Preparation Of Antifouling, High Flux Porous Membranes And Membrane Process Intensification

Membrane fouling and low permeation flux constitute the bottleneck limiting thewide application of polymeric membranes. Preparation of antifouling and high fluxmembranes has become one of the most important research issues in membraneseparation area. The target of the thesis is to prepare antifouling asymmetric,composite and free-standing membranes. We design the membrane matrix material(amphiphilic brush-like polymer), optimize the membrane formation conditions(adjusting coagulation temperature, generating covalent bonds between active layerand support), invent a new fabrication approach of free-standing membrane(space-confined polymerization) and achieve the preparation and processintensification of the antifouling, high flux membranes.Starting from the mechanism of nonsolvent induced phase inversion and moleculardesign protocol, we investigate the surface segregation behavior of hydrophilicpore-forming agent polyethylene glycol (PEG) and amphiphilic Pluronic F127undervarious coagulation bath temperatures. The influence of coagulation bath temperatureon the cross sectional morphology, pore size, surface hydrophilicity, separation andantifouling properties of the poly(ethylene sulfone)(PES) asymmetric membranes issystematically studied. We design and synthesize the brush-like amphiphiliccopolymer PES-g-poly(ethylene oxide) dimethacrylate (PEGMA) with the PES asmain chain and the polyPEGMA as side chains. The asymmetric PES-g-PEGMAmembranes are prepared using PES-g-PEGMA as the membrane matrix material. Theimpacts of graft yield of PEGMA and the length of PEG segment on themembrane-formation properties, surface composition, surface hydrophilicity andprotein adsorption are investigated. The PES-g-PEGMA membranes maintain theexcellent membrane-formation property of the PES membranes. Compared to the PEScontrol membrane, the PES-g-PEGMA membranes are endowed with surfacehydrophilicity and lower protein adsorption. Beside, the separation properties andantifouling properties of the PES-g-PEGMA membrane were enhanced.Based on the mechanism of interfacial polymerization, the carboxyl groups onthe hydrolyzed polyacrylonitrile (HPAN) membrane surface are activated byN-(3-Dimethylaminopropyl)-N’-ethylcarbodiimide hydrochloride (EDC)/N-Hydroxysuccinimide (NHS), the interfacial polymerization between piperazidine(PIP) and trimesoyl chloride (TMC) is mediated by the generating amide bonds between the active layer and the support. The morphology and zeta potential of activelayer is optimized. The flux of the PA-EDC-HPAN composite membrane is of a highlevel. The PA-EDC-HPAN composite membrane is endowed with anti-protein-foulingproperties via blending hydrophilic polyvinyl alcohol (PVA) with PIP.We invent a space-confined approach to the poly(2-hydroxyethyl methacrylate)(polyHEMA) free-standing membranes. The influence of membrane formationthermodynamics and dynamics on membrane morphologies and surface properties isstudied. The impacts of pore-forming agent on the membrane pore size and porosity isinvestigated. The polyHEMA free-standing membrane thickness can be easilyadjusted. The polyHEMA membranes possessed the superhydrophilicity, high fluxand strong antifouling properties. Through blending the fluorine-containing monomerdodecafluoroheptyl methacrylate (DFHM) with the hydrophilic monomer HEMA, themembrane with amphiphilic surface bearing hydrophilic domains and low surfaceenergy domains is constructed. The membranes show high flux and strong antifoulingproperties. Through blending with the weak acid monomer methylacrylic acid (MAA)or the temperature-sensitive monomer N-isopropylacrylamide (NIPAAm), thefree-standing membranes with antifouling, pH/temperature stimuli responsiveproperties are prepared.