The effect of air gap on the morphological properties of PSf/PVP90 membrane for hemodialysis application

Abstract

Membrane morphology plays an important role in achieving high flux and excellent uremic toxin removal for efficient hemodialysis therapy. Hemodialysis membrane morphology correlates to spinning parameters applied during fabrication of membrane. The effect of air gap on the morphology and liquid separation performance of the polysulfone (PSf) hemodialysis membrane is investigated. PSf hollow fibre membranes were prepared via dry-wet spinning process from dope solution comprises of 18 wt% PSf and 4.8 wt% polyvinylpyrrolidone in Nmethyl- 2-pyrrolidone. The membrane morphology was characterised using a scanning electron microscope (SEM) before tested with the ultrafiltration system to measure the pure water flux (PWF) and protein rejection using bovine serum albumin (BSA). SEM analysis revealed that the air gap does change the structure of the membranes due to the elongation stress because of the gravitational pull on the PSf hollow fibres. At low air gap (3 cm), the lower average pore size on the outer surface reduced the PWF while at high air gap (50 cm), the larger average pore size of membranes permitted water molecules to pass through easier and faster. It was observed that the PWF of the membrane increased significantly with air gap due to the increasing pore size. Membrane fabricated at 50 cm air gap obtained better PWF (28.45 Lm-2h-1) and protein rejection (94.47 %) compared to the membranes fabricated at 3 and 30 cm air gap. The effect of air gap enhanced the morphology and the performance of PSf membrane for hemodialysis application.