(605g) Liquid and Super Critical CO2 Transport through Surface Modified Hydrophobic Mesoporous Ceramic Membranes

The permeability of liquid and super critical CO₂, and some selected organic solvents were examined in unmodified and surface-modified 5 and 10 nm titania, 5 nm ã-alumina ceramic membranes. The unmodified ceramic membranes are hydrophilic in nature. By surface modification, these membranes were made hydrophobic. The hydrophilic behavior of the oxide materials of the ceramic membranes leads to adsorption of liquid into different layers of membrane. When the pore diameters of the layers become smaller, the pressure required to bring the liquid back out of the membrane becomes too high and systems cannot support such pressures. The ceramic membranes were modified by formation of a hydrophobic layer of organosilane compound on the membrane surface. Two different fluorinated silanes (octyltrichlorosilane and 1H,1H,2H,2H-perfluorodecyltriethoxysilane) were used for membrane surface modification. Octyltrichlorosilane grafting was carried out in ethyl acetate, while 1H,1H,2H,2H-perfluorodecyltriethoxysilane grafting was done in chloroform under argon environment to avoid self-polycondensation of the silanes. The modified and unmodified membranes surface chemistry was assessed using contact angle measurements with water, scanning electron microscopy (SEM), energy dispersive X-ray analysis (EDS), and infrared absorption. The permeability of liquid and supercritical CO₂ and some selected solvents varied significantly in modified and unmodified membranes. In this paper we will present some experimental solvent permeability data and provide a theoretical basis to explain the solvent transport characteristics through modified and unmodified mesoporous ceramic membranes.