Correlating physicochemical properties of commercial membranes with CO₂ absorption performance in gas-liquid membrane contactor

Abstract

The gas-liquid membrane contactor (GLMC) is a promising alternative gas absorption/desorption configuration for effective carbon dioxide (CO₂) capture. The physicochemical properties of membranes may synergistically affect GLMC performances, especially during the long-term operations. In this work, commercial polypropylene (PP) and polyvinylidene fluoride (PVDF) hollow fiber (HF) membranes were applied to explore the effects of their physicochemical properties on long-term CO₂ absorption performances in a bench-scale GLMC rig. PP membranes with pore size of 19 nm, thickness of 0.046 mm, and porosity of 58% achieved high CO₂ flux when feeding pure CO₂ (5.4 and 24.4×10 mol/m .s using absorbents of water and 1M monoethanolamine (MEA), respectively) whereas PVDF membranes with pore size of 24 nm, thickness of 0.343 mm, and porosity of 84% presented a good CO₂ separation performance from the simulated biogas using 1M MEA (6.8×10 mol/m .s and 99.9% CH recovery). When using water as absorbent, the coupled phenomena of membrane wetting and fouling restricted CO₂ transport and resulted in continuous flux loss during the long-term operations. When using MEA as absorbent, both PP and PVDF membranes suffered dramatic flux decline. A series of membrane characterization tests revealed that the morphology, pore size, hydrophobicity, and stability of selected commercial membranes were greatly affected by MEA attack during long-term operations. Therefore, the selection criterion of microporous membranes for high-efficiency and long-term stable CO₂ absorption in GLMC processes was proposed. It is envisioned that this study can shed light on improving existing membrane fabrication procedures and the application of novel membrane surface modification techniques to facilitate practical applications of the GLMC technology.