Development of superhydrophobic ceramic hollow fibre membranes from Malaysian kaolin for efficient carbon dioxide capture in membrane contactor

Abstract

This study initiated the development of clean technology in carbon dioxide (CO2) capture using ceramic membrane inspired by gas–liquid contacting system. The main objective in this study is to prepare inexpensive, high performance and superhydrophobic ceramic hollow fibre membranes for effective CO2 separation. Malaysian kaolin was used as the primary material for the membrane preparation. A range of additives were used in this work including alumina of different particle sizes. The hollow fibre membranes were prepared via phase inversion-based extrusion and sintering techniques, followed by grafting with fluoroalkylsilane (FAS). The effect of the addition of alumina to the pure kaolin with monosized or multisized particles on the ceramic membrane gas permeation, mechanical strength, pore size, porosity, tortuosity, morphology, and contact angle were investigated. By varying the overall loadings and particles sizes of alumina addition, different morphologies of the membrane were obtained due to alumina with multiparticle sizes exerts a thermodynamic destabilisation effect within the kaolin, accelerating the onset of demixing rate between solvent and nonsolvent, thus reducing the time during bath immersion. All fabricated kaolin-alumina membranes with multisized particles possessed higher porosity, gas permeability, mechanical strength, than the membranes prepared from pure kaolin. Finger-like structure was obtained when the suspension containing multisized particles instead of of monosized particles due to the different particles promoted the exchange between the solvent and non-solvent. In addition, the small particles moved faster to the surface during phase inversion process than those of large, resulting, multisized particle in shorter inversion time, hence, fast precipitation. The superhydrophobic membrane was obtained when kaolin with or without alumina were used as membrane materials, since kaolin surface possessed a large number of O-H groups which can easily reacting with FAS during the grafting process. The successful grafting with FAS was evidenced by the increase in contact angle from nearly equal to zero degree before grafting to 140 degrees after the grafting process. The kaolin-alumina membrane was subsequently applied in membrane contactor for CO2 absorption. The CO2 absorption flux as high as 0.18 mol m-2 s-1 was achieved at the liquid flow rate of 100 ml min-1 which was far above the fluxes of some commercial and in-house made polymeric and ceramic membranes. In conclusion, the modified kaolin-alumina hollow fibre membrane with the superhydrophobic surface, high permeability, and absorption flux is suitable for CO2 post-combustion capture, due to its outstanding chemical and thermal stabilities.