiresex quisitely precisesizeandsha pediscrimina 2tion-oftenintheran geof0.02~0.03nmbetween permeatedandre jecteds pecies.Suchdemandstrul y

作者简介:威廉?卡洛斯,男,化学工程博士,美国国家工程院院士,国际性刊物JournalofMembraneScience

主编,本刊的

国外高级顾问,美国佐治亚理工学院教授.

第26卷 第4期膜 科 学 与 技 术

Vol.26 No.4

2006年8月MEMBRANESCIENCEANDTECHNOLOGY Aug.2006