ZrO2 and TiO2 membranes for nanofiltration and pervaporation: Part 2. Development of ZrO2 and TiO2 toplayers for pervaporation

This paper reports the preparation of novel ZrO2 and TiO2 membrane layers with a tight pore structure for pervaporation applications, a high thermal and a high chemical stability. Optimized α-Al2O3/γ-Al2O3/ZrO2 and α-Al2O3/γ-Al2O3/TiO2 multilayer membranes, having a toplayer with a thickness 50–100 nm, were found defect-free in permporometry and displayed a high selectivity in standard pervaporation tests with alcohol/water mixtures. Separation tests at 70 °C demonstrated a separation factor exceeding 300 for a 95/5-wt% IPA/water mixture for both membranes. For the membrane with ZrO2 toplayer, the membrane quality was further demonstrated by applying ethanol/water as a feed mixture (separation factor > 150).