Environment-benign preparation of Ag toughening TiO₂/Ti tight ultrafiltration membrane via aqueous sol–gel route

A new aqueous sol was synthesized to prepare Ag-doped TiO₂/Ti composite tight ultrafiltration (UF) membranes. This sol was prepared based on water (>95 wt%), for which the hydrodynamic size of 8 nm could be obtained by tuning the electrostatic and steric repulsive forces, breaking the limit of the polymeric sol–gel method to prepare tight UF membranes. For the preparation of the sol, high water content can significantly reduce the use of organic solvents and is more environment-benign. Moreover, Ag doping can considerably improve the toughness of the supported membranes to efficiently prevent the TiO₂/Ti composite membranes from cracking and overcome the thermal expansion mismatch of ceramic membranes and their metallic supports. The prepared Ag-doped TiO₂/Ti composite membranes presented a molecular weight cut-off of 3 kDa with a pure water flux of 24 L m⁻² h⁻¹ bar⁻¹ and exhibited good dye removal capabilities. The proposed Ag doping method has considerable potential for the fabrication of integrated hybrid ceramic–metallic composite membranes.