Superwetting electrospun fibrous membrane for energy-efficient long-term oil-in-water emulsion separation

Nanofibrous membranes hold great promise for water purification, yet their performance is often compromised by irreversible membrane fouling and structural instability under applied pressure, which lead to flux decline and poor separation efficiency. To address these challenges, developing membranes capable of energy-efficient, gravity-driven (or ultra-low pressure) separation with robust anti-fouling properties is highly desirable. In this study, a novel SiO 2 @PVDF-HFP electrospun fibrous membrane with superhydrophilicity/underwater superoleophobicity was developed via electrospinning followed by electrostatic-assisted in situ growth of a SiO 2 nanocoating. This approach ensured a uniform and stable silica layer, which is critical for maintaining performance under low driving pressures. The membrane achieved highly efficient separation of diverse oil-in-water emulsions under gravity, with emulsion separation fluxes ranging from 336 to 605 L m −2 h −1 and separation efficiencies above 99 %. Thanks to the uniform silica coating, the membrane maintained its structural integrity and separation performance even under harsh conditions, due to its enhanced mechanical robustness and chemical stability. In a 6 h continuous cross-flow separation test under an ultra-low pressure, the membrane demonstrated excellent operational stability, with over 97.6 % flux recovery and separation efficiency remaining above 99 %. This study not only demonstrates a viable approach to developing high-performance membranes but also highlights the significant energy-saving potential of separation processes operating under gravity or ultra-low pressure for sustainable oily wastewater treatment.