Heterogeneous-wettability PVDF membrane with slit-shaped pores for efficient gravity-driven oil/water separation

Developing highly efficient gravity-driven membranes for oily wastewater remediation remains a significant challenge, primarily because of insufficient permeation flux and severe membrane fouling. Herein, a novel PVDF membrane was developed via a facile one-step phase inversion method, employing Pluronic F127 and a star-like fluorinated copolymer, poly(ethylene glycol) methacrylate- block -poly(2,3,4,5,6-pentafluorostyrene) (PEGMA- b -PPFS), as additives. The resulting membrane surface featured continuous hydrophilic domains enriched with Pluronic F127, discrete low-surface-energy (LSE) micro-islands composed of PEGMA- b -PPFS, and in situ formed slit-shaped pores. This multi-level heterogeneous wetting architecture endowed the PVDF membrane with fouling-resistance and fouling-release capabilities. Meanwhile, the slit-shaped pores surrounding the LSE micro-islands were capable of enabling rapid water penetration, thereby counteracting the potential negative impact of hydrophobic LSE micro-islands on membrane permeability. As a result, the permeability and antifouling performance of the PVDF membrane were significantly enhanced during oil/water separation. Driven solely by gravity, the maximum permeation flux reached 330.9 L m⁻² h⁻¹, demonstrating a tenfold improvement relative to that of the control PVDF membrane. The flux decline rate was only 16.5%, while the recovery rate approached 100%. Moreover, the novel membrane exhibited excellent separation efficiency (>99.0%), robust stability and reusability during long-term operation, indicating great application potential for energy-saving oily wastewater remediation.