Enhancement of water permeability in SiO2-ZrO2 nanofiltration membranes via adding organic solutes into the SiO2-ZrO2 sols

SiO2-ZrO2 nanofiltration membranes were prepared by adding glucose into SiO2-ZrO2 sols, followed by coating on cylindrical alumina porous support and firing at 550 °C. The average pore sizes of the SiO2-ZrO2 membranes by adding glucose in the SiO2-ZrO2 sols were larger than without adding glucose in sols. Water permeabilities of SiO2-ZrO2 membranes, prepared from 1.0 wt% SiO2-ZrO2 sols with and without the addition of 0.5 wt% glucose, were 4.2 × 10−12 m3/ (m2 s Pa) and 2.0 × 10−12 m3/ (m2 s Pa), respectively, while both of SiO2-ZrO2 membranes with and without addition of glucose showed approximately the same molecular weight cut-off (MWCO) of 300 g/mol. After membrane treatment in water at 90 °C, the water permeability of 1 wt% SiO2-ZrO2 membranes increased dramatically, while the MWCO of membranes remained the same as that before the treatment. The water permeability of membranes with and without addition of 0.5 wt% glucose increased from 4.2 × 10−12 to 9.1 × 10−12 m3/ (m2 s Pa) for MWCO of 320 g/mol and from 2.0 × 10−12 to 4.9 × 10−12 m3/ (m2 s Pa) for MWCO of 300 g/mol, respectively. An increase in the water permeability of SiO2-ZrO2 membranes after treatment in water at 90 °C can be explained by increasing in the hydrophilic surface and inner membrane pore and the dissolution of silica into hot water. SiO2-ZrO2 membranes with doping glucose achieved enhancement in the water permeability and hydrothermal stability.