Theoretically exploring the bonding properties of trivalent transuranic elements with 2‐(2‐amino‐2‐oxyethoxy) acetic acid

Abstract

AbstractIn recent years, the extraction of actinides from high‐level liquid waste is a key step in nuclear waste disposal. However, it is difficult to separate and extract adjacent trivalent actinides An (III) due to similar electron configuration in outer layers. Therefore, studying the law of the bonding between ligands and actinides is essential for designing robust ligands. Here, we demonstrate the in‐group transuranic actinides separation ability of 2‐(2‐amino‐2‐oxoethoxy) acetic acid (HL) through quasi‐relativistic density functional theory (DFT). In the acidic environment of HCl, the extraction of An (III) is governed by cation‐exchange mechanism, forming the complexes [ML2 (H2O)2]+(M = Np, Pu, Am, Cm, Bk) with the deprotonated L− anion during the extraction process. Through calculating the molecular structure and thermodynamic properties of the complexes [ML2 (H2O)2]+, it shows that there exists weak covalent interaction between trivalent transuranic metal ions and ligands L−. Both electrostatic potential and molecular orbital analyses of the ligand L− indicate that the n‐dodecane is an excellent organic solvent for extraction of actinide ions than cyclohexanone. Bonding nature analysis validates that the interaction between An (III) and ligand L− gradually weakens from Np to Cm, and then strengthens from Cm to Bk. The peculiar extraction property of Cm3+ may be connected with its unique electronic structure. Our study may provide reference for understanding the bonding between actinides and ligands, and explore the extraction properties of ligands in different organic solvents, aiming at designing more efficient ligands for the separation of actinides.