Ultra Fast Oil-Water Separation for Different Viscous Oil Using Flourine-Free, Reusable, Superhydrophobic Polyurethane Sponge.

To exploit new adsorbents for oil-spill cleanup, a superhydrophobic material was fabricated by hightemperature reduced graphene oxide (HRGO) coated on commercial polyurethane (PU) sponge via facile dip-coating process. Compared with chemical reagent reduced graphene oxide, the graphene showed expanded sheets and vast surface area, which ensured the water contact angle of this synthesized sponge reached 150.0±2.5°. In order to break the boundary of poor adhesion of graphene on sponge skeleton, a simple approach of sealed thermal treatment was adopted in our work. And then the high-temperature reduced graphene oxide/polyurethane sponge treated with binary flourine-free organosilanes solution showed superhydrophobicity with high water contact angle (162.4±1.0°). Silanes addition also endowed the resultant sponge with enhanced interfacial adhesion on PU skeleton owing to interconnected structure. The as-prepared sponge displayed excellent adsorption capacity, which was 48-74 times of its own weight for different organic solvents and oils, and no decrease of the adsorption capacity was observed after 20 cycles. Besides, for the very sticky oil, the Joule-heat generated in the sponge by applied voltage could reduce the viscosity of oil. With the assistance of Joule-heat, the silane modified high-temperature reduced graphene oxide/polyurethane sponge achieved effective oil-water separation and greatly speeded up the separation efficiency. Additionally, whether in various temperature or corrosive conditions, the superhydrophobicity of the sponge almost remained stable, which was promising for oil/water treatment.