Thermodynamic parameters for the complexation of technetium(IV) with EDTA
Abstract
Technetium-99 is a high yield (~6% fission yield) fission product and long-lived (2.13×105year half-life) component of nuclear waste that will be disposed of in a geological repository. Some 99Tc has been released into the environment due to nuclear fuel and weapon production activities at sites such as Hanford, WA. Strongly complexing ligands such as ethylenediamine-N,N,N',N'-tetraacetic acid (EDTA) are known to increase Tc(IV) solubility and mobility in environmental systems and an accurate quantification of the complexation of Tc(IV) with EDTA is important for predicting its behavior in a geological repository. A liquid–liquid extraction system utilizing 0.2 M TOPO in dodecane was used to measure the stability constants of Tc(IV)-EDTA in 0.50 m NaNO3 at variable temperatures (14.0±0.1, 25.0±0.1, and 32.0±0.1°C). The acid dependence of the apparent stability constants in the pCH range of 2.00–2.70 indicated the formation of TcO(EDTA)2-(logβ101=17.9±0.3, 25.0±0.1°C) and a protonated complex TcO(H)(EDTA)-(logβ111=20.5±0.1, 25.0±0.1°C). The associated thermodynamic parameters ΔrG101=-101.7±0.4 kJ·mol-1, ΔrH101=-47±9 kJ·mol-1, ΔrS101=179±36 J·mol-1·K-1, ΔrG111=-117.2±0.3 kJ·mol-1, ΔrH111=-23±5 kJ·mol-1, and ΔrS111=315±63 J·mol-1·K-1(0.50mNaNO3, 25.0±0.1°C) were determined by van’t Hoff analysis. The formation of each Tc(IV)–EDTA complex is exothermic and present favorable entropy terms.
- Authors:
-
- Washington State Univ., Pullman, WA (United States). Dept. of Chemistry
- Washington State Univ., Pullman, WA (United States). Nuclear Science Center
- Publication Date:
- Research Org.:
- Washington State Univ., Pullman, WA (United States)
- Sponsoring Org.:
- USDOE National Nuclear Security Administration (NNSA), Office of Defense Nuclear Nonproliferation
- OSTI Identifier:
- 1529251
- Grant/Contract Number:
- NA0002916
- Resource Type:
- Accepted Manuscript
- Journal Name:
- Radiochimica Acta
- Additional Journal Information:
- Journal Volume: 106; Journal Issue: 12; Journal ID: ISSN 0033-8230
- Publisher:
- de Gruyter
- Country of Publication:
- United States
- Language:
- English
- Subject:
- 11 NUCLEAR FUEL CYCLE AND FUEL MATERIALS; Technetium(IV); EDTA; complexation; stability constants; liquid-liquid extraction; van’t Hoff
Citation Formats
Friend, Mitchell T., Lledo, Cecilia Eiroa, Lecrivain, Lindsey M., Wall, Donald E., and Wall, Nathalie A. Thermodynamic parameters for the complexation of technetium(IV) with EDTA. United States: N. p., 2018.
Web. doi:10.1515/ract-2018-2992.
Friend, Mitchell T., Lledo, Cecilia Eiroa, Lecrivain, Lindsey M., Wall, Donald E., & Wall, Nathalie A. Thermodynamic parameters for the complexation of technetium(IV) with EDTA. United States. https://doi.org/10.1515/ract-2018-2992
Friend, Mitchell T., Lledo, Cecilia Eiroa, Lecrivain, Lindsey M., Wall, Donald E., and Wall, Nathalie A. Tue .
"Thermodynamic parameters for the complexation of technetium(IV) with EDTA". United States. https://doi.org/10.1515/ract-2018-2992. https://www.osti.gov/servlets/purl/1529251.
@article{osti_1529251,
title = {Thermodynamic parameters for the complexation of technetium(IV) with EDTA},
author = {Friend, Mitchell T. and Lledo, Cecilia Eiroa and Lecrivain, Lindsey M. and Wall, Donald E. and Wall, Nathalie A.},
abstractNote = {Technetium-99 is a high yield (~6% fission yield) fission product and long-lived (2.13×105year half-life) component of nuclear waste that will be disposed of in a geological repository. Some 99Tc has been released into the environment due to nuclear fuel and weapon production activities at sites such as Hanford, WA. Strongly complexing ligands such as ethylenediamine-N,N,N',N'-tetraacetic acid (EDTA) are known to increase Tc(IV) solubility and mobility in environmental systems and an accurate quantification of the complexation of Tc(IV) with EDTA is important for predicting its behavior in a geological repository. A liquid–liquid extraction system utilizing 0.2 M TOPO in dodecane was used to measure the stability constants of Tc(IV)-EDTA in 0.50 m NaNO3 at variable temperatures (14.0±0.1, 25.0±0.1, and 32.0±0.1°C). The acid dependence of the apparent stability constants in the pCH range of 2.00–2.70 indicated the formation of TcO(EDTA)2-(logβ101=17.9±0.3, 25.0±0.1°C) and a protonated complex TcO(H)(EDTA)-(logβ111=20.5±0.1, 25.0±0.1°C). The associated thermodynamic parameters ΔrG101=-101.7±0.4 kJ·mol-1, ΔrH101=-47±9 kJ·mol-1, ΔrS101=179±36 J·mol-1·K-1, ΔrG111=-117.2±0.3 kJ·mol-1, ΔrH111=-23±5 kJ·mol-1, and ΔrS111=315±63 J·mol-1·K-1(0.50mNaNO3, 25.0±0.1°C) were determined by van’t Hoff analysis. The formation of each Tc(IV)–EDTA complex is exothermic and present favorable entropy terms.},
doi = {10.1515/ract-2018-2992},
journal = {Radiochimica Acta},
number = 12,
volume = 106,
place = {United States},
year = {Tue Nov 27 00:00:00 EST 2018},
month = {Tue Nov 27 00:00:00 EST 2018}
}
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