Janus Membranes with Asymmetric Superwettability for High-Performance and Long-Term On-Demand Oil/Water Emulsion Separation

Current single-function superwettable materials are typically designed for either oil removal or water removal and are constrained by oil density, limiting their widespread applications. Janus membranes with opposite wettability on their two surfaces have recently emerged and present attractive opportunities for on-demand oil/water emulsion separation. Here, a combination strategy is introduced to prepare a Janus membrane with asymmetric superwettability for switchable oil/water emulsion separation. A mussel-inspired asymmetric interface introduction cooperating with the sequence-confined surface modification not only brings about an asymmetric superwettability Janus interface but also guarantees an outstanding stable interface and remarkable chemical stability surfaces. Specifically, the superhydrophilic surface with underwater superoleophobicity can separate surfactant-stabilized oil-in-water emulsions. Conversely, other surface displays opposite superhydrophobicity and superoleophilicity to treat surfactant-stabilized water-in-oil emulsions. Significantly, this superwettable Janus membrane presents superior long-term on-demand oil/water emulsion separation without obvious flux decline and high recovery ability because of its superwettability and superior stability. Furthermore, the asymmetric superwettability enhances the interfacial floatability at air–water interfaces, enabling the design of advanced interfacial materials. The as-prepared superwettable Janus membrane has established a cooperated separation system, overcoming the monotony of conventional superwettable membranes and expanding the application of these specialized membranes to oily wastewater treatment.