Polyurethane based electrospun membranes for oil-water separation

Abstract

The oil-water separation has found several important industrial applications (e.g., wastewater treatment, oil spill cleanup, etc.). Researchers are searching for very efficient and durable membranes for this purpose. Electrospinning is a promising technique for producing such membranes with tunable structure and physical properties. In this study, polyurethane (PU) alone or in blend with 10percent polystyrene (PS) or poly(vinylidene fluoride-co-hexafluoropropylene) (PVDF-HFP) was used for electrospinning. The optimum conditions were found to be [polymer]=10wt.percent, polymer feed rate=2ml-h, Voltage=21kV, tip to collector distance =21cm, and the drum speed=680rpm. The time of electrospinning was used as a parameter for controlling the thickness and the average pore size diameter of the membranes. The average pore size diameter decreased almost linearly by increasing the thickness. The resulting electrospun membranes were all very hydrophobic and oleophilic in nature with the water contact angle above 130. The hydrostatic pressure head of the membranes increased by decreasing the average pore size diameter. The maximum initial oil separation flux was achieved for the membranes with larger average pore size diameters in the order of: PU9:1PSPUPU9:1PVDF-HFP. The membranes were used for 4 consecutive cycles without any noticeable loss of separation performance. The diesel oil recovery percent after 1 h was found to be above 85percent for the PU9:1PS and PU membranes. A commercially available polytetrafluoroethylene (PTFE) membrane, with thickness 94m and the average pore size diameter 0.45 m, was used for benchmarking.