Effects of sol properties and calcination on the performance of titania tubular membranes

Crack-free tubular TiO2 membranes have been successfully synthesized from colloidal titania sols by the sol-gel technique. Pore sizes of the resulting membrane were mainly controlled by the sol properties and calcination conditions. In order to obtain smaller sol particles, the pH value of titania sol should be kept higher than 2. Methylcellulose (MC) of about 0.1 wt.% in titania sol systems was suitable for use as an organic additive to improve the drying properties of titania gel. Pore sizes of the membrane prepared increased with increasing calcination temperature, especially sharply from 700 to 800°C, due to the phase transformation of titania. Pore sizes of the membrane determined by liquid/liquid displacement porometry (LLDP) were in the range of 2–20 nm in this study. Pure water permeability, molecular weight cutoff of polyethylene glycol (PEG) aqueous solution, argon permeability and the separation factor of H2/N2 mixture through the TiO2 membrane calcined at various temperatures were also measured to investigate the performance of the membrane. The comprehensive experimental data showed that the membranes prepared were crack-free and appropriate for application in liquid and gas separation.