Comprehensive Exploration of Polyvinyl Alcohol-Tannic Acid Self-Assembled Hydrogel-Coated PVDF Membranes for Efficient Oil-Water Emulsion Separation

With the rapid industrial development worldwide, the volume of oily wastewater, including petroleum spills and industrial effluents, has increased dramatically, posing a threat to ecosystems and human health. Membrane separation technology, known for its advantages of phase-transition-free operation, low energy consumption, and simplicity, has gained rapid popularity in wastewater treatment. This study focused on modifying PVDF membranes using PVA-TA hydrogels with two distinct coordination strategies: TA-Fe³⁺ coordination and APTMS covalent cross-linking. The resulting composite membranes exhibited superhydrophilic/underwater superoleophobic properties with high emulsion flux (3800–6900 and 4200–12,000 Lm^− 2h^− 1bar^− 1) and separation efficiency (> 98.9% and > 99.3%) for various oil-water emulsions. Notably, the stability of the hydrogel network allowed the composite membranes to maintain elevated fluxes (6847.2 and 10266.7 Lm^− 2h^− 1bar^− 1) and separation efficiencies (97.8% and 99.3%) even after 10 cycles for dichloroethylene-water emulsion. The addition of Fe³⁺ and APTMS enhances hydrogel stability and roughness, with APTMS contributing to superior wetting and separation performance. This work provides valuable insights into the impact of different coordination mechanisms on hydrogel-coated membranes, offering a foundation for the development of advanced materials in efficient oil-water separation.