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Characterization of the ALSEP Process at Equilibrium: Speciation and Stoichiometry of the Extracted Complex

Journal Article · · ACS Omega
 [1];  [2];  [2];  [3]
  1. Colorado School of Mines, Golden, CO (United States). Dept. of Chemistry; Colorado School of Mines
  2. Colorado School of Mines, Golden, CO (United States). Dept. of Chemistry
  3. Colorado School of Mines, Golden, CO (United States). Dept. of Chemistry and Nuclear Science and Engineering Program
+ Show Author Affiliations
We have determined the identity of the complexes extracted into the ALSEP process solvent from solutions of nitric acid. The ALSEP process is a new solvent extraction separation designed to separate americium and curium from trivalent lanthanides in irradiated nuclear fuel. ALSEP employs a mixture of two extractants, 2-ethylhexyl phosphonic acid mono-2-ethylhexyl ester (HEH[EHP]) and N,N,N',N'-tetra(2-ethylhexyl)diglycolamide (TEHDGA) in n-dodecane, which makes it difficult to ascertain the nature of the extracted metal complexes. It is often asserted that the weak acid extractant HEH[EHP] does not participate in the extracted complex under ALSEP extraction conditions (2–4 M HNO3). However, the analysis of the Am extraction equilibria, Nd absorption spectra, and Eu fluorescence emission spectra of metal-loaded organic phases argues for the participation of HEH[EHP] in the extracted complex despite the high acidity of the aqueous phases. The extracted complex was determined to contain fully protonated molecules of HEH[EHP] with an overall stoichiometry of M(TEHDGA)2(HEH[EHP])2·3NO3. Computations also demonstrate that replacing one TEHDGA molecule with one (HEH[EHP])2 dimer is likely energetically favorable compared to Eu(TEHDGA)3·3NO3, whether the HEH[EHP] dimer is monodentate or bidentate.
Research Organization:
Colorado School of Mines, Golden, CO (United States)
Sponsoring Organization:
USDOE Office of Nuclear Energy (NE)
Grant/Contract Number:
NE0008554
OSTI ID:
1614814
Journal Information:
ACS Omega, Journal Name: ACS Omega Journal Issue: 14 Vol. 5; ISSN 2470-1343
Publisher:
American Chemical Society (ACS)Copyright Statement
Country of Publication:
United States
Language:
English

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Related Subjects

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY
Anions
Extraction
Mathematical methods
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