Superhydrophobic Modification of the PVDF Membrane by Fluorinated TiO₂ Nanoparticles To Improve Membrane Distillation Performance

Membrane distillation (MD) is a thermal-based membrane separation process driven by vapor pressure differences generated by temperature differences, and has great potential for applications in desalination, wastewater treatment, and resource recovery. However, during long-term operation, wetting and fouling lead to deteriorated permeate quality and treatment efficiency. Herein, we developed a surface modification method for the polyvinylidene difluoride (PVDF) membrane to improve the antifouling and antiwetting ability without sacrificing permeability. This method imparts superhydrophobic properties to the PVDF membrane by depositing fluorinated TiO2 nanoparticles (NPs) on its surface. The modified PVDF membrane exhibited a higher water contact angle (WCA, 157.4°) and an ultralow water sliding angle (WSA, 2.1°), indicating successful superhydrophobic modification. The modified PVDF membrane possessed superior resistance against fouling and wetting. In 150-h operation of direct contact membrane distillation, it exhibited robust performance in treating a hypersaline solution (100 g/L NaCl) containing foulants (50 mg/L humic acid). The results also verified that the TiO2 layer was firmly attached to the membrane surface. Our study demonstrates that this surface modification approach can effectively improve the membrane performance of the MD process for treatment of high-salinity solution containing foulants.