Actinyl-Carboxylate Complexes [AnO2(COOH)n(H2O)m]2–n (An = U, Np, Pu, and Am; n = 1–3; m = 0, 2, 4; 2n + m = 6): Electronic Structures, Interaction Features, and the Potential to Adsorbents toward Cs Ion

摘要

Organic compounds of actinyls and their bonding features have attracted extensive attention in nuclear waste separation due to their characteristics of separating fission products. Herein, detailed studies on the binding sites of [AnO_(2)(COOH)_(n) (H_(2)O)_(m) ]~(2–n ) (An = U, Np, Pu, and Am; n = 1–3; m = 0, 2, 4; 2n + m = 6) complexes toward Cs are predicted by calculation, and their electronic excitation characteristics were illustrated, providing theoretical supports for the design of Cs adsorbents. The quantum theory of atom in molecules and electron localization function have been implemented to analyze the chemical bonding characterization. The covalent character of An–O_(C) bonds become weaker with increasing COOH~(–) ligands, and the covalent interaction in An–O_(C) bonds is more obvious than that in An–O_(H) bonds. Total and partial population density of state suggest that the 2p orbits of O have more significant contribution in the low-energy region atoms and the 6d/5f orbits of An have more significant contribution in the high-energy region. The Cs~(+) best adsorption site on [UO_(2)(COOH)_(2)(H_(2)O)_(2)] and [UO_(2)(COOH)_(3)]~(?) is the adjacent oxalates, and the [UO_(2)(COOH)_(3)]~(?) complexes have better adsorption capacity. Besides, the electronic excitation characteristics of Cs~(+) adsorption on the UO_(2)(COOH)_(2)(H_(2)O)_(2) complex were analyzed by the UV–vis spectrum and hole–electron distribution.