A self-cleaning Cu@MF–PG/GSH membrane for oil–water separation

Abstract

With the development of oil enterprise and petrochemical industry, more and more oily wastewater is generated, which highlights the urgency of oil/water separation. To address the issues of cumbersome membrane preparation and susceptibility to fouling when employing membrane separation techniques, this study proposes a novel simplified method for fabricating modified oil–water separation membranes. Utilising common PVDF membranes as the substrate, the approach involves covalent cross-linking with pyrogallic acid (PG) and glutathione (GSH), coupled with chelation and coordination with copper nanoparticles (Cu NPs). PG can be rapidly oxidized by the Michael addition/Schiff response to generate a mussel-like adhesion layer, and the hydrophilic coating formed by covalent cross-linking with glutathione (GSH) incorporates a huge variety of catechol functional groups, which can form stable superhydrophilic phenolic-aldehyde network coatings through coordination with copper nanoparticles. The Cu@MF–PG/GSH membranes were capable of separating various kinds of stable oil-in-water emulsions with surfactants, and the separation fluxes were large (all fluxes were >779 L m⁻² h⁻¹). Meanwhile, the separation efficiencies were all greater than 99% with an excellent cycle stability (flux recovery >97%). In addition, the self-cleaning property of the Cu@MF–PG/GSH membranes was tested. The outcomes showed that the Cu@MF–PG/GSH membrane could be easily restored after simple water rinsing even when it was contaminated by soybean oil with high viscosity. This suggests the excellent self-cleaning performance of the membrane.