Stability constant determinations for technetium (IV) complexation with selected amino carboxylate ligands in high nitrate solutions

• Published in: Radiochimica acta Vol. 105; no. 8; pp. 621 - 627
• Main Authors: Omoto, Trevor, Wall, Nathalie A.
• Format: Journal Article
• Language: English
• Published: De Gruyter 01.08.2017
• Subjects: aminocarboxylate; complexation; Solvent extraction; Tc(IV)
• ISSN: 0033-8230; 2193-3405
• DOI: 10.1515/ract-2016-2702

The stability constants for Tc(IV) complexation with the ligands IDA, NTA, HEDTA, and DTPA were determined in varied nitrate concentrations using liquid-liquid extraction methods. The determined log β stability constants at 0.5 M NaNO were found to be 9.2±0.3, 10.3±0.3, and 15.3±0.3 for IDA, NTA, and HEDTA, respectively. The log β stability constant for DTPA was determined to be 22.0±0.6. These determined stability constants show a slight decrease in magnitude as a function of increasing NaNO concentration. These stability constants were used to model the total dissolution of Tc(IV) in acidic aqueous solutions in the presence of each ligand. The results of these predictive models indicate that amino carboxylic ligands have a high potential for increasing the aqueous dissolution of Tc(IV); at pH 2.3, 0.01 M ligand yield dissolved Tc(IV) concentrations of 1.42·10 M, 1.33·10 M, 6.07·10 M, 9.65·10 M, for DTPA, HEDTA, NTA, and IDA, respectively.