Salt-induced fabrication of superhydrophilic and underwater superoleophobic PAA-g-PVDF membranes for effective separation of oil-in-water emulsions

Conventional polymer membranes suffer from low flux and serious fouling when used for treating emulsified oil/water mixtures. Reported herein is the fabrication of a novel superhydrophilic and underwater superoleophobic poly(acrylic acid)-grafted PVDF filtration membrane using a salt-induced phase-inversion approach. A hierarchical micro/nanoscale structure is constructed on the membrane surface and endows it with a superhydrophilic/ underwater superoleophobic property. The membrane separates both surfactant-free and surfactant-stabilized oil-in-water emulsions under either a small applied pressure (<0.3 bar) or gravity, with high separation efficiency and high flux, which is one to two orders of magnitude higher than those of commercial filtration membranes having a similar permeation property. The membrane exhibits an excellent antifouling property and is easily recycled for long-term use. The outstanding performance of the membrane and the efficient, energy and cost-effective preparation process highlight its potential for practical applications. Salting away: The title membranes having different PAA graft ratios were fabricated by using a salt-induced phase-inversion process. The membrane can separate both surfactant-free and surfactant-stabilized oil-in-water emulsions under either a small applied pressure (0.1 bar) or gravity, with a high separation efficiency and high flux. CA=contact angle.