Melamine modified graphene hydrogels for the removal of uranium(VI) from aqueous solution

Melamine-modified graphene hydrogels (MA-GH) were successfully synthesized through a simple one-step method. The three-dimensional (3D) porous network of the graphene hydrogel composite was functionalized using melamine with multiple nitrogen-containing functional groups. Based on its unique network structure, large surface area and sufficient active sites, the synthesized 3D hydrogels displayed a high adsorption capacity (404.85 mg g(-1)), high removal rate of uranium(VI) (>90% at ppm level, or similar to 75% in simulated seawater) and large K-d(U) value (8.52 x 10(4) mL g(-1)). The adsorption process was described well using pseudo-second-order kinetics and the Langmuir isotherm model. The thermodynamic parameters indicated that the adsorption process was spontaneous and endothermic. Based on the above results, the MA-GH composites reveal promising potential as an adsorbent for capturing uranium(VI) in aqueous solution and simulated seawater.