Interplay between Membrane Wetting Resistance and the Carbon Dioxide Absorption Rate in a Membrane Contactor: The Critical Role of the Gas–Liquid Interface

Abstract

Membrane wetting induced by liquid absorbents severely hinders the practical applications of a gas–liquid membrane contactor (GLMC) for carbon dioxide (CO₂) capture. To overcome this challenge, membranes with enhanced wetting resistance have been developed, but their CO₂ absorption rates have often been overlooked. Herein, we unveil the interplay between membrane wetting resistance and the CO₂ absorption rate for different GLMC membranes and elucidate the underlying mechanisms. Specifically, two representative membranes were used in this study: a polyvinylidene fluoride (PVDF) membrane with interconnected pores and an anodic aluminum oxide (AAO) membrane with disconnected pores. For each membrane, we modify it using fluoroalkyl silane agents with different chain lengths to obtain a range of membranes with different wetting resistances. Through GLMC tests, we identify a trade-off between membrane wetting resistance and the CO₂ absorption rate for the PVDF membranes, i.e., an enhanced wetting resistance leads to a lowered initial CO₂ flux. In contrast, for the AAO membranes, the CO₂ absorption rate is independent of the membrane wetting resistance. Using electrochemical impedance and ultrasonic time-domain reflectometry analysis, the interplay between membrane wetting resistance and the CO₂ absorption rate can be explained by the change of the gas–liquid interfaces in the GLMC membranes. This study reveals the critical role of the gas–liquid interface in GLMC for CO₂ capture, providing valuable insights into membrane development for environmental applications of GLMC.