Whey protein meets proanthocyanidins: An ultra-fouling resistant PVDF membrane for emulsion separation.

Membrane separation technology is widely used in the treatment of oily wastewater because of its advantages such as green and high efficiency. However, after a long period of operation, the contamination resistance of conventional membranes decreases significantly and the apertures are easily clogged by oil droplets. In this study, a stable superhydrophilic micro/nano protein-polyphenol network structure was constructed on the surface of a hydrophobic PVDF membrane using whey protein (WPC) and proanthocyanidin (PC) without the addition of external particles in conjunction with the classical Cassie-Baxter model of wettability. The separation flux and efficiency of crude oil-in-water emulsion with PVDF-WPC-PC membrane could reach 802.55 L·m-2 h-1 and 99.48 %, respectively. The protein-polyphenol network structure remained stable after various stability tests due to the absence of external particle introduction. After cyclic separation experiments, the flux and separation efficiency only decreased by 14 % and 0.39 % compared to the initial performance. The mechanism of constructing protein polyphenol structures is highlighted. The strategy provided in this study offers a new option for the construction of stable hydrophilic coatings.