Electrospun fibrous membrane with enhanced swithchable oil/water wettability for oily water separation

• Both solution-casting and electrospinning methods are used to fabricate smart membranes.
• Electrospun fibrous membrane owns an extended transition range of oil/water wettability.
• The as-prepared membranes realize many types oil/water separations through regulating the temperature.
• The separations are driven only by gravity and exhibit excellent efficiency higher than 98.5%.
• Electrospun fibrous membrane achieves a higher liquid flux due to the high porosity and the large surface-to-volume ratio.

Smart polymeric surfaces with switchable oil/water wettability are ideal candidates for oil/water separation, which still suffer from significant restrictions in practical separation applications. Appropriate fabrication method should be explored to devise and mass produce smart polymeric membranes. Herein, we prepared two smart membranes through solution-casting method and electrospinning technology, respectively, based on temperature-responsive copolymer poly(methyl methacrylate)-block-poly(N-isopropylacrylamide) (PMMA-b-PNIPAAm). According to the thermo-responsive component PNIPAAm, both membranes exhibited temperature-modulable oil/water wettability. Electrospun fibrous membrane owned an extended transition range of oil/water wettability compared to polymer solution-casting membrane because of its 3D network porous structure of the random entangled fibers. The as-prepared membranes realized gravity-driven oil/water separation with efficiency higher than 98% through regulating temperature. Solution-casting membrane exhibited a water flux of about 6200 L h−1 m−2 and an oil flux of about 1550 L h−1 m−2. By contrast, characteristics of the high porosity and the large surface-to-volume ratio made the electrospun fibrous membrane achieve higher fluxes of about 9400 L h−1 m−2 for water and about 4200 L h−1 for oil. Electrospinning is a powerful and cost-effective method to construct smart membrane with excellent wetting property and separation performance.

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