Crude Oil Fouling-Resistant Dual-Layer Wettability Coalescing Material for Efficient Oil-In-Water Emulsion Separation

Superwetting materials have garnered extensive attention in the demulsification treatment of oil-bearing emulsions, owing to their exceptional oil-in-water emulsions separation performance and antifouling capability. However, such single-layer wetting membranes struggle to simultaneously achieve efficient demulsification and self-cleaning function, usually exhibiting inferior separation performance. Herein, a bilayer heterogeneous wetting membrane was fabricated via plasma etching, which was composed of a superhydrophilic three-dimensional (3D) network polyacrylamide hydrogel skeleton and discontinuous protrusions of hydrophilic Fe2O3 nanocrystals, and was applied for the demulsification of kerosene-in-water (O/W) emulsion. The unbalanced interfacial force derived from the wettability discrepancy between the polymer skeleton and the protrusions facilitated emulsion demulsification, while the protrusions captured and aggregated dispersed oil droplets to form free floating oil. The results demonstrated that the water contact angle (WCA) of the membrane could reach 0° within 0.3 s, and it also exhibited excellent antifouling performance against crude oil. Furthermore, the material retained outstanding hydrophilicity even after undergoing severe damage, including 72 h of chemical corrosion and 500 cycles of abrasion tests. The separation efficiency of the membrane for O/W emulsions reached as high as 99.47%, and remained above 95% after 16 consecutive large-scale separation cycles. This work integrates the structural durability of metal nanoparticles and the antifouling property of superhydrophilic groups, holding enormous potential for the efficient treatment of oil–water emulsions.