Pervaporation of organic/water mixtures with hydrophobic silica membranes functionalized by phenyl groups

Hydrophobic silica membrane was prepared on a porous alumina support with γ-alumina interlayer by a sol–gel method using tetraethoxysilane (TEOS) and phenyltriethoxysilane (PhTES). Cetyltrimethylammonium bromide (CTAB) was used to control the pore size by acting as a molecular template, and to improve the flux through the membrane. The effects of CTAB concentration and PhTES content in silica source on the membrane performance for pervaporation of EA/water were investigated. The phenyl-functionalized silica membranes were characterized by Fourier-transform infrared spectroscopy, field emission scanning electron microscopy, contact angle measurement and single gas permeation measurement. The membranes were used for recovery of organic compounds by pervaporation separation of ethyl acetate (EA), methylethyl ketone (MEK) and isopropanol (IPA) in aqueous solutions. The permeation flux and separation factor of EA (5 wt%)/water at 313 K using the hydrophobic silica membrane were 1.94 kg m−2 h−1 and 216, respectively. The separation factor for pervaporation of EA/water was larger than that for vapor liquid equilibrium. The fluxes and separation factor of organic components had values in the order EA > MEK > IPA. We suggest that this result is based on the order of hydrophobicity of the organic compounds and kinetic diameter.