Coral stone-inspired superwetting membranes with anti-fouling and self-cleaning properties for highly efficient oil–water separation

Abstract

Nowadays, the use of separation membranes to deal with oil–water emulsions has gained popularity. However, oil fouling of membrane surfaces during the separation of oil–water emulsion is still a significant challenge. In this study, inspired by the biological coral stone structure, the gel layer was firmly attached to the surface of membrane using a simple co-blending and cross-linking strategy. A super-wetting membrane (PVDF/CD-SA) with a coral stone structure was obtained. The PVDF/CD-SA membrane had a high permeate flux that was 4.2 times higher than that of the original membrane and a high separation efficiency of about 99.2 % for the separation of oil–water emulsion. Furthermore, the membrane had outstanding chemical stability. The fluxes of several different oil-in-water emulsions significantly improved, and the separation efficiencies were as high as 98 %. Moreover, the separation efficiencies and contact angles of the membrane remained unchanged after numerous cycles of use. The membrane exhibited excellent superhydrophilicity in air (instantaneous water wetting in air) and superoleophobicity under water (underwater oil contact angle > 156°). Most importantly, the oil was able to automatically detach from the surface of membrane, resulting in self-cleaning performance. Therefore, this PVDF/CD-SA membrane eliminated the problem of oil adhesion, exhibiting excellent potential for practical applications in oil–water separation.