Nucleation-Directed Mineralized Electrospun Nanofiber Membrane for Ultra-Low-Pressure Oil-in-Water Emulsion Separation with Superior Antifouling Performance

The inevitable adhesion and accumulation of oily pollutants on membrane interfaces throughout the oil–water separation processes lead to severe performance degradation, underscoring the urgent need for effective and energy-saving antifouling strategies. Herein, a nucleation-directed mineralization strategy is developed to prepare a Cu 3 (PO 4 ) 2 mineralized nanofiber membrane (PAN/CuP) with a micro/nanoparticulate architecture. By preanchoring copper ions onto carboxyl-functionalized electrospun polyacrylonitrile nanofibers as nucleation sites, a uniform and robust mineralized layer is controllably grown, imparting exceptional surface hydrophilicity and underwater superoleophobicity. The phosphate-rich mineral coating endows the PAN/CuP membrane with strong hydration capability, enabling complete oil detachment without prewetting treatment. Under gravity-driven or ultralow-pressure conditions (∼0.01 MPa), the membrane achieves efficient separation of both immiscible oil–water mixtures and surfactant-stabilized emulsions, with separation efficiencies exceeding 99.4%. Benefiting from its robust antifouling capability, the PAN/CuP membrane stably sustains a high flux of 447.3–763 L m –2 h –1 throughout 300 min of continuous cross-flow filtration of oil-in-water emulsions. The fouled membrane can be readily restored by simple water rinsing, attaining a flux recovery ratio (FRR) > 99.2% and an irreversible fouling ratio below 1%, demonstrating nearly complete fouling reversibility. This work provides a robust and energy-efficient strategy for constructing high-performance mineralized nanofiber membranes, offering new insights into the design of advanced antifouling membranes for practical oily wastewater treatment.