Insights into neodymium interaction with carboxylate-graphene-like support in presence of nitrate: A comparative DFT investigation

Recently, we demonstrated that carboxylate mesoporous carbon improved the adsorption of rare earth elements as neodymium (Nd). Here, calculations based on Density Functional Theory were carried out to give insight on binding of the Nd with carboxylates. Different phenyl carboxylate-Nd complexes were first identified, considering nitrate and water molecules as ligands, in order to obtain reliable carboxylate-graphene models. The optimized structures are used to compute the binding and complexation energies then the competition for metal between carboxylate group and solvent was analysed. The results, in agreement with the experimental evidence, indicated that the Nd favors the anchored carboxylate groups compared to the bulk water. Findings showed that, the graphene support did not significantly alter the carboxylate-Nd binding energies. The partial charges revealed the coupling electron-withdrawing effect of the nitrate and water oxygens. The binding and complexation energies provided here can be regarded as references for designing of REE chelating sorbents.