A biomimetic beetle-like membrane with superoleophilic SiO2-induced oil coalescence on superhydrophilic CuC2O4 nanosheet arrays for effective O/W emulsion separation.

It is highly attractive to develop highly efficient oil-in-water (O/W) emulsion separation technologies for promoting the oily wastewater treatment. Herein, a novel inversely Stenocara beetle-like hierarchical structure of superhydrophobic SiO2 nanoparticle-decorated CuC2O4 nanosheet arrays were prepared on copper mesh membrane by bridging polydopamine (PDA) to make a SiO2/PDA@CuC2O4 membrane for substantially enhanced separation of O/W emulsions. The superhydrophobic SiO2 particles on the as-prepared SiO2/PDA@CuC2O4 membranes were served as localized active sites to induce coalescence of small-size oil droplets in oil-in-water (O/W) emulsions. Such innovated membrane delivered outstanding demulsification ability of O/W emulsion with a high separation flux of 2.5 kL⋅m-2⋅h-1 and its filtrate's chemical oxygen demand (COD) being 30 and 100 mg⋅L-1 for surfactant-free emulsion (SFE) and surfactant-stabilized emulsion (SSE), respectively, and also exhibited a good anti-fouling performance in cycling tests. The innovative design strategy developed in this work broadens the application of superwetting materials for oil-water separation and presents a promising prospect in practical oily wastewater treatment applications.