Preparation, characterization, and evaluation of TiO2-ZrO2 nanofiltration membranes fired at different temperatures

TiO2-ZrO2 nanofiltration membranes were successfully prepared using a sol-gel method. Two types of TiO2-ZrO2 sols (polymeric and colloidal sols) with molar ratios of 5/5 were coated onto α-Al2O3 cylindrical porous supports followed by firing at different temperatures. The structures of the membranes were amorphous up to a firing temperature of 500 °C. Measurements of the N2 permeance and water permeability revealed that values for average pore size, N2 permeance, and water permeability (Lp) of the prepared membranes were increased with increases in the firing temperature, and a drastic increase was observed at the temperature of transformation from an amorphous to a crystalline phase. For the membranes fired at 200-600 °C, the average pore size and N2 permeance was 0.5-0.8 nm and 0.14-0.54 × 10−5 mol/(m2 s Pa), respectively; nanofiltration performance showed molecular weight cut-offs (MWCOs) of 200-810 g/mol, and Lp of 2-12 × 10-12 m3/(m2 s Pa), respectively. In the present study, values for the structure and separation performance of the membranes were successfully controlled via the use of different sizes of sols and by manipulating the firing temperature.