Ab Initio DFT Study of the Interactions of Americium and Curium Ions with Graphene Oxide

One of the most critical steps in the treatment of spent nuclear fuel is the removal of americium (Am) and curium (Cm) ions from radioactive wastewater. The use of new materials with high surface areas, such as graphene, has been considered a promising solution to this issue. Therefore, understanding the mechanism by which Am and Cm ions are adsorbed onto the graphene surface in aqueous solutions is of paramount importance. In this study, we have investigated 12 complexes formed between americium (Am) and curium (Cm) ions and graphene oxide (GO) using density functional theory (DFT), combined with quasi-relativistic small-core pseudopotentials. The structures, bonding characteristics, and energies of Am-(III) and Cm-(III) complexes with graphene oxide modified by hydroxyl (-OH), carboxyl (-COOH), amide (-CONH), and dimethylamide (-CONMe₂) groups have been explored. It can be observed that the distances between the actinide atom and the oxygen atom in the functional groups on graphene (An-OG) vary significantly across different complexes. The coordination bond in the [Cm-(H₂O)₈]³⁺/GO complex exhibits the shortest bond lengths, suggesting the presence of more stable hydrogen bonds. This indicates that the [Cm-(H₂O)₈]³⁺ ion can be more easily adsorbed onto GO. Furthermore, thermodynamic calculations show that the binding strength of Am ions toward GO modified with hydroxyl and dimethylformamide groups is significantly stronger than that of the complexes with carboxyl and amido groups. These results will inform the development of high-efficiency nanoscale scavengers for radioactive contaminant removal.