Characterization of the ALSEP Process: Investigating Equilibrium and Intermediate Complexes of the Scrub Stage

Gabriela A. Picayo; Brian D. Etz; Madeleine A. Eddy; Shubham Vyas; Mark P. Jensen

doi:10.1080/07366299.2022.2037222

Characterization of the ALSEP Process: Investigating Equilibrium and Intermediate Complexes of the Scrub Stage

Gabriela A. Picayo, Brian D. Etz, Madeleine A. Eddy, Shubham Vyas, Mark P. Jensen

Workflow and Ecosystem Services

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Abstract

A unique combination of real-time and conventional optical spectroscopy, off-line chemical analyses, and equilibrium solvent extraction measurements were employed to monitor progressive changes in the speciation of the organic-phase complexes of neodymium or americium in the biphasic scrub stage of the Actinide-Lanthanide Separation (ALSEP) solvent extraction process proposed for trivalent actinide/lanthanide separations. Consistent with the findings of other researchers, four unique organic-phase species are identified by three separate methods of multivariate analysis. The organic phase initially contains M(TEHDGA)₂(HEH[EHP])₂(NO₃)₃ complexes. As the ALSEP organic phase is scrubbed with an aqueous malonate buffer, the complex loses HNO₃ to form M(TEHDGA)₂(H(EH[EHP])₂)(NO₃)₂ as the first organic-phase intermediate species. Further contact with the scrub aqueous phase forms a second intermediate species, M(TEHDGA)(H(EH[EHP])₂)₂(NO₃), and eventually a complex containing only HEH[EHP], M{H(EH[EHP])₂}₃ (where TEHDGA = N,N,N’,N’-tetra(2-ethylhexyl)diglycolamide and HEH[EHP] = 2-ethylhexyl phosphonic acid mono-2-ethylhexyl ester). Similar intermediate species were also observed in equilibrium ALSEP organic phases when lower aqueous concentrations of nitric acid (e.g., 0.5 M HNO₃) were used to extract actinides or lanthanides.

Original language	English
Pages (from-to)	654-679
Number of pages	26
Journal	Solvent Extraction and Ion Exchange
Volume	40
Issue number	6
DOIs	https://doi.org/10.1080/07366299.2022.2037222
State	Published - 2022

Funding

This material is based upon work supported by the Department of Energy Office of Nuclear Energy under the Award Number DE-NE0008554.

Keywords

ALSEP
HEH[EHP]
TEHDGA
chemical speciation
diglycolamide extractant
in-situ spectroscopy

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10.1080/07366299.2022.2037222

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title = "Characterization of the ALSEP Process: Investigating Equilibrium and Intermediate Complexes of the Scrub Stage",

abstract = "A unique combination of real-time and conventional optical spectroscopy, off-line chemical analyses, and equilibrium solvent extraction measurements were employed to monitor progressive changes in the speciation of the organic-phase complexes of neodymium or americium in the biphasic scrub stage of the Actinide-Lanthanide Separation (ALSEP) solvent extraction process proposed for trivalent actinide/lanthanide separations. Consistent with the findings of other researchers, four unique organic-phase species are identified by three separate methods of multivariate analysis. The organic phase initially contains M(TEHDGA)2(HEH[EHP])2(NO3)3 complexes. As the ALSEP organic phase is scrubbed with an aqueous malonate buffer, the complex loses HNO3 to form M(TEHDGA)2(H(EH[EHP])2)(NO3)2 as the first organic-phase intermediate species. Further contact with the scrub aqueous phase forms a second intermediate species, M(TEHDGA)(H(EH[EHP])2)2(NO3), and eventually a complex containing only HEH[EHP], M\{H(EH[EHP])2\}3 (where TEHDGA = N,N,N{\textquoteright},N{\textquoteright}-tetra(2-ethylhexyl)diglycolamide and HEH[EHP] = 2-ethylhexyl phosphonic acid mono-2-ethylhexyl ester). Similar intermediate species were also observed in equilibrium ALSEP organic phases when lower aqueous concentrations of nitric acid (e.g., 0.5 M HNO3) were used to extract actinides or lanthanides.",

keywords = "ALSEP, HEH[EHP], TEHDGA, chemical speciation, diglycolamide extractant, in-situ spectroscopy",

author = "Picayo, \{Gabriela A.\} and Etz, \{Brian D.\} and Eddy, \{Madeleine A.\} and Shubham Vyas and Jensen, \{Mark P.\}",

note = "Publisher Copyright: {\textcopyright} 2022 Taylor \& Francis Group, LLC.",

year = "2022",

doi = "10.1080/07366299.2022.2037222",

language = "English",

volume = "40",

pages = "654--679",

journal = "Solvent Extraction and Ion Exchange",

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TY - JOUR

T1 - Characterization of the ALSEP Process

T2 - Investigating Equilibrium and Intermediate Complexes of the Scrub Stage

AU - Picayo, Gabriela A.

