Underwater superoleophobic PVA–GO nanofibrous membranes for emulsified oily water purification

Abstract

Accidental oil spills during oil exploration, production and transportation constitute a significant environmental threat, and thus remain a major challenge. Given that, common polymeric membranes often exhibit surface fouling, which limits their long term practical applications and makes it hard to recycle them with efficient flux stability and separation efficiency. Herein, we report a versatile porous structured polyvinyl alcohol (PVA) based nanofibrous membrane (NFM) with graphene oxide (GO), prepared by simple and straightforward electrospinning, to remediate oily water. The PVA–GO NFM was prepared keeping in view an effective pore geometry and selective wettability to facilitate oily water emulsion separation entirely under gravitational force, with a controlled GO ratio and compatibility to avoid aggregation, allowing easy spin ability. The morphology of the PVA NFM was completely changed in the presence of GO due to homogenous distribution with robust mechanical strength and outstanding thermal stability. As a result, the as-prepared PVA–GO NFM achieves a separation efficiency of above 99% for surfactant-free and surfactant-stabilized oily water emulsions with a water flux of approximately 45 and 30 L m⁻² h⁻¹, entirely under gravitational force due to the presence of GO. Furthermore, the PVA–GO NFM maintains its actual selectivity and surface wettability even after recycling, thereby allowing long term applications with almost the same separation efficiency and water flux. The present methodology for membrane fabrication is believed to be an effective energy saving filtration approach, with anti-oil property and reusability, and thus is promising for practical use in water purification and treatment processes, specifically for oily water remediation.