Superhydrophobic alumina hollow ceramic membrane modified by TiO₂ nanorod array for vacuum membrane distillation

Problematic fouling along with wetting of membrane represent the main barriers for large-scale application of this technology. To solve the above problems and reinforce the anti-pollution and anti-wetting features of the distilling membrane, a brand-new TiO₂ nanorods and 1H,1H,2H,2H-perfluorodecylsilane-triethoxy (PDTS) modified alumina hollow ceramic membrane with superhydrophobic surface and self-cleaning property was prepared for utilization in the vacuum membrane distillation. To synthesize the novel membrane, a seed layer was supported on the hollow ceramic membrane by the immersion-calcination method. Then, the TiO₂ nanorods were grown on the membrane by hydrothermal method and annealed to strengthen the crystal structure. Finally, the nanorod-grown membrane was immersed in an alcohol solution of PDTS for hydrophobic treatment. The resulted modified membrane was applied to the distillation process to treat 100 g L⁻¹ of concentrated brine for 3 h. It was revealed that the modified membrane possessed with a lower ionic conductivity under 20 µs.cm⁻¹ of the permeated liquid and desirable surface superhydrophobicity at appropriate water contact angle of 152°, thus showing great promise for use in the membrane distillation process.