Structural, Electronic and Thermochemical Study of Interaction Between Lanthanum Trivalent Ion with Diglycolamide Extractants Using Density Functional Theory

Abstract

Diglycolamides have been widely investigated for the high efficient extraction of lanthanide and actinide ions from nuclear wastes. In the present study, we have mainly investigated the structural changes of diglycolamides and their interaction with trivalent lanthanum cation from the structural, electronic and thermodynamical viewpoints, using density functional theory (DFT) approach. In this line, we have assessed comparatively some structural changes in diglycolamide ligand, including displacement of oxygen ether with nitrogen, using methyl substituent and also adding methylene between oxygen ether and carbonyl functional group. The calculated thermodynamical properties indicate that addition of methylene groups between the ether oxygen and carbonyl functional groups decreases the performance of these ligands in the extraction of lanthanum ions. Moreover, our calculated results demonstrate the thermodynamical preference of using n-hexane as solvent in comparison with dodecane that is in agreement with the experimental observations. In the next step, the trend of variations in the calculated bond order of some selected key bonds through the complexation process has been analyzed. Finally, we have calculated and discussed the deformation energies of ligands through the complexation with the lanthanum cation.

Keywords

• diglycolamide extractants
• lanthanum ion
• structural changes
• density functional theory
• thermodynamic functions