Superhydrophilic and underwater superoleophobic PVDF-PES nanofibrous membranes for highly efficient surfactant-stabilized oil-in-water emulsions separation

Deep oil-water emulsions separation is a challenging task for oily wastewater treatment. Herein, a superwettable nanofibrous membrane was fabricated using the integrated method of electrospinning, microwave-assisted growth, and in-situ polymerization. The membrane possessed superhydrophilicity and underwater superoleophobicity due to the presence of hierarchical rough structures and hydrophilic particles and polymers. The nanofibrous membrane exhibited robust oil-water separation performances for surfactant-free oil-in-water emulsions and different types of surfactant-stabilized emulsions (e.g., SDBS, CTAB and Tween 80) solely under the effect of gravity. The membrane achieved a separation efficiency of >99.94% for surfactant-free oil-in-water emulsions with a flux of 3563.0 L m−2 h−1. The efficiency was above 98.90% with a flux of 1112.5 L m−2 h−1 for SDBS-stabilized oil-in-water emulsion solely under the effect of gravity. The membrane exhibited long-term oil-water separation efficiencies of above 97.0%. Moreover, the membrane showed remarkable stability and can maintain underwater superoleophobicity under different harsh conditions, which is key for large-scale oily wastewater treatment applications.