Density functional theory investigations of the trivalent lanthanide and actinide extraction complexes with diglycolamides

Cong Zhi Wang, Jian Hui Lan, Qun Yan Wu, Yu Liang Zhao, Xiang Ke Wang, Zhi Fang Chai, Wei Qun Shi

Research output: Contribution to journalArticlepeer-review

55 Scopus citations

Abstract

At present, designing novel ligands for efficient actinide extraction in spent nuclear fuel reprocessing is extremely challenging due to the complicated chemical behaviors of actinides, the similar chemical properties of minor actinides (MA) and lanthanides, and the vulnerability of organic ligands in acidic radioactive solutions. In this work, a quantum chemical study on Am(iii), Cm(iii) and Eu(iii) complexes with N,N,N′,N′-tetraoctyl diglycolamide (TODGA) and N,N′-dimethyl-N,N′-diheptyl-3- oxapentanediamide (DMDHOPDA) has been carried out to explore the extraction behaviors of trivalent actinides (An) and lanthanides (Ln) with diglycolamides from acidic media. It has been found that in the 1:1 (ligand:metal) and 2:1 stoichiometric complexes, the carbonyl oxygen atoms have stronger coordination ability than the ether oxygen atoms, and the interactions between metal cations and organic ligands are substantially ionic. The neutral ML(NO3) 3 (M = Am, Cm, Eu) complexes seem to be the most favorable species in the extraction process, and the predicted relative selectivities are in agreement with experimental results, i.e., the diglycolamide ligands have slightly higher selectivity for Am(iii) over Eu(iii). Such a thermodynamical priority is probably caused by the higher stabilities of Eu(iii) hydration species and Eu(iii)-L complexes in aqueous solution compared to their analogues. In addition, our thermodynamic analysis from water to organic medium confirms that DMDHOPDA has higher extraction ability for the trivalent actinides and lanthanides than TODGA, which may be due to the steric hindrance of the bulky alkyl groups of TODGA ligands. This work might provide an insight into understanding the origin of the actinide selectivity and a theoretical basis for designing highly efficient extractants for actinide separation.

Original languageEnglish (US)
Pages (from-to)8713-8720
Number of pages8
JournalDalton Transactions
Volume43
Issue number23
DOIs
StatePublished - Jun 21 2014

ASJC Scopus subject areas

  • Inorganic Chemistry

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