Theoretical studies on the synergistic extraction of Am and Eu with CMPO-HDEHP and CMPO-HEH[EHP] systems

• Published in: Dalton transactions : an international journal of inorganic chemistry 2018-04, Vol.47 (15), p.5474-5482
• Main Authors: Huang, Pin-Wen, Wang, Cong-Zhi, Wu, Qun-Yan, Lan, Jian-Hui, Song, Gang, Chai, Zhi-Fang, Shi, Wei-Qun
• Format: Article
• Language: English
• ISSN: 1477-9226; 1477-9234
• DOI: 10.1039/c8dt00134k

In recent years, there has been a trend to use synergistic systems of neutral and acidic extractants into a single-solvent formulation to achieve Ln 3+ /An 3+ extraction and separation via simplified processing schemes. In this study, geometrical structures, bonding nature, and thermodynamic stabilities of a series of possible extraction complexes of Am 3+ and Eu 3+ with two neutral-acid synergistic systems (CMPO-HDEHP and CMPO-HEH[EHP]) were theoretically studied using scalar-relativistic density functional theory (DFT). It is found that hydrogen bonds between neutral and acid ligands may greatly influence the Eu 3+ /Am 3+ extraction and separation performance of the two synergistic systems. According to natural bond orbital (NBO) and energy decomposition analyses (EDA), the phosphoryl oxygen atoms of HDEHP or HEH[EHP] have higher affinity for Eu 3+ and Am 3+ than those of the CMPO ligand. Since weak but different extents of covalency exist in Eu- and Am-complexes, Eu 3+ /Am 3+ separation via these two systems may be attributed to the different compositions of interactions between the metal ions and ligands. Thermodynamic analysis shows that the neutral complexes ML(NO 3 ) 2 (M = Eu and Am; L = [CMPO-DEHP] − and [CMPO-EH[EHP]] − ) appear to be the most probable species in the complexation process. Synergistic extraction and separation of Eu 3+ /Am 3+ with CMPO-HDEHP and CMPO-HEH[EHP] systems have been theoretically investigated.