AU - Etz, Brian D.

AU - Eddy, Madeleine A.

AU - Vyas, Shubham

AU - Jensen, Mark P.

PY - 2022

Y1 - 2022

N2 - A unique combination of real-time and conventional optical spectroscopy, off-line chemical analyses, and equilibrium solvent extraction measurements were employed to monitor progressive changes in the speciation of the organic-phase complexes of neodymium or americium in the biphasic scrub stage of the Actinide-Lanthanide Separation (ALSEP) solvent extraction process proposed for trivalent actinide/lanthanide separations. Consistent with the findings of other researchers, four unique organic-phase species are identified by three separate methods of multivariate analysis. The organic phase initially contains M(TEHDGA)2(HEH[EHP])2(NO3)3 complexes. As the ALSEP organic phase is scrubbed with an aqueous malonate buffer, the complex loses HNO3 to form M(TEHDGA)2(H(EH[EHP])2)(NO3)2 as the first organic-phase intermediate species. Further contact with the scrub aqueous phase forms a second intermediate species, M(TEHDGA)(H(EH[EHP])2)2(NO3), and eventually a complex containing only HEH[EHP], M{H(EH[EHP])2}3 (where TEHDGA = N,N,N’,N’-tetra(2-ethylhexyl)diglycolamide and HEH[EHP] = 2-ethylhexyl phosphonic acid mono-2-ethylhexyl ester). Similar intermediate species were also observed in equilibrium ALSEP organic phases when lower aqueous concentrations of nitric acid (e.g., 0.5 M HNO3) were used to extract actinides or lanthanides.

AB - A unique combination of real-time and conventional optical spectroscopy, off-line chemical analyses, and equilibrium solvent extraction measurements were employed to monitor progressive changes in the speciation of the organic-phase complexes of neodymium or americium in the biphasic scrub stage of the Actinide-Lanthanide Separation (ALSEP) solvent extraction process proposed for trivalent actinide/lanthanide separations. Consistent with the findings of other researchers, four unique organic-phase species are identified by three separate methods of multivariate analysis. The organic phase initially contains M(TEHDGA)2(HEH[EHP])2(NO3)3 complexes. As the ALSEP organic phase is scrubbed with an aqueous malonate buffer, the complex loses HNO3 to form M(TEHDGA)2(H(EH[EHP])2)(NO3)2 as the first organic-phase intermediate species. Further contact with the scrub aqueous phase forms a second intermediate species, M(TEHDGA)(H(EH[EHP])2)2(NO3), and eventually a complex containing only HEH[EHP], M{H(EH[EHP])2}3 (where TEHDGA = N,N,N’,N’-tetra(2-ethylhexyl)diglycolamide and HEH[EHP] = 2-ethylhexyl phosphonic acid mono-2-ethylhexyl ester). Similar intermediate species were also observed in equilibrium ALSEP organic phases when lower aqueous concentrations of nitric acid (e.g., 0.5 M HNO3) were used to extract actinides or lanthanides.

KW - ALSEP

KW - HEH[EHP]

KW - TEHDGA

KW - chemical speciation

KW - diglycolamide extractant

KW - in-situ spectroscopy

UR - https://www.scopus.com/pages/publications/85125912550

U2 - 10.1080/07366299.2022.2037222

DO - 10.1080/07366299.2022.2037222

M3 - Article

AN - SCOPUS:85125912550

SN - 0736-6299

VL - 40

SP - 654

EP - 679

JO - Solvent Extraction and Ion Exchange

JF - Solvent Extraction and Ion Exchange

IS - 6

ER -

Characterization of the ALSEP Process: Investigating Equilibrium and Intermediate Complexes of the Scrub Stage

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