Study On The Performance Improvement Of Separation Membrane Using Polyaniline

Membrane separation is an advanced technology for concentration andpurification. Membrane is the key of membrane process, and the development ofmembrane with high performance has significant meaning for membrane technology.This work have investigated the enhancement of polysulfone （PSf） ultrafiltration （UF）membrane performance and polyvinylamine （PVAm） gas separation membrane usingpolyaniline （PANI）.PSf/PANI nanocomposite membranes and PSf/polyvinylpyrrolidone （PVP）membranes were prepared through immersion phase inversion using PANI nanofibersand PVP as the additives, respectively. The effects of the additives on membraneformation process, membrane structure and performance had been analyzed andcompared. When the additive contents were below0.5wt%, PSf/PANI nanocompositemembranes had higher pure water flux than PSf/PVP membranes. BSA rejection ofthe membranes was all above98%. Compared with PSf/PVP membranes, PSf/PANInanocomposite membranes had better antifouling property, mechanical strength andthermal stability.To solve the agglomeration problem of nanomaterial, PSf/PANI nanocompositemembrane was prepared using in situ blending method. During membrane formationprocess, PANI oligomers and PANI nanospheres can migrate spontaneously to themembrane/water interface. Compared with PSf membrane, nanocompositemembranes had higher surface hydrophilicity, surface pore size and porosity. Theacicular pores in the cross-section structure of nanocomposite membranes almostdisappeared and the finger-like pores became longer and better verticallyinterconnected with transfixion from membrane toplayer to sublayer. The pure waterflux of PSf/PANI nanocomposite membranes reached to1.7⁴.1times that of PSfmembrane. BSA rejection kept above96%. Moreover, PSf/PANI nanocompositemembranes had higher flux recovery ratio.PSf/PANiEB ultrafiltration membrane was prepared using PANiEB （emeraldinebase polyaniline） as the additive. PSf/PANiEB membranes exhibited much morestable pure water flux under0.30MPa TMP. After about60min of compaction,PSf/PANiEB membranes had the pure water fluxes decrement lower than30%. At 0.20MPa TMP, the pure water flux of PSf/PANiEB membrane was2.9times that ofPSf membrane. BSA rejections of the membranes were in the range of98.2%⁹8.6%.During BSA ultrafiltration, PSf/PANiEB membranes had higher flux and fluxrecovery ratio than PSf membrane. Well-dispersed PANI-PVP nanocomposite wassynthesized through dispersed polymerization and used as the additive to preparePSf/PANI-PVP nanocomposite membranes. PANI-PVP nanocomposite could stablyand long-term disperse into the casting solutions. Compared with PSf membrane,PSf/PANI-PVP nanocomposite membranes had higher surface pore size and porosity,larger macrovoids, better pore interconnection and hydrophilicity. Pure water fluxes ofnanocomposite membranes were1.8³.5times that of PSf membrane. BSA rejectionsof all the membranes kept above97%. After BSA ultrafiltration for90min, fluxretentions of nanocomposite membranes were71%⁸0%, which was higher than thatof PSf membrane.PVAm-PANI/PSf gas separation membranes were prepared using PANI as theadditive. In the tests with CO₂/N₂mixed gas （containing15vol%CO₂and85vol%N₂）, the proper addition of PANI could simultaneously enhance CO₂permeance andCO₂/N₂selectivity of membranes. The effects of mPANI/mPVAm（mass ratio of PANI toPVAm） in the casting solution and wet coating thickness on membrane performancehad been investigated and the optimal parameters for membrane preparation had beenobtained. PVAm-PANI/PSf membrane prepared with wet coating thickness of50μmand mPANI/mP VAm in the casting solution of0.2had CO₂permeance of2034,951and161GPU and CO₂/N₂selectivity of159,102and49at0.15,0.5and1.5MPa feedpressure, respectively.