Janus stainless steel mesh-based membrane with asymmetric wettability for highly efficient gravity-driven oil-water emulsion separation

With the asymmetric wettability of the membrane due to its unique transmission features and functions, the application of oil-water separation achieved rapid development. Nevertheless, their practical application is severely restricted due to poor mechanical durability and low flux in the absence of external pressure. Herein, the Janus ZIF-8/stainless steel mesh/polydopamine (DZIF-8/SSM/PDA) membrane was successfully prepared using electrodeposition , in-situ growth, and shell ligand exchange reaction methods. The Janus membrane surface was created through the combination of 5, 6-dimethylbenzimidazole (DMBIM) modified superhydrophobic nanoparticles ZIF-8 (DZIF), and PDA, exhibiting underwater superoleophobicity (UWOCA 156°), superhydrophobicity (WCA 154°), and excellent anti-oil (light and heavy oil) pollutants ability. By manipulating the molecular repulsion forces on the Janus membrane surface , a stable interfacial hydration layer is created in conjunction with the micro-nano structure. This combination enables the achievement of interfacial demulsification and gravity-driven separation of emulsified oil, according to the Molecular Dynamics (MD) simulation process. The water-in-oil emulsion achieved an oil flux of 601 L m −2  h −1 with a separation efficiency of 99.1 %, while the oil-in-water emulsion demonstrated a water flux of 62 L m −2  h −1 with a separation efficiency of 99.7 %. The Janus DZIF-8/SSM/PDA demonstrated acid and alkali resistance, mechanical stability and reusability , and resistance to E. coli bacteria. Overall, this research anticipates advancing the production of durable asymmetric Janus membranes with superior separation efficiency under gravity, providing a novel solution for oil-water separation.