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

Abstract

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 ∼75% in simulated seawater) and large K^U_d value (8.52 × 10⁴ 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.