TiO2-ZIF-8@vermiculite superoleophobic membrane with photocatalytic self-cleaning for enhanced oil-water emulsion separation.

Membrane separation is widely used for oily wastewater treatment, but irreversible fouling limits long-term operation. In this study, a TiO2-ZIF-8@VMT/PVDF composite membrane was fabricated through layer-by-layer self-assembly strategy, integrating hierarchical transport regulation with photocatalytic regeneration. TiO2-ZIF-8 nanoparticles introduced into the VMT framework enhanced hydrophilicity, optimized water transport pathways, and provided photocatalytic active sites. The membrane achieved a separation flux up to 4.9 × 103 L m-2 h-1 and over 99.4% separation efficiency for various oil-in-water emulsions. During 3029-min continuous operation, the membrane maintained a separation efficiency of 98.2%, and the fouled membrane recovered its flux and separation performance after UV irradiation. Furthermore, cyclic filtration tests under higher rotational speeds showed flux recovery ratios (FRR) of up to 96.1%. In addition, the composite membrane maintained underwater superoleophobic under various conditions of acid, alkali, salt and high temperature, with separation efficiency remained above 99%. Mechanistic investigations combining radical-scavenging experiments, electron paramagnetic resonance spectroscopy, FTIR analysis, total organic carbon measurements, and wettability were characterized. The self-cleaning behavior from the synergistic contribution of ROS-mediated oxidative transformation of organic foulants and the restoration of a hydrophilic and underwater oil-repellent interfacial state. This study provides a photocatalytic self-regenerative membrane strategy for efficient oil-water separation with enhanced operational stability.