Fouling-tolerant polysulfone-poly(ethylene oxide) random copolymer ultrafiltration membranes

Abstract

Asymmetric ultrafiltration (UF) membranes using polysulfone-poly(ethylene oxide) (PSF-PEO) random copolymers, synthesized by a polycondensation reaction, were prepared via a dry/wet phase inversion process. The PEO contents in copolymers varied from 0 mol% (PSF) to 20 mol% to investigate the effect of PEO on UF membrane structure, properties and performances as well as fouling tolerance. As a pore forming agent, polyvinylpyrrolidones (PVP, M-n 10k-360 kDa) with various molecular weights were used to control membrane morphologies and UF performance. Surface atomic compositions were analyzed using an X-ray photoelectron spectroscopy (XPS) to examine the enrichment of PEO segments on the membrane surface after the dry/wet phase inversion process. The pure water flux and PEG rejection (molecular weight cut off) were measured as a function of PEO contents in copolymers, PVP molecular weight, and compositions of the casting solution as well. Protein adsorption and emulsified oil filtration experiments were performed to evaluate fouling resistance for protein and emulsified oil. Compared to commercial PSF UF membranes, the surface wettability of UF membranes prepared from PSF-PEO random copolymers was significantly enhanced by the presence of hydrophilic PEO segments on the membrane surface. PSF-PEO UF membrane also showed higher pure water flux and relatively lower PEG rejection than PSF UF membrane. In the fouling experiments using BSA and emulsified oil, clearly PSF-PEO UF membranes exhibited much improved tolerance to fouling. The amount of BSA adsorption on the membrane surface was reduced significantly with increasing PEO contents and the fouling effect due to emulsified oil was lessened as well.