Effect of coagulation bath conditions on the morphology and performance of PSf membrane blended with a capsaicin-mimic copolymer

Abstract

In this study, asymmetric polysulfone (PSf) membranes with capsaicin-mimic groups were prepared from PSf/P(H-M)/DMAc system via phase inversion induced by immersion precipitation. Effects of coagulation bath temperature and composition on morphology, wettability, pure water permeability (Lp), separation performance and anti-fouling property of the prepared membranes were systematically studied by scanning electron microscopy, contact angle measurement and fouling–filtration experiments. The results demonstrated that the elevation in the coagulation bath temperature resulted in greater formation of macrovoids and lower surface hydrophilicity, which attributed to higher both pure water permeability and permeation flux for filtration of HA solution, yet lower both HA rejection and anti-fouling capacity. Either ethanol or glacial acetic acid with different concentrations was used as non-solvent coagulation bath in this study. It was shown that pores on the membrane surface changed larger in size and then obviously shrank with an increase in either ethanol or GAA concentration in the testing range, while the surface hydrophilicity of the membranes was gradually enhanced. When 25% ethanol solution was used in coagulation bath, the membranes exhibited the excellent permeability, separation performance as well as anti-fouling capacity. Moreover, ethanol has several advantages over GAA on the fabrication of the membranes with higher hydrophilicity, permeability, permeation flux and anti-fouling capacity, while GAA favors the improvement in HA rejection of the membranes. On the whole, adjusting coagulation bath condition is an effective approach to tailor the separation performance and anti-fouling capacity of the formed P(H-M)-containing PSf membranes.