Fabrication of a Superhydrophilic and Underwater Superoleophobic Membrane via One-Step Strategy for High-Efficiency Semicoking Wastewater Separation

Hydrophilic polyvinylidenefluoride (PVDF) mem-branes can effectively separate the low oil content in semicokingwastewater. It is important to develop a stable superhydrophilicPVDF membrane with high oil rejection. Here, we developed aone-step strategy based on a polyphenol netlike structure coatingto achieve the conversion of commercial membranes fromhydrophobic to superhydrophilic; namely, the codeposition of 2-propenamide,N-[2-(3,4-dihydroxyphenyl)ethyl] (DMA) and 3-aminopropyltriethoxysilane (APTES) in aqueous solution. ATR-FTIR and XPS technologies proved that the coating successfullyadhered to the PVDF membrane. The pure waterflux of thedeveloped membrane was 17 270 L m-2h-1bar-1. When treatingsimulated semicoking wastewater with low oil content, thepermeateflux and the oil content of thefiltrate were 5500 L m-2h-1bar-1and <6.5 mg L-1, respectively. The modified PVDFmembrane showed perfect wetting performance. The permeationflux of the real semicoking wastewater cycled 9 times was stable at4530 L m-2h-1bar-1and the oil content of thefiltrate was <12.5 mg L-1. This work emphasizes a simple way to designsuperhydrophilic membranes for the separation of low-oil content emulsion, which will be promising for treating semicokingwastewater.