Electrosorption of uranium(VI) by highly porous phosphate-functionalized graphene hydrogel

In the present work, we reported the preparation of a highly porous phosphate-functionalized graphene (HGP) hydrogel electrode material by a two-step process for uranium (U(VI)) electrosorption. The extra pores were pre-created on graphene nanosheets by a simple H2O2 etching reaction, and then the as-formed holy graphene nanosheets (HG) were assembled into a 3D macrostructure using phytic acid as both gelator and modifier. The interconnected 3D network structure with the hierarchical pores, as well as the abundant phosphate groups, endowed the HGP hydrogel with superior wettability and electrochemical properties compared to pristine graphene. From the results of electrosorption experiments towards U(VI), the kinetics equilibrium of HGP electrode could be reached within 21 min, and its maximum adsorption capacity was up to 545.7 mg g−1 at 1.2 V and pH 5.0. Furthermore, the HGP electrode showed high selectivity towards U(VI) in the presence of other competitive metal ions. Meanwhile, it also exhibited the feasibility of regeneration with an acceptable reduce of 7.5% in removal ratio after six cycles.