Hydrophobicity optimization of polypropylene hollow fiber membrane by sol-gel process for CO2 absorption in gas-liquid membrane contactor using response surface methodology

In membrane technology, wettability is one of the most crucial points for successful industrial application of membrane contactors. To solve this issue, a non-wetting polypropylene (PP) hollow fiber membrane was prepared by the incorporation of modified silica nano-particles (CH3SiO2) synthesized through sol-gel process on the surface and the cross-section of the membrane. Tetraethylorthosilicate (TEOS) and methyltriethoxysilane (MTES) were used as precursor and hydrophobic agent, respectively, to synthesize CH3SiO2 nanoparticles (NPs). In preparation procedure of NPs, the influential parameters including MTES/TEOS and H2O/TEOS molar ratios and NH4OH concentration were optimized using central composite design of response surface method (RSM) by considering contact angle (CA) as response variable. The CA of 168 degrees was obtained using analysis of variance (ANOVA) when the MTES/TEOS molar ratio, H2O/TEOS molar ratio and NH4OH concentration were, respectively, 3.774, 8.000 and 0.511 M. ATR-FTIR, FE-SEM, mechanical strength and porosity measurements were used to characterize the optimum membrane. The neat and modified membranes were also tested for the CO2 absorption process in a gasliquid membrane contactor system. The -CO2 absorption flux of modified membrane almost remained constant within 30 days, while the neat membrane slightly suffered from wetting problem, resulted in a continuous decline in the CO2 flux.