A novel robust adsorbent for efficient oil/water separation: Magnetic carbon nanospheres/graphene composite aerogel

[Display omitted] •Magnetic carbon nanospheres/graphene composite aerogels (MCNS/NGA) were prepared.•Ammonium citrate was used as reducing agent and nitrogen source for the first time.•The MCNS/NGA exhibit high adsorption capacity and excellent recyclability.•Magnetic separation technology and a continuous adsorption system are employed. Recently, graphene aerogels (GAs) have attracted considerable research attention in oil/water separation owing to their remarkable properties. However, the serious stacking of graphene oxide nanosheets (GO) would lead to low adsorption capacity and poor recyclability. For the first time, with alkaline ammonium citrate as reducing agent and nitrogen source, the point-to-face contact between magnetic carbon nanospheres (MCNS) and graphene sheets was adopted to effectively inhibit the aggregation of graphene sheets. Nitrogen-doped magnetic carbon nanospheres/graphene composite aerogels (MCNS/NGA) were fabricated under weakly alkaline conditions by one-step hydrothermal in-situ electrostatic self-assembling strategy. The aerogels have low density, super-elasticity (up to 95 % compression), high specific surface area (787.92 m2 g−1) and good magnetic properties. Therefore, they exhibit adsorption capacity in the range of 187–537 g g−1 towards various organic solvents and oils, superior to most reported materials to date. In addition, thanks to their good mechanical properties, excellent thermal stability and flame retardancy, they can be regenerated by squeezing, distillation and combustion. More importantly, magnetic control technology can be adopted to realize oriented adsorption and facilitate recycling of organic solvents and oils in extreme environments.