Fabrication of high performance ZrO₂-TiO₂ NF membranes via a modified colloidal sol-gel process

The optimized ZrO₂-TiO₂ composite colloidal sols with an average particle size of 3 nm were successfully synthesized via a modified colloidal sol-gel process by using water as solvent. Tubular α-Al₂O₃ membranes with a mean pore size of 5 nm were used as the intermediate layers. Defect-free ZrO₂-TiO₂ NF membranes were then fabricated on the interlayer surface via a dip-coating method. The ZrO₂-TiO₂ NF membranes with an average toplayer thickness of 200 nm showed the relatively high pure water permeability of about 23 L·m^-2·h^-1·(0.1 MPa)^-1 and low MWCO of about 600. Meanwhile, the ZrO₂-TiO₂ NF membranes indicated the high retention rates for Co²⁺, Sr²⁺ and Cs⁺ of 99.6%, 99.2% and 75.5% at the condition of low salts concentration, pH=3 and the transmembrane pressure of 0.9 MPa, respectively.