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A novel highly selective ligand for separation of actinides and lanthanides in the nuclear fuel cycle. Experimental verification of the theoretical prediction.

Abstract

We have predicted earlier1 by DFT simulation that tridentate O,N,O-donor cyclic dilactams (B) belonging to the family of pyridine-2,6-dicarboxamides have to be much more selective and efficient extractants for lanthanides and actinides separation than open-structure pyridine-2,6-dicarboxamides due to the higher degree of "ligand preorganization”. In the present work, three new ligands of type (B) were synthesized. Extraction experiments showed that, in line with the data from DFT simulation, these ligands have 5–6-fold higher selectivity for the separation of Am3+/Eu3+ pair and provide distribution coefficients D which are by three orders of magnitude higher than those for the related parent ligands with open structure. Determination of the solvate numbers N for Eu3+ and Am3+ cations by the slope analysis has shown that the stoichiometry of complexes, in the form of which these ions pass from aqueous into organic phase, depends to a considerable extent on the polarity of organic solvent. Strongly polar solvents (ϵ>20) extract these cations mainly in the form of 1:1 complexes LM(NO3)3 having according to the DFT simulation the largest dipole moments (μ = 18,6 ÷ 19,7 D). The solvents of low polarity (ϵ≤10) extract these cations mainly in the form of less polar 2:1 complexes L2M(NO3)3 (μ ≈ 1,6 D). For solvents of intermediate polarity fractional values of solvate numbers were obtained which indicates the coexistence of complexes LM(NO3)3 and L2M(NO3)3 in the organic phase.

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Publication details

The article was received on 21 Mar 2017, accepted on 01 Jul 2017 and first published on 03 Jul 2017


Article type: Paper
DOI: 10.1039/C7DT01009E
Citation: Dalton Trans., 2017, Accepted Manuscript
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    A novel highly selective ligand for separation of actinides and lanthanides in the nuclear fuel cycle. Experimental verification of the theoretical prediction.

    Y. A. Ustynyuk, S. N. Kalmykov, M. Alyapyshev, V. Babain, H. V. Lavrov, S. S. Zhokhov, P. I. Matveev, I. P. Gloriozov, L. I. Tkachenko, I. G. Voronaev and N. A. Ustynyuk, Dalton Trans., 2017, Accepted Manuscript , DOI: 10.1039/C7DT01009E

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