Abstract:
Membrane gas absorption (MGA) was applied for carbon dioxide capture due to its unique potential, such as independent adjustment of gas and liquid, compact equipment installation, and sizable module. However, a major issue of MGA is membrane wetting, causing lower absorption efficiency and membrane damages. Hydrophobicity is one of the key parameters to improve membrane property for solving such problem. This thesis focused on using carbon nanotubes as the filler to composite with polyacrylonitrile (PAN) or polyvinylidene fluoride (PDVF) via a phase inversion technique to improve membranes hydrophobicity. In case of PAN, the results showed that the addition of CNT exerted insignificant effect on membrane properties and membrane hydrophobicity. Bare PAN and its composite membranes were found to get wetted after the operation for 30 min, suggesting that they would not be suitable for MGA with 3 M monoethanolamine (MEA). In case of PVDF, CNT addition affected surface porosity and also enhanced water contact angle. The best condition of CNT/PVDF composite membrane for CO2 capture was 5 % by weight of CNT in PVDF matrix, which could exert water contact angle above 97˚, uniform pore size distribution, and small pore size (254 ± 10 nm). The CNT/PVDF composite membrane could accommodate absorption flux of 7.12 mmol/m2s, namely 46 % higher than that of the bare one. Typical long-period operation (> 30 days) showed that the CNT/PVDF composite membrane slightly swelled after contacted with 3 M MEA for 30 days without surface chemical changes, resulted from chemical resistance.
