Influence of uranyl complexation on the reaction kinetics of the dodecane radical cation with used nuclear fuel extraction ligands (TBP, DEHBA, and DEHiBA)

Cristian Celis Barros; Corey D. Pilgrim; Andrew R. Cook; Stephen P. Mezyk; Travis S. Grimes; Gregory P. Horne

doi:10.1039/d1cp03797h

Influence of uranyl complexation on the reaction kinetics of the dodecane radical cation with used nuclear fuel extraction ligands (TBP, DEHBA, and DEHiBA)

Cristian Celis Barros, Corey D. Pilgrim, Andrew R. Cook, Stephen P. Mezyk, Travis S. Grimes, Gregory P. Horne

Research output: Contribution to journal › Article › peer-review

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Abstract

Specialized extractant ligands - such as tri-butyl phosphate (TBP),N,N-di-(2-ethylhexyl)butyramide (DEHBA), andN,N-di-2-ethylhexylisobutryamide (DEHiBA) - have been developed for the recovery of uranium from used nuclear fuel by reprocessing solvent extraction technologies. These ligands must function in the presence of an intense multi-component radiation field, and thus it is critical that their radiolytic behaviour be thoroughly evaluated. This is especially true for their metal complexes, where there is negligible information on the influence of complexation on radiolytic reactivity, despite the prevalence of metal complexes in used nuclear fuel reprocessing solvent systems. Here we present a kinetic investigation into the effect of uranyl (UO₂²⁺) complexation on the reaction kinetics of the dodecane radical cation (RH˙⁺) with TBP, DEHBA, and DEHiBA. Complexation had negligible effect on the reaction of RH˙⁺with TBP, for which a second-order rate coefficient (k) of (1.3 ± 0.1) × 10¹⁰M⁻¹s⁻¹was measured. For DEHBA and DEHiBA, UO₂²⁺complexation afforded an increase in their respective rate coefficients:k(RH˙⁺+ [UO₂(NO₃)₂(DEHBA)₂]) = (2.5 ± 0.1) × 10¹⁰M⁻¹s⁻¹andk(RH˙⁺+ [UO₂(NO₃)₂(DEHiBA)₂]) = (1.6 ± 0.1) × 10¹⁰M⁻¹s⁻¹. This enhancement with complexation is indicative of an alternative RH˙⁺reaction pathway, which is more readily accessible for [UO₂(NO₃)₂(DEHBA)₂] as it exhibited a much larger kinetic enhancement than [UO₂(NO₃)₂(DEHiBA)₂], 2.6×vs.1.4×, respectively. Complementary quantum mechanical calculations suggests that the difference in reaction kinetic enhancement between TBP and DEHBA/DEHiBA is attributed to a combination of reaction pathway (electron/hole transfervs.proton transfer) energetics and electron density distribution, wherein attendant nitrate counter anions effectively ‘shield’ TBP from RH˙⁺electron transfer processes.

Original language	English
Pages (from-to)	24589-24597
Number of pages	9
Journal	Physical Chemistry Chemical Physics
Volume	23
Issue number	43
DOIs	https://doi.org/10.1039/d1cp03797h
State	Published - Nov 21 2021
Externally published	Yes

Funding

This research has been funded by the US-DOE Assistant Secretary for NE, under the Material Recovery and Waste Form Development Campaign, DOE-Idaho Operations Office Contract DE-AC07-05ID14517 and DE-NE0008659 Nuclear Energy Universities Program (NEUP) grant. The efforts of Cook and the picosecond pulsed electron irradiation experiments performed using the BNL Accelerator Center for Energy Research LEAF facility, were supported by the US-DOE Office of Basic Energy Sciences, Division of Chemical Sciences, Geosciences, and Biosciences under contract DE-SC0012704.

