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Uncovering the impact of ‘capsule’ shaped amine-type ligands on Am(III)/Eu(III) separation


Separation of trivalent actinides (An(III)) and lanthanides (Ln(III)) in spent nuclear fuel reprocessing is extremely challenging mainly owing to their similar chemical properties. Two amine-type reagents, tetrakis(2-pyridyl-methyl)-1,2-ethylenediamine (TPEN) and its hydrophobic derivative N,N,N’,N’-tetrakis((4-butoxypyridin-2-yl)methyl)-ethylenediamine (TBPEN) have been identified to possess a selectivity for Am(III) over Eu(III). In this work, the structures, bonding nature, and thermodynamic behaviors of the Am(III) and Eu(III) complexes with these two ligands have been systematically studied via scalar relativistic density functional theory (DFT) calculations. According to Mayer bond order and the quantum theory of atoms in molecules (QTAIM) analyses, interactions between the ligands and metal cations exhibit some degree of covalent character with relatively more covalency for Am(III) complexes. In comparison with TPEN, TBPEN has better extractability but worse separation ability for Am(III) and Eu(III). Four nitrogen atoms in pyridine rings of ligands may be responsible for the different extraction ability of TPEN and TBPEN, while two nitrogen atoms in amine chains of these ligands appear to have more important roles in the separation of Am(III)/Eu(III). These different extraction behaviors may be attributed to the longer and thinner ‘capsule’ shaped TBPEN ligand compared to TPEN. Our study might render new insights into understanding the selectivity of the amine-type ligands toward minor actinides, and pave the way for designing new TPEN derivatives for extraction and separation of An(III)/Ln(III).

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Publication details

The article was received on 08 Aug 2017, accepted on 27 Nov 2017 and first published on 29 Nov 2017

Article type: Paper
DOI: 10.1039/C7CP05381A
Citation: Phys. Chem. Chem. Phys., 2017, Accepted Manuscript
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    Uncovering the impact of ‘capsule’ shaped amine-type ligands on Am(III)/Eu(III) separation

    P. Huang, C. Wang, Q. Wu, J. Lan, G. Song, Z. Chai and W. Shi, Phys. Chem. Chem. Phys., 2017, Accepted Manuscript , DOI: 10.1039/C7CP05381A

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