Superhydrophilic/air-superoleophobic diatomite porous ceramics for highly-efficient separation of oil-in-water emulsion

Facile, eco-friendly and effective separation of oil-in-water emulsion under various conditions is urgently desired. In this work, novel 3D superhydrophilic/air-superoleophobic diatomite porous ceramics (3DSSPC) with superior separation performance for surfactant-stabilized oil-in-water emulsions were successfully fabricated via a foam gelcasting-freeze drying and subsequent surface modification approach. SiO2 whiskers in-situ generated on the surface of disc-like diatomite particles increased the roughness of the porous ceramics, which, along with the organic film formed on their surface, conferred excellent superhydrophilic and air-superoleophobic properties. The continuous separation efficiency of the 3DSSPC for the surfactant-stabilized edible oil-in-water emulsion (oil concentration of 5 wt%) was higher than 99%, with a flux of 5.06 kg·m−2·s−1 ( 18,200 L·m−2·h−1), more importantly, the separation flux for an industrial oil-in-water emulsion containing suspended particles was as high as 5.69 kg·m−2·s−1 ( 20,500 L·m−2·h−1). In addition, the microstructure, superoleophobicity and separation efficiency of the 3DSSPC changed little even after 20 separation cycles. The good mechanical strength and outstanding chemical stability in strong acidic, alkaline, concentrated salty solutions and at high/low-temperature make the 3DSSPC a promising candidate for future treatments of industrial wastewater containing emulsified oil-in-water liquids.