Synthesis of hydrophobic silica membranes derived from propyl trimethoxy silane and bis(triethoxysilyl)ethane for separation of volatile organic compounds from aqueous solutions

Separation and recovery of volatile organic compounds (VOCs) from aqueous solutions are important in recycling VOCs and in wastewater treatment. In recent years, pervaporation (PV) separation with a hydrophobic membrane has drawn considerable attention as an alternative to distillation for separating and recovering VOCs from aqueous solutions. In this study, a hydrophobic propyl-functionalized silica membrane, having a high affinity for ethyl acetate (EA), was prepared from propyl trimethoxy silane and bis(triethoxysilyl)ethane (BTESE) without using a molecular template. The effects of the BTESE contents in the silica precursor on the membrane properties were examined. The hydrophobic silica membrane prepared from a silica sol with a BTESE content of 7.5 mol% had an EA flux of 2.55 kg m- 2 h-1 and separation factor of 95.5 for PV of a 5 wt% EA aqueous solution at 25 degrees C. These values are the same as or greater than those of hydrophobic silica membranes prepared with cetyltrimethylammonium bromide as the molecular template, indicating our proposed method without using templates has great potential in simplifying the process for the production of hydrophobic silica membranes.