Dehydrofluorination and One-Pot Hydrothermal Process for Polyvinylidene fluoride/Polytetrafluoroethylene@TiO2 Membranes with Durable Superhydrophobicity toward Repeatable Separating and Photodegrading Oily Dyes in Water-in-Oil Emulsions

The photocatalytic and inherently hydrophilic characteristic of titanium dioxide (TiO 2 ) make it very suitable for separating oil-in-water emulsion and aqueous pollutants removal. However, the removal of the oily dyes in water-in-oil emulsion usually needs superhydrophobic/superoleophilic membranes. Although surface modification of TiO 2 with fluorinated organic compounds can bring hydrophobicity, the hydrophobic surface would change back to a hydrophilic surface again after light illumination as fluorinated organic molecules are easily photodegraded too. To date, very few reports have successfully fabricated TiO 2 photocatalysts keeping long-term superhydrophobicity after repeatable photodegradation. Herein, an approach to fabricate polyvinylidene fluoride (PVDF)/polytetrafluoroethylene (PTFE) @TiO 2 nanofibrous membranes through dehydrofluorination and one-pot hydrothermal process, which possess stable superhydrophobicity in various harsh environments, is reported. For the first time, PTFE is bonded with PVDF through dehydrofluorination which induces crosslinking between PTFE and PVDF chains. Owing to the existence of PTFE, extensive hydrophobic TiO 2 can be in situ grown on the rough surface of PVDF/PTFE nanofibers through one-pot hydrothermal process. These features ensure that the membranes possess durable and high-efficient water-in-oil emulsion separation and photodegradation performance. The photodegradation efficiency of the PVDF/PTFE@TiO 2 membranes for oil-soluble dyes remains above 95% even after ten cycles.