Fabrication of membranes for the liquid separation: Part 2: Microfiltration membranes prepared from immiscible blends containing polysulfone and poly(1-vinylpyrrolidone-co-acrylonitrile) copolymers

In the previous research, ultrafiltration membranes exhibiting excellent performance were produced from the miscible blends of polysulfone (PSf) and poly(1-vinylpyrrolidone-co-acrylonitrile) (P(VP-AN)) copolymers. PSf formed miscible blend with P(VP-AN) copolymers containing AN from 2 to 16 wt%, while other P(VP-AN) copolymers were not miscible with PSf. In this study, microfiltration membranes are prepared from immiscible blends of PSf and P(VP-AN) copolymers via traditional phase inversion process. Even though compatibility of PSf/P(VP-AN) blends depends on the AN content of copolymer, the average pore size existing on the membrane surface was about 0.25 μm regardless of copolymer composition. These micropores stemmed from solvent–nonsolvent exchange channel formed at around the interface between PSf and P(VP-AN) when blends contain less than about 30 wt% of copolymer. Macropores (2 μm) originated from the dispersed particles (or copolymer rich phase) was observed on the membrane surface along with micropores when the blend contained more than 40 wt% copolymers.