Robust and recyclable graphene/chitosan composite aerogel microspheres for adsorption of oil pollutants from water.

Despite recent progress in graphene-based aerogels, challenges such as low mechanical strength and adsorption efficiency are still remaining. Here the reduced graphene oxide (rGO)/chitosan (CS) composite aerogel microspheres (rGCAMs) with center-diverging microchannel structures were developed by electrospraying and freeze-drying method. The optimized rGCAMs exhibit a high Young's modulus of 197 kPa and can support ~75,000 times its own weight, due to the cross-linking of CS by glutaraldehyde. Meanwhile, the rGCAMs can maintain high adsorption capacity for 15 cyclic tests due to its excellent mechanical strength. The oil adsorption kinetics and isotherms of rGCAMs follow the pseudo-second-order kinetic equation and the Langmuir model, respectively. The whole adsorption process is influenced by the oil diffusion in the liquid matrix and also in the intra-particle of aerogel microspheres. Moreover, rGCAMs can also be used to separate both surfactant-stabilized water-in-oil and oil-in-water emulsions through demulsification. The high-strength, recyclable and separation-efficient rGCAMs can be a potential candidate for oily wastewater treatment.