Electrospun Polyacrylonitrile-Fluorinated Polyurethane/Polysulfone Nanofiber Membranes for Oil–Water Separation

Electrospun nanofiber membranes exhibit efficient oil–water separation performance, owing to their fine and controllable fiber diameters. However, the three-dimensional dense stacking of nanofibers leads to low porosity, decreasing the oil flux in oil–water separation. Here, a composite nanofiber membrane with a dual-scale structure was designed to achieve a high oil–water separation efficiency and high oil flux simultaneously. In detail, a dense polyurethane/fluorinated polyurethanes (PAN-FPU) nanofiber layer with a fine fiber diameter (150 nm) and a small pore size (3–4 μm) was combined with a fluffy polysulfone (PSF) nanofiber layer with a coarse diameter (1200 nm) and a large pore size (8–9 μm). Using the PAN-FPU nanofiber layer as the inlet layer, modular electrospinning equipment was used to prepare dual-scale nanofiber membranes with a high oil–water separation efficiency and high flux in one step. When the fiber ratio of PAN-FPU/PSF was 1:2, the resulting composite nanofiber film could achieve a separation efficiency of 99.58% and an oil flux of 4630 L m–2 h–1 for an oil–water mixture. For a water-in-oil emulsion, the separation efficiency and oil flux reached 99.37% and 1124 L m–2 h–1, respectively. In addition, the separation efficiency and flux of the biscale nanofiber membrane were simulated by establishing a fluid model, and the simulation results confirmed that the fiber membrane had excellent separation performance. Dual-scale composite nanofiber membranes have potential applications in the field of oily wastewater treatment and locomotive filters compared with monolayer membranes.