Wetting of polypropylene hollow fiber membrane contactors

Membrane wetting by absorbents leads to an increase in mass transfer resistance and a deterioration in CO2 absorption performance during the membrane gas absorption process. In order to better understand the wetting mechanism of membrane pores during their prolonged contact with adsorbents, polypropylene (PP) hollow fibers were immersed in three different absorbents for up to 90 days. Monoethanolamine, methyldiethanolamine, and deionized water were applied as absorbent solutions. The characterization results of membrane samples confirm that the absorbent molecules diffuse into PP polymers during the exposure process, resulting in the swelling of the membranes. The absorption-swelling wetting mechanism is proposed to explain observations made during the wetting process. The strong reduction of contact angles indicates that the membrane surface hydrophobicity decreases remarkably during immersion due to membrane–absorbent interaction. Membrane surface morphologies and surface roughness suffer from significant and complicated changes after immersing the membrane fibers in the absorbents. Immersion in an absorbent with a high surface tension results in small changes in membrane surface morphology. As indicated by the experimental results, improving membrane surface hydrophobicity may be an effective way of overcoming wetting problems.

Research highlights▶ The characterization results confirm that the absorbent molecules diffused into PP polymers during the exposure process, resulting in the swelling of the membranes. The absorption-swelling wetting mechanism is proposed to explain observations made during the wetting process. ▶ The strong reduction of contact angles indicates that membrane surface hydrophobicity decreased remarkably during immersion due to membrane–absorbent interaction. Membrane surface morphologies and surface roughness suffer from significant and complicated changes after immersing the membrane fibers in the absorbents. ▶ As indicated by the experimental results, improving membrane surface hydrophobicity may be an effective way of overcoming wetting problems.