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Title: A computational approach to predicting ligand selectivity for the size-based separation of trivalent lanthanides

Abstract

An accurate description of solvation effects for trivalent lanthanide ions is a main stumbling block to the qualitative prediction of selectivity trends along the lanthanide series. In this work, we propose a simple model to describe the differential effect of solvation in the competitive binding of a ligand by lanthanide ions by including weakly co-ordinated counterions in the complexes of more than a +1 charge. The success of the approach to quantitatively reproduce selectivities obtained from aqueous phase complexation studies demonstrates its potential for the design and screening of new ligands for efficient size-based separation.

Authors:
 [1];  [1]
  1. Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)
Publication Date:
Research Org.:
Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)
Sponsoring Org.:
USDOE Office of Nuclear Energy (NE)
OSTI Identifier:
1331079
Grant/Contract Number:
AC05-00OR22725
Resource Type:
Journal Article: Accepted Manuscript
Journal Name:
European Journal of Inorganic Chemistry
Additional Journal Information:
Journal Volume: 2016; Journal Issue: 21; Journal ID: ISSN 1434-1948
Publisher:
ChemPubSoc Europe
Country of Publication:
United States
Language:
English
Subject:
37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY

Citation Formats

Ivanov, Alexander S., and Bryantsev, Vyacheslav S.. A computational approach to predicting ligand selectivity for the size-based separation of trivalent lanthanides. United States: N. p., 2016. Web. doi:10.1002/ejic.201600319.
Ivanov, Alexander S., & Bryantsev, Vyacheslav S.. A computational approach to predicting ligand selectivity for the size-based separation of trivalent lanthanides. United States. doi:10.1002/ejic.201600319.
Ivanov, Alexander S., and Bryantsev, Vyacheslav S.. 2016. "A computational approach to predicting ligand selectivity for the size-based separation of trivalent lanthanides". United States. doi:10.1002/ejic.201600319. https://www.osti.gov/servlets/purl/1331079.
@article{osti_1331079,
title = {A computational approach to predicting ligand selectivity for the size-based separation of trivalent lanthanides},
author = {Ivanov, Alexander S. and Bryantsev, Vyacheslav S.},
abstractNote = {An accurate description of solvation effects for trivalent lanthanide ions is a main stumbling block to the qualitative prediction of selectivity trends along the lanthanide series. In this work, we propose a simple model to describe the differential effect of solvation in the competitive binding of a ligand by lanthanide ions by including weakly co-ordinated counterions in the complexes of more than a +1 charge. The success of the approach to quantitatively reproduce selectivities obtained from aqueous phase complexation studies demonstrates its potential for the design and screening of new ligands for efficient size-based separation.},
doi = {10.1002/ejic.201600319},
journal = {European Journal of Inorganic Chemistry},
number = 21,
volume = 2016,
place = {United States},
year = 2016,
month = 6
}

Journal Article:
Free Publicly Available Full Text
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Cited by: 1work
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  • In this paper, the extraction behavior of a quaternary alkylammonium salt extractant was investigated for its selectivity for trivalent actinides over trivalent lanthanides in nitrate and thiocyanate media. The selectivity was evaluated by solvent extraction experiments through radiochemical analysis of 241Am and 152/154Eu. Solvent extraction distribution and slope-analysis experiments were performed with americium(III) and europium(III) with respect to the ligand (nitrate and thiocyanate), extractant, and metal (europium only) concentrations. Further evaluation of the equilibrium expression that governs the extraction process indicated the appropriate use of the saturation method for estimation of the aggregation state of quaternary ammonium extractants in themore » organic phase. From the saturation method, we observed an average aggregation number of 5.4 ± 0.8 and 8.5 ± 0.9 monomers/aggregate for nitrate and thiocyanate, respectively. Through a side-by-side comparison of the nitrate and thiocyanate forms, we discuss the potential role of the aggregation in the increased selectivity for trivalent actinides over trivalent lanthanides in thiocyanate media.« less
  • A new water-soluble N{sub 4}O{sub 3} tripodal amine phenol ligand, tris(((2-hydroxy-5-sulfobenzyl)amino)ethyl)amine (H{sub 3}TRNS) has been synthesized, and its complexation properties with six lanthanide(III) ions (La, Nd, Gd, Ho, Yb, Lu) have been probed. In water, the ligand coordinates in a tridentate fashion through the three phenolato oxygen atoms to give mono- and bis(ligand) complexes. The bis complexes are proposed to be 7-coordinate containing one bound water as evinced by {sup 17}O NMR experiments on the Dy{sup 3+} complex, while the mono complexes are proposed to have a coordination number of eight or nine. The stepwise formation constants for the 1:1more » and 2:1 (L:M) complexes have been measured. The formation constants show an increasing affinity and an unprecedented selectivity for the heavier lanthanides. Furthermore, the stepwise stability constant for the 2:1 complex is increasingly greater than that for the 1:1 complexes of Gd{sup 3+}, Ho{sup 3+}, and Yb{sup 3+}, while K{sub 1} and K{sub 2} for the 1:1 and 2:1 complexes of Nd{sup 3+} are approximately the same. Solution calorimetry shows that the selectivity for the heavier lanthanides is an enthalpic effect, while the anomalous behavior in formation constants (K{sub 2} > K{sub 1}) is predominantly entropic ({Delta}S{sub 2} > {Delta}S{sub 1}) and is rationalized in terms of solvation of the complexes. 61 refs., 7 figs., 2 tabs.« less
  • The STFICS process, a variation of TRUEX process, was developed for the recovery of Am and Cm from acidic waste solution and the separation of actinides(III) and light lanthanides. The process uses the general TRUEX solvent as the extracting reagent and a DTPA-sodium nitrate solution for selective stripping of actinides(III). The basic flow sheet is composed of four steps: extraction-scrubbing; acid stripping; actinide(III) stripping; and lanthanide stripping. To demonstrate the usefulness of the SETFICS process, a counter current experiment was conducted using a real TRUEX product solution. Americium and curium were successfully recovered with a solution of 0.05 M DTPA-4more » M NaNO{sub 3} (pH 2.0). Although the actinide(III) product solution contained Sm and Eu, the decontamination factor of {sup 144}Ce/{sup 241}Am was 72, and most of the light lanthanides, specifically La, Ce, Pr, Nd, were removed. At least 80% of the lanthanides were separated from the Am and Cm end products. In order to minimize the acidity in the actinide(III) stripping step, the nitric acid which extracted with the trivalent metals was previously removed with a solution of 0.5 M NaNO{sub 3} (pH 2.0) in the acid stripping step.« less
  • The separation of trivalent actinides from the lanthanides using the active extractant in the Cyanex 301 reagent, bis(2,4,4-trimethylpentyl)dithiophosphinic acid, was studied. Specifically, the extractant was studied for an ammonium acetate/acetic acid buffered feed that would result from a transuranic separation process utilizing an ammonium acetate strip solution. Separation factors of 241Am from 154Eu with this extractant, as a function of total acetate concentration and pH, have been measured. Additionally, the extraction behavior of stable La, Ce, Pr, Nd, Sm, and Eu was measured. Separation factors were typically very high for Am from Eu at a pH ranging from 3.8 tomore » 5.8 and a total acetate concentration ranging from 0.2 M to 1.0 M. However, separation factors across the lanthanide series varied considerably and resulted in separation of the lighter lanthanides from the heavier lanthanides at the higher pH’s.« less