Mesoporous TiO2 based membranes for water desalination and brine processing

This work shows the preparation, characterisation and testing of TiO2 membranes dip-coated on commercial α-Al2O3 tubes for desalination. TiO2 thin films (∼400 nm) were synthesised from titanium propoxide and exposed to a gentle thermal treatment to control particle and pore sizes (dp ∼ 4 nm). The TiO2 membranes were tested for brackish (0.3 wt%), sea water (3.5 wt%) and brine concentrations (7.5 and 10 wt%) up to 75 °C in a pervaporation setup. Water fluxes as high as 10.5 kg m−2 h−1 were achieved for brackish concentrations, whilst values of up to 4.0 and 6.0 kg m−2 h−1 were measured for the highest brine concentration (10 wt%). Concentration and temperature polarisation both affected the water fluxes, particularly for brine solutions, though the latter was more dominant. Salt rejection remained very high at ∼99% for all tested conditions, thus demonstrating the feasibility of mesoporous inorganic TiO2 structures for desalination and brine processing. The TiO2 membranes proved to be stable for long term (>350 h) testing even under thermal cycling conditions.