Enhanced coalescence separation of oil-in-water emulsions using electrospun PVDF nanofibers

[Display omitted] •The coalescence membrane was fabricated via electrospinning.•Decreasing the diameters of fibers is beneficial to intercept oil droplets.•The membrane could effectively separate emulsified oily wastewater.•The separation efficiency of the 4-layers unit remained above 98.2%. A novel and high-efficiency coalescence membrane enhanced by nano-sized polyvinylidene fluoride (PVDF) nanofibers based on polyester (PET) substrate was fabricated using electrospinning method. The properties of the electrospun nanofibers such as roughness and surface morphology greatly affected the oil droplet interception efficiency and surface wettability of the membrane. A series of coalescence units were prepared with different layers of nanofibrous membrane and the separation efficiencies at different initial concentrations, flow rates, and oil types were tested. It is very interesting that the obtained nanofibrous membrane exhibited superoleophilicity in air but poor oleophilicity under water, which was beneficial to the coalescence process. The coalescence unit with four membrane layers had excellent performances under different initial concentrations and flow rates. The separation efficiency of the 4-layers unit remained above 98.2% when the initial concentration reached up to 2000 mg·L−1. Furthermore, the unit also exhibited good performance with the increasing oil density and viscosity, which is promising for large-scale oil wastewater treatment.