Superoleophilic, Mechanically Strong Electrospun Membranes for Fast and Efficient Gravity-Driven Oil/Water Separation

Separating oil–water mixtures is a common obstacle in many processes from wastewater treatment to biofuel manufacture to cleanup of oil spills. There is an urgent need for new, fast, and simple technologies for such separations. In this work, we describe a simple and practical route for creating superoleophilic electrospun membranes that are capable of selectively passing oil and organic compounds at very high rates in a gravity-driven system while retaining water. To prepare these membranes, we blended a new, highly fluorinated random copolymer (FCP), poly(methyl methacrylate-random-perfluorodecyl methacrylate), P(MMA-r-FDMA), with the commodity polymer poly(vinylidene fluoride) (PVDF) and prepared electrospun membranes from their mixture. Membranes composed of nonwoven fibers with uniform and bead-free morphology were obtained upon electrospinning of PVDF blended with this FCP. The PMMA segments provided anchors to the PVDF matrix, resulting in significant enhancement in the mechanical properties with up to 7 times higher Young’s modulus for the blend membranes. Moreover, the self-organization of the long, pendant FDMA side groups within the PVDF matrix resulted in fluorine-rich, highly hydrophobic and superoleophilic surface. As a result, the FCP-containing membranes exhibited up to 17 times faster permeation of oil and organic solvent, compared with pure PVDF membrane in gravity-driven filtration experiments. Their performance was highly stable during a 70 min continuous gravity-driven filtration experiment for oil/water separation, reflecting their excellent fouling resistant properties. This easy-to-implement and cost-effective approach, combined with the high porosity and re-entrant structure created by the electrospinning, can create membranes with excellent mechanical properties and fouling resistance.