Funders	Funder number
US-DOE	DE-AC07-05ID14517, DE-NE0008659
Basic Energy Sciences
Chemical Sciences, Geosciences, and Biosciences Division	DE-SC0012704

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@article{6c03e5c422a248d5bd334afad5fa79df,

title = "Influence of uranyl complexation on the reaction kinetics of the dodecane radical cation with used nuclear fuel extraction ligands (TBP, DEHBA, and DEHiBA)",

abstract = "Specialized extractant ligands - such as tri-butyl phosphate (TBP),N,N-di-(2-ethylhexyl)butyramide (DEHBA), andN,N-di-2-ethylhexylisobutryamide (DEHiBA) - have been developed for the recovery of uranium from used nuclear fuel by reprocessing solvent extraction technologies. These ligands must function in the presence of an intense multi-component radiation field, and thus it is critical that their radiolytic behaviour be thoroughly evaluated. This is especially true for their metal complexes, where there is negligible information on the influence of complexation on radiolytic reactivity, despite the prevalence of metal complexes in used nuclear fuel reprocessing solvent systems. Here we present a kinetic investigation into the effect of uranyl (UO22+) complexation on the reaction kinetics of the dodecane radical cation (RH˙+) with TBP, DEHBA, and DEHiBA. Complexation had negligible effect on the reaction of RH˙+with TBP, for which a second-order rate coefficient (k) of (1.3 ± 0.1) × 1010M−1s−1was measured. For DEHBA and DEHiBA, UO22+complexation afforded an increase in their respective rate coefficients:k(RH˙++ [UO2(NO3)2(DEHBA)2]) = (2.5 ± 0.1) × 1010M−1s−1andk(RH˙++ [UO2(NO3)2(DEHiBA)2]) = (1.6 ± 0.1) × 1010M−1s−1. This enhancement with complexation is indicative of an alternative RH˙+reaction pathway, which is more readily accessible for [UO2(NO3)2(DEHBA)2] as it exhibited a much larger kinetic enhancement than [UO2(NO3)2(DEHiBA)2], 2.6×vs.1.4×, respectively. Complementary quantum mechanical calculations suggests that the difference in reaction kinetic enhancement between TBP and DEHBA/DEHiBA is attributed to a combination of reaction pathway (electron/hole transfervs.proton transfer) energetics and electron density distribution, wherein attendant nitrate counter anions effectively {\textquoteleft}shield{\textquoteright} TBP from RH˙+electron transfer processes.",

author = "{Celis Barros}, Cristian and Pilgrim, {Corey D.} and Cook, {Andrew R.} and Mezyk, {Stephen P.} and Grimes, {Travis S.} and Horne, {Gregory P.}",

note = "Publisher Copyright: {\textcopyright} the Owner Societies 2021.",

year = "2021",

month = nov,

day = "21",

doi = "10.1039/d1cp03797h",

language = "English",

volume = "23",

pages = "24589--24597",

journal = "Physical Chemistry Chemical Physics",

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publisher = "Royal Society of Chemistry",

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Influence of uranyl complexation on the reaction kinetics of the dodecane radical cation with used nuclear fuel extraction ligands (TBP, DEHBA, and DEHiBA). / Celis Barros, Cristian; Pilgrim, Corey D.; Cook, Andrew R. et al.
In: Physical Chemistry Chemical Physics, Vol. 23, No. 43, 21.11.2021, p. 24589-24597.

Research output: Contribution to journal › Article › peer-review

TY - JOUR

T1 - Influence of uranyl complexation on the reaction kinetics of the dodecane radical cation with used nuclear fuel extraction ligands (TBP, DEHBA, and DEHiBA)

AU - Celis Barros, Cristian

AU - Pilgrim, Corey D.

AU - Cook, Andrew R.

AU - Mezyk, Stephen P.

AU - Grimes, Travis S.

AU - Horne, Gregory P.

