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

Efficient separation of oil–water mixtures, particularly homogeneous and stable emulsions, has always been an industrial challenge. Herein, we report a facile, cost-effective procedure for fabricating superhydrophobic melamine sponges using a single solution–immersion process. The modified sponge has stable superhydrophobicity owing to the synergy of triple hydrophobic mechanisms with a maximum water contact angle of 158°. As an absorbent, the modified sponge block exhibits high porosity, outstanding absorption capacity, excellent mechanical properties, and superior physical and chemical stability, enabling its use for the separation of stratified oil–water mixtures via repeated absorption–extrusion processes with a separation efficiency of nearly 100%. Furthermore, as a filter, the crushed, modified sponge powders exhibit a demulsification efficiency ranging from 97.65 to 99.33% for the separation of ideal water-in-oil emulsions under gravity. Finally, the feasibility of these sponges for oilfield applications is established through the demonstration of the continuous separation of an emulsion of brine in crude oil using the modified sponge powders in conjunction with an in-house built apparatus. This work may open a viable pathway for the efficient separation of both stratified and emulsified oil–water mixtures via wettability, and provide a novel strategy for the reuse of waste sponges.