Characterization of partial pore wetting in hollow fiber gas absorption membrane contactors: an EDX analysis approach

Abstract

In this work a novel method to evaluate the partial pore wetting of gas absorption membranes is proposed. The method consists of two approaches, one by energy-dispersive X-ray spectrometry (EDX), and the other by calculating the mass transfer resistances from the gas and liquid phase in the pore, using the parameter obtained by He gas permeation experiments. For this purpose, hollow fibers were spun from polyetherimide (PEI) and polyethersulfone (PES). As well, the lumen of a PEI hollow fiber was coated with silicone rubber. The hollow fibers were then characterized by He gas permeation experiments, critical entry pressure of water (CEPw), contact angle, scanning electron microscopy (SEM) and EDX. The hollow fibers were then subjected to CO2 gas absorption using aqueous NaCl solution as absorbent. After drying the hollow fiber was subjected to the EDX analysis. The cross-sectional profile of Na and Cl content in the hollow fiber revealed that the pores of the PES hollow fibers were partially wetted, particularly at the pore inlet. Calculation of mass transfer resistances, on the other hand, revealed that the resistance came from gas phase in most hollow fibers, except for the PES hollow fiber where the liquid phase contribution was significant. Silicone rubber coating of the PEI hollow fiber increased the surface hydrophobicity and reduced the pore wetting considerably. Thus, it was concluded that the proposed method can be used as a powerful tool to investigate the pore wetting for many membrane contactor applications.