PY - 2021/11/21

Y1 - 2021/11/21

N2 - Specialized extractant ligands - such as tri-butyl phosphate (TBP),N,N-di-(2-ethylhexyl)butyramide (DEHBA), andN,N-di-2-ethylhexylisobutryamide (DEHiBA) - have been developed for the recovery of uranium from used nuclear fuel by reprocessing solvent extraction technologies. These ligands must function in the presence of an intense multi-component radiation field, and thus it is critical that their radiolytic behaviour be thoroughly evaluated. This is especially true for their metal complexes, where there is negligible information on the influence of complexation on radiolytic reactivity, despite the prevalence of metal complexes in used nuclear fuel reprocessing solvent systems. Here we present a kinetic investigation into the effect of uranyl (UO22+) complexation on the reaction kinetics of the dodecane radical cation (RH˙+) with TBP, DEHBA, and DEHiBA. Complexation had negligible effect on the reaction of RH˙+with TBP, for which a second-order rate coefficient (k) of (1.3 ± 0.1) × 1010M−1s−1was measured. For DEHBA and DEHiBA, UO22+complexation afforded an increase in their respective rate coefficients:k(RH˙++ [UO2(NO3)2(DEHBA)2]) = (2.5 ± 0.1) × 1010M−1s−1andk(RH˙++ [UO2(NO3)2(DEHiBA)2]) = (1.6 ± 0.1) × 1010M−1s−1. This enhancement with complexation is indicative of an alternative RH˙+reaction pathway, which is more readily accessible for [UO2(NO3)2(DEHBA)2] as it exhibited a much larger kinetic enhancement than [UO2(NO3)2(DEHiBA)2], 2.6×vs.1.4×, respectively. Complementary quantum mechanical calculations suggests that the difference in reaction kinetic enhancement between TBP and DEHBA/DEHiBA is attributed to a combination of reaction pathway (electron/hole transfervs.proton transfer) energetics and electron density distribution, wherein attendant nitrate counter anions effectively ‘shield’ TBP from RH˙+electron transfer processes.

AB - Specialized extractant ligands - such as tri-butyl phosphate (TBP),N,N-di-(2-ethylhexyl)butyramide (DEHBA), andN,N-di-2-ethylhexylisobutryamide (DEHiBA) - have been developed for the recovery of uranium from used nuclear fuel by reprocessing solvent extraction technologies. These ligands must function in the presence of an intense multi-component radiation field, and thus it is critical that their radiolytic behaviour be thoroughly evaluated. This is especially true for their metal complexes, where there is negligible information on the influence of complexation on radiolytic reactivity, despite the prevalence of metal complexes in used nuclear fuel reprocessing solvent systems. Here we present a kinetic investigation into the effect of uranyl (UO22+) complexation on the reaction kinetics of the dodecane radical cation (RH˙+) with TBP, DEHBA, and DEHiBA. Complexation had negligible effect on the reaction of RH˙+with TBP, for which a second-order rate coefficient (k) of (1.3 ± 0.1) × 1010M−1s−1was measured. For DEHBA and DEHiBA, UO22+complexation afforded an increase in their respective rate coefficients:k(RH˙++ [UO2(NO3)2(DEHBA)2]) = (2.5 ± 0.1) × 1010M−1s−1andk(RH˙++ [UO2(NO3)2(DEHiBA)2]) = (1.6 ± 0.1) × 1010M−1s−1. This enhancement with complexation is indicative of an alternative RH˙+reaction pathway, which is more readily accessible for [UO2(NO3)2(DEHBA)2] as it exhibited a much larger kinetic enhancement than [UO2(NO3)2(DEHiBA)2], 2.6×vs.1.4×, respectively. Complementary quantum mechanical calculations suggests that the difference in reaction kinetic enhancement between TBP and DEHBA/DEHiBA is attributed to a combination of reaction pathway (electron/hole transfervs.proton transfer) energetics and electron density distribution, wherein attendant nitrate counter anions effectively ‘shield’ TBP from RH˙+electron transfer processes.

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U2 - 10.1039/d1cp03797h

DO - 10.1039/d1cp03797h

M3 - Article

AN - SCOPUS:85118998289

SN - 1463-9076

VL - 23

SP - 24589

EP - 24597

JO - Physical Chemistry Chemical Physics

JF - Physical Chemistry Chemical Physics

IS - 43

ER -

Influence of uranyl complexation on the reaction kinetics of the dodecane radical cation with used nuclear fuel extraction ligands (TBP, DEHBA, and DEHiBA)

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