In situ biomineralization-constructed superhydrophilic and underwater superoleophobic PVDF-TiO2 membranes for superior antifouling separation of oil-in-water emulsions

In situ construction has emerged for fabricating superwetting PVDF membranes with uniform organic coatings and improved resistance to oil fouling, but it remains almost unexplored to apply this strategy to attain durable inorganic coatings and prepare superior antifouling PVDF membranes. Herein, we developed a novel in situ biomineralization method to fabricate superhydrophilic and underwater superoleophobic PVDF-TiO2 membranes with conformal TiO2 coatings on both the top and internal surfaces. An initial flux of 400 L m−2 h−1 (LMH) with a final flux of 200 LMH at 2.5 h under 0.1 bar, oil rejection higher than 99.7%, and highly stable cycling performance (5 cycles at 130 min each) were achieved on crossflow filtration of surfactant-stabilized oil-in-water emulsions. We used a new “flux map” to make a relatively fair comparison among the reported membranes, which suggested the superior performance of our PVDF-TiO2 membrane. The demonstrated exceptional performance was attributed to the low oil adhesion and great hydrophilicity enabled by the durable and superwetting coatings composed of densely packed TiO2 nanoparticles on the entire membrane, as well as to the relatively smooth top surface with an appropriate surface pore size that alleviate the oils being trapped by the surface structures.