Preparation of Micro-porous Polyethersulphone Hollow Fibre Membranes Using Non-solvent Vapour-induced Phase Separation

Using a dope comprised of polyethersulphone (PES):N,N-dimethylacetamide:diethylene glycol (DEG) 17:43:40 (wt%), micro-porous PES hollow fibre membraneswere prepared by non-solvent vapour-induced phase separation (VIPS).The effects of bore fluid solution composition, coagulation bath temperature, air-gapdistance and humidity on the morphologies of micro-porous PES hollow fibremembranes were investigated. Light transmission microscopy was used to determinethe precipitation rate during VIPS stage as well as during non-solvent liquid-inducedphase separation (LIPS) stage. The mean pore radius of PES hollow fibre UFmembranes with sponge-like structures could be calculated by Image software fromthe SEM images. The mean pore radius of outer surface was about 0.1 μm (0.092 ~0.131 μm, PES3 ~ PES14) while the mean pore radius of the inner surface of PEShollow fibre membranes was 0.051-0.064 μm (PES12 and PES14). Pure waterpermeation fluxes and rejections were closely related to both the inner and outer skinlayers. When inner and outer surfaces possessed open structure, the pure waterpermeation fluxes increased, whereas rejections decreased accordingly. PES hollowfibre membranes with pure water permeation flux from 387 to 1210 L.m^-2.h^-1.bar^-1 aswell as rejection of 10.1%-98.1% could be achieved by adjusting air humidity,air-gap distance and composition of bore fluid solution. Pure water permeationfluxes of PES12, PES13 and PES14 with sponge-like structures were higher than1000 L.m^-2.h^-1.bar^-1 and their BSA rejections were only about 10%.