Impact of dope extrusion rate and multilayer polydimethylsiloxane coating on asymmetric polyethersulfone hollow fiber membrane for CO2/N2 and CO2/CH4 separation

Abstract

AbstractCarbon dioxide (CO2) emissions to the atmosphere have greatly contributed to climate change as the concentration has increased since the pre‐industrial period. Various mitigation strategies have been developed to combat climate change with membrane being one of the growing alternatives. Pristine hollow fiber (HF) membrane typically exhibits lower selectivity as compared to dense flat sheet membrane. In this study, we developed an asymmetric HF polyethersulfone (PES) membrane with critical concentration at two different dope extrusion rate (DER) at 3 and 6 mL/min to be studied for CO2/N2 and CO2/CH4 gas separation for flue gas and biogas upgrading applications by testing the fabricated membrane with pure gas permeation test with variable pressure at room temperature. It was observed that HF membrane extruded with high DER exhibits finger‐like structure beneath the skin layer with more pinholes compared to HF extruded with low DER. The gas permeance was observed to increase in linear fashion as function of upstream pressure while the gas selectivity appears to be relatively constant regardless of upstream pressure. Meanwhile, polydimethylsiloxane (PDMS) coated HF PES membrane shows lower gas permeance as compared to its pristine membrane with improved CO2/N2 and CO2/CH4 selectivity. HF PES membrane extruded at 3 mL/min shows relatively low gas permeance, CO2/N2 and CO2/CH4 selectivity as compared to HF PES extruded at 6 mL/min. Additionally, this study shows that sequential coating of PDMS layer does not improve gas selectivity performance of the fabricated asymmetric PES HF membrane while the gas permeance reduction was observed.