Cellulose Sponge with Superhydrophilicity and High Oleophobicity Both in Air and under Water for Efficient Oil–Water Emulsion Separation

Oil–water emulsions stabilized by surfactants are fine dispersions of oil in water or of water in oil and difficult to separate which will lead to serious water pollution. A more recent development is the ability to fabricate oleophobic–hydrophilic surfaces in air, which are not easy to construct due to the difference surface tension between water and oil. Herein, a cellulose sponge with multipore structure is fabricated to increase the removal efficiency. Amphiphilic molecular brushes of polyethylene glycol with short perfluorinated end caps (F-PEG) are grafted on cellulose sponges to solve the contradictory relation of hydrophilicity and oleophobicity and improve oil/water selective wettability and fouling resistance. Besides, stable superhydrophilicity and superoleophobicity under water, corrosive liquids, and high oleophobicity in air conditions are exhibited in the F-PEG grafted porous cellulose sponges with textured surfaces (F-g-CS). And the separation efficiency and rate of F-g-CS with surface of nanopores are 99.92% and 180 L m⁻² h⁻¹, while that of micropores are 99.83% and 297 L m⁻² h⁻¹ only under gravity. It is demonstrated that the grafting F-PEG molecules imparted F-g-CS of micropores surface with high flux and separation efficiency simultaneously. Furthermore, antifouling property and collection of water in oil–water mixture without fouling are possessed in F-g-CS. (Figure presented.).