Superhydrophobic ceramic hollow fibre membranes for trapping carbon dioxide from natural gas via the membrane contactor system

Abstract

The membrane contactor system is one of the most important technologies to trap CO2 from natural gas. To apply this technology, hollow fibre membranes with a superhydrophobic surface must be used, where membranes were prepared from kaolin clay through the phase inversion/sintering technique and modified by three types of fluoroalkylsilane (FAS) molecules (C6, C8, C10) at different immersion times (6, 24, 48,72 h) to capture CO2 from natural gas via contacting the gas-liquid system. The kaolin was chosen due to its abundant availability at an affordable price as well as the high amount of the hydroxyl (OH) group in the surface which easily reacts with FAS during the grafting process. Superhydrophobicity was distinguished by Fourier transform infrared (FTIR), scanning electron microscopy (SEM), liquid entry pressure of water (LEPw) measurement, and contact angle (CA). The lowest pore size of the grafted membrane obtained for C8 was about 1.32 μm; it was considered the perfect target for high membrane resistance. The chosen superhydrophobic kaolin membrane was tested for carbon dioxide (CO2) capture via the membrane contactor system. With increasing time of immersion, the hydrophobicity phenomena rose gradually until superhydrophobicity property was obtained. Forty-eight hours was proven as sufficient time to obtain the desired superhydrophobicity property to avoid wetting pores of the membranes. Besides, the perfect type of FAS for separating CO2 was C8 based on the sufficient LEPw and contact angle. The reduction of pH was observed after testing the performance of using a membrane contactor to separate CO2 by using water as absorbent where pH value decreased from 6.6 to 4.3 within 1 h, which concludes the success of the gas-liquid system into removing CO2 from natural gas.