An unmodified recycled Polyethylene terephthalate (PET) nanofibrous membrane for water-in-oil and oil-in-water emulsions separation

A nanofibrous membrane made of unmodified recycled polyethylene terephthalate (rPET) was fabricated by electrospinning using plastic water bottle as raw materials. Using rPET polymer to fabricate membranes may help limit the discharge of plastic bottle waste into the environment and can treat oily wastewater simultaneously, especially emulsions. The variation in the concentration of rPET polymer and the properties of electrospun nanofibers, such as surface morphology and fiber diameter, had a significant impact on both the efficiency of oil droplet capturing and the surface wettability of the membrane. Water-in-oil emulsions and oil-in-water emulsions were separated using the nanofibrous membranes of different concentrations of rPET polymer, and the separation efficiencies at different concentrations of oil, and oil types were measured. The rPET nanofibrous membrane exhibited a water contact angle of 140.1° and was superoleophilic in air and underwater. The membranes exhibited excellent separation performances: >98% separation efficiency and a flux of more than 6500Lm-2 h-1 for water in hexadecane and octane emulsions; >95% efficiency and a flux of 1509.70Lm-2 h-1 after three separation cycles of water-in-oil emulsions. For oil-in-water emulsions, the separation efficiencies were higher than 95%, and flux was more than 3525.22Lm-2 h-1 for hexadecane octane and heptane in water emulsions, with an efficiency of >87.9% and flux of 4186.20Lm-2 h-1 after three separation cycles. Moreover, the as-prepared membrane exhibited high performance of oil-water separation in harsh conditions, including strong acidic, strong basic, and strong salt solutions, with separation efficiencies of more than 98% and flux of more than 12700Lm-2 h-1. However, as water accumulated on the membrane surface, absorption and separation efficiency and flux were lowered significantly. This suggests the need to enhance the efficiency of the membrane and reduce the chance of water accumulation on the membrane surface.