Double-Defense Design of Super-Anti-Fouling Membranes for Oil/Water Emulsion Separation

Oil fouling threatens the water flux stability of membranes for oil/water separation. Simple hydrophilic modification fights for an opportunity to prevent oil contamination but fails to eliminate severe water flux decline. In essence, a “single-defense” mechanism is insufficient to build a potent barrier against accumulated cake layer under a filtration environment. This work reports a “double-defense” design by integrating hydrophilic polymer brushes and hydrogel layer on oil/water separation membranes for desired anti-oil-fouling property, where a poly(vinylidene fluoride) porous membrane is first covered by a layer of poly(hydroxyethyl methylacrylate) hydrogel and then controllably grafted with poly(sulfobetaine) brushes. The spatially hierarchical structure establishes a highly covered “double-defense” barrier for the membrane surface to efficiently repel oil adhesion and the formation of an accumulated cake layer. When separating various surfactant-stabilized oil-in-water emulsions, the permeating flux displays a nearly zero decline throughout the whole filtration period. Most importantly, the permeating flux of the membrane is almost the same when filtrating pure water and filtrating oil-in-water emulsions, which is difficult to be achieved by the general membranes, indicating that the membrane has excellent anti-oil-fouling property superior to the currently reported membranes.