Layer-by-Layer Construction of Cu2+/Alginate Multilayer Modified Ultrafiltration Membrane with Bioinspired Superwetting Property for High-Efficient Crude-Oil-in-Water Emulsion Separation

Due to highly adhesive property, crude oil is easier to adhere on foul filtration membranes. Separation of crude oil-in-water emulsion is a continuing tough work. Hydrogels with low-adhesive superoleophobicity are ideal materials for modifying filtration membranes to achieve efficient and antifouling separation of crude oil-in-water emulsion. A key challenge in fabricating the hydrogel modified filtration membranes is to design an ultrathin hydrogel layer with sufficient anti-crude-oil-fouling ability and with controllable thickness, thus not blocking the micro- and nanosized membrane pores. Inspired by the novel harsh-environment-tolerant superoleophobicity of alginate-rich seaweed, the construction of an ultrathin Cu2+/alginate hydrogel multilayer with controllable thickness at the nanometer scale on a polymer filtration membrane via a layer-by-layer self-assembly method is achieved. Both the nanosized pores and the high flux of original membrane are well-maintained. The Cu2+/alginate multilayer modified ultrafiltration membrane behaves a biomimetic superhydrophilicity, underwater superoleophobicity, and antifouling ability for crude oil. It is capable of efficiently separating crude oil-in-water emulsion with a high water flux of 1230 L m(-2) h(-1) bar(-1), an ultrahigh efficiency of 99.8%, and an outstanding antifouling and cyclic ability. What's more, the membrane exhibits good salt-tolerance, antibacterial ability, and long-term stability.