Highly Efficient Hydrogel Oil–Water Separation Membranes Prepared by Superhydrophilic Graphene Oxide Brushes

Due to the discharge of oily wastewater and oil extraction activities, the oil content and soluble pollutants in water bodies are increasing, causing serious damage to the environment. Therefore, materials with superhydrophilicity and underwater superhydrophobicity have attracted much attention in the field of oil–water separation. In this study, a graphene oxide (GO) brush (polyacrylic acid [PAA], grafted on GO) high-efficiency hydrogel oil–water separation membrane with superhydrophilicity in air and superhydrophobicity under water was prepared by regulating the hydrophilicity through nano-microstructures. Vacuum-assisted filtration was utilized to prepare GO brushes into membranes. Due to the good hydrophilicity of PAA chains, grafting them onto GO sheets enhanced the hydrophilicity of the membranes and increased the surface roughness. This modification significantly increased the pure water flux of the membrane (maximum value of 428.56 L m −2 h −1 bar −1 ). With the synergistic effect of hydration capacity and layered nanostructures, the GO-PAA membrane possesses superhydrophobic and underwater superoleophobic properties. As a result, the oil–water separation rate of GO-PAA2 membrane was greater than 99.12%, which could realize the separation of various oil–water emulsions. Compared with the pristine GO membranes, the graphene brush membranes formed after PAA chain-branch polymerization have higher stability and durability, stronger hydrophilicity, higher oil–water separation efficiency, and better application prospects.