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.
N1 - Publisher Copyright:
© 2022 Taylor & Francis Group, LLC.
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 - chemical speciation
KW - diglycolamide extractant
KW - HEH[EHP]
KW - in-situ spectroscopy
KW - TEHDGA
UR - http://www.scopus.com/inward/record.url?scp=85125912550&partnerID=8YFLogxK
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 -