Superhydrophobic Sponge for Highly Efficient Separation of Both Stratified and Emulsified Oil-Water Mixtures

Efficient separation of oil-water mixtures, particularlyhomogeneous and stable emulsions, has always been an industrial challenge.Herein, we report a facile, cost-effective procedure for fabricatingsuperhydrophobic melamine sponges using a single solution-immersionprocess. The modified sponge has stable superhydrophobicity owingto the synergy of triple hydrophobic mechanisms with a maximum watercontact angle of 158 degrees. As an absorbent, the modified sponge blockexhibits high porosity, outstanding absorption capacity, excellentmechanical properties, and superior physical and chemical stability,enabling its use for the separation of stratified oil-watermixtures via repeated absorption-extrusion processes with aseparation efficiency of nearly 100%. Furthermore, as a filter, thecrushed, modified sponge powders exhibit a demulsification efficiencyranging from 97.65 to 99.33% for the separation of ideal water-in-oilemulsions under gravity. Finally, the feasibility of these spongesfor oilfield applications is established through the demonstrationof the continuous separation of an emulsion of brine in crude oilusing the modified sponge powders in conjunction with an in-housebuilt apparatus. This work may open a viable pathway for the efficientseparation of both stratified and emulsified oil-water mixturesvia wettability, and provide a novel strategy for the reuse of wastesponges.