Thermodynamic Features of the Complexation of Neodymium(III) and Americium(III) by Lactate in Trifluoromethanesulfonate Media.
The protonation of lactate has been studied in a variety of electrolyte solutions using microcalorimetry to reveal a distinct medium influence imposed on the thermochemistry of the investigated equilibrium. The thermochemistry of lactate protonation, when studied directly in 1.0 M sodium lactate, agreed well with the studies performed in trifluoromethanesulfonate (triflate). This thermodynamic agreement suggests that the physical chemistry of lactate in the solutions applicable to the TALSPEAK process – a solvent extraction method for separating trivalent actinides from trivalent lanthanides within the scope of used nuclear fuel processing efforts – may be simulated in triflate solutions. Potentiometry, spectrophotometry and microcalorimetry have been subsequently used to study the thermodynamic features of neodymium and americium complexation by lactate using triflate as a strong background electrolyte. Three successive mononuclear lactate complexes were identified for Nd(III) and Am(III). The stability constants for neodymium, log ß1 = 2.60 ± 0.01, log ß2 = 4.66 ± 0.02 and log ß3 = 5.6 ± 0.1, and for americium, log ß1 = 2.60 ± 0.06, log ß2 = 4.7 ± 0.1 and log ß3 = 6.2 ± 0.2, were found to closely agree with the thermodynamic studies reported in sodium perchlorate solutions. Consequently, the thermodynamic medium effect, imposed on the TALSPEAK-related solution equilibria by the presence of strong background electrolytes such as NaClO4 and NaNO3, do not significantly impact the speciation in solution.
- Research Organization:
- Idaho National Lab. (INL), Idaho Falls, ID (United States)
- Sponsoring Organization:
- DOE - NE
- DOE Contract Number:
- DE-AC07-05ID14517
- OSTI ID:
- 992643
- Report Number(s):
- INL/JOU-10-17543; ISSN 1572-8927; TRN: US1007813
- Journal Information:
- Journal of Solution Chemistry, Vol. 39, Issue 8; ISSN 0095-9782
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
38 RADIATION CHEMISTRY, RADIOCHEMISTRY, AND NUCLEAR CHEMISTRY
AMERICIUM COMPLEXES
NEODYMIUM COMPLEXES
LACTATES
THERMODYNAMIC PROPERTIES
TALSPEAK PROCESS
CHEMICAL REACTION KINETICS
ELECTROLYTES
actinides
calorimetry
lanthanides
Talspeak process
thermochemistry