A graphene–melamine-sponge for efficient and recyclable dye adsorption

Graphene sponges have attracted extensive interest as adsorbents. However, the hydrophobic nature of graphene hinders the submergence of graphene sponge into the water solution. In the present study, we developed a graphene–melamine-sponge (GMS) that can readily submerge into water solution with the help of a superhydrophilic melamine skeleton and investigated its adsorption behaviors for methylene blue (MB) and orange G (OG). The obtained GMS efficiently adsorbed methylene blue with competitive capacity. Isotherm analysis indicated that the adsorption corresponded to the Langmuir isotherm model in a monolayer manner. The maximum adsorption capacities for MB and OG obtained from the Langmuir isotherm equation are 286.5 mg g−1 and 80.51 mg g−1, respectively. Kinetic studies showed that the adsorption followed a pseudo-second-order kinetics model. The as-prepared GMS could be easily regenerated and maintained 95% adsorption capacity after 10 cycles.