Effects of coagulation-bath conditions on polyphenylsulfone ultrafiltration membranes

Abstract

Polyphenylsulfone (PPSU) ultrafiltration membrane with different structures was prepared by non-solvent-induced phase separation. The effects of coagulation bath conditions (concentration and temperature) on membrane morphology, pure water flux, pore size, porosity, and contact angle were studied and discussed based on ternary-phase diagrams. Results indicated that water had stronger coagulant power than ethanol, and that the morphology of the membrane prepared from the polyphenylsulfone/1-methyl-2-pyrrolidinone/H2O (PPSU/NMP/H2O) system had finger-like structures. Conversely, sponge-like structures were observed for the PPSU/NMP/(NMP-H2O) and PPSU/NMP/(70NMP-EtOH-H2O) systems. Ethanol also greatly influenced on membrane structures. According to the Scanning electronic microscopy (SEM) image, the composition (mass fraction) of casting solution is 16% PPSU-84% NMP and the coagulation bath consisting of 70% NMP-26% H2O-4% C2H5OH. Meanwhile, the PPSU ultrafiltration membrane with spong-like was prepared under 8 ℃ coagulation bath. The formation of sponge-like structure reduces the pure water flux of ppsu membrane from 488.39 L·m−2·h−1 to 36.04 L·m−2·h−1. It also reduces the gas permeability, porosity, and pore size of the membrane. The addition of ethanol and NMP into the coagulation bath increases the roughness of the PPSU ultrafiltration membrane and reduces the hydrophilicity of the membrane.