Demulsification and separation of crude oil-in-water emulsion using superhydrophilic silica-based nanocomposite membranes

Environmental concerns regarding long-time oil spills and oily wastewater discharges have drawn increasingly attention. But up to now, the separation of high-viscosity crude oil-in-water emulsions remains difficult, and the demulsification, aggregation and separation mechanisms of oil-in-water emulsions are still unclear. In this work, a facile strategy is reported to fabricate silica-based superhydrophilic or underwater superoleophobic nanocomposite glass fiber membrane (GFM) via surface grafting method at room temperature. The immobilized epoxy-functionalized SiO2 nanoparticles improve the roughness and decreased the pore size of GFM. The hydrophilic copolymers of acrylic acid and glycidyl methacrylate (P(AA-co-GMA)) are further grafted on the membrane to increase its hydrophilicity, thereby achieving durable and efficient separation of crude oil-in-water emulsion with a separation efficiency of 96.2 +/- 0.4% and a flux of 4725 +/- 62 L center dot m(-2)center dot h(-1). Moreover, by an in-situ observation of oil droplets on the membrane fiber surface, the demulsification of oil-water emulsions and the coalescence of small oil droplets are discovered when the oil-in-water emulsions flowed through the superhydrophilic fiber surface. Owing to the great demulsification capability, the as-prepared nanocomposite GFM is endowed with excellent crude oil-in-water emulsion separation performances.