Biomimetic hydrophilic modification of poly (vinylidene fluoride) membrane for efficient oil-in-water emulsions separation

Membrane separation is one of the simple and efficient methods for treating oily wastewater. To improve the efficiency of oil-in-water emulsion separation, alkali treatment was used to promote the deposition of Fe (III) on poly (vinylidene fluoride) (PVDF) membranes, and the tannic acid (TA)-glutathione (GSH) hydrophilic coating was produced on the membrane surface by biomimetic coating method under weak alkaline conditions. The PVDF membrane with hydrophilic coating and multi-layered surface structure showed hydrophilic/ underwater superoleophobic. Meanwhile, the permeability and antifouling properties were significantly enhanced. According to the experimental results, the optimized modified membrane (MF-3) had excellent pure water flux (3368.0 ± 94.2 L·m−2·h−1), and oil rejection was 99.3 ± 0.2 % for toluene-in-water emulsion. In addition, after simulated fouling and regeneration by bovine serum albumin (BSA) solution, the flux recovery rate reached 97.0 %. Excellent underwater anti-oil adhesion and antifouling properties help maintain high separation efficiency during multiple filtration cycles. The chemical stability of the modified membranes was demonstrated after 7 d immersion in acid, alkali, and salt solutions, respectively. The superior performances of the membrane are attributed to the constructed hydrophilic coating. This environmentally friendly PVDF membrane modification strategy has great potential for application in oil-in-water emulsion separation and provides a reliable solution for sustainable development.