Investigation of membrane wetting in different absorbents at elevated temperature for carbon dioxide capture

Abstract

In order to investigate the mechanism of membrane wetting in the membrane absorption process at elevated temperature, the commercial polypropylene (PP) hollow fiber membrane was used to simulate the absorption exposure conditions by immersing the membrane into different absorbents at 60°C up to 40 days. Three absorbents which are 30wt% of aqueous monoethanolamine (MEA), 2-amino-2-hydroxymethyl-1,3-propanediol (THAM) and potassium sarcosinate (KSar) were selected to investigate the interaction between absorbents and membrane. Several characterization methods including X ray photoelectron spectroscopy (XPS), field emission scanning electron microscope (FE-SEM), atomic force microscope (AFM), mercury intrusion porosimetry (MIP) and contact angle measurement were used to study the changes of membrane properties. The results showed that the pore size, porosity and surface roughness of membrane increased after immersion. XPS demonstrated that absorbent molecules diffuse into the polymer matrix resulting in the swelling of membrane. Membrane deformation is dependent on the surface tension of the absorbent. KSar with a high surface tension caused less deformation of membrane than other absorbents.The change of membrane resistances as a function of operating time was also examined by continuous testing of membrane modules for a prolonged period under membrane absorption conditions at 60°C. It is found that transmembrane pressure has significantly increased the membrane resistance. KSar has a less tendency of increasing membrane resistance than MEA and THAM, but this advantage is not as significant as that at lower temperature.