Effective oil-in-water emulsion separation by self-cleaning superoleophobic hydrogel membrane composite with hierarchical structure

Hollow fiber membranes were fabricated using polyvinylidene fluoride (PVDF) via the thermally induced phase separation method for oil-water separation. By introducing glycerol triacetate (GTA) or propylene carbonate as an extruded solvent, membrane porosity and pore size were controlled, significantly enhancing water permeance. The highest porosity and permeance were achieved with GTA as the co-extruded solvent. To further improve separation performance, a polyvinyl alcohol (PVA) coating was applied, forming a superhydrophilic and superoleophobic membrane composite. The coated membranes exhibited complete water absorption (0° contact angle) while repelling oil, preventing droplet adhesion. Antifouling performance was significantly improved, with flux recovery ratios exceeding 90% compared to 2–26% for uncoated membranes. The best-performing membrane achieved a high oil-in-water emulsion permeance of 3551 LMH/bar and 99.2% soybean oil removal efficiency. These findings demonstrate the potential of superhydrophilic and superoleophobic membranes with controlled porosity for efficient oil-water separation.