Interactions of Tc(IV) with citrate in NaCl media

Abstract

Technetium / Citrate / Complexation / Solvent extraction / PHREEQCSummary. This paper presents the experimental determination of the stability constant for the citrate complexes with TcO(OH) + and TcO(OH) 2 0 at different ionic strengths (NaCl), using a solvent extraction method. Data show that the stability constants for the formation of TcO(OH)Cit 2− and TcO(OH) 2 Cit 3− are 10 7.5±0.2 and 10 2.8±0.2 , respectively, at zero ionic strength, with an average of 10 6.5±0.3 and 10 2.8±0.2 , respectively, in the 1.0-3.0 M ionic strength range. PHREEQC calculations based on these stability constants show that the TcO(OH)Cit 2− is the predominant species between pH 3 and 8 and that 50 mM citrate leads to a Tc(IV) solubility of 2 × 10 −5 M at pH 5.

Re(VII) diffusion in bentonite: Effect of organic compounds, pH and temperature

“…22 concentrations of organic compounds including citrate and oxalic acid are also found in several of 3 the tanks at Hanford (Xia et al, 2006). They could have an important effect on the migration of 4 radionuclides (RN) by forming water soluble complexes (Boggs et al, 2011;Wall et al, 2013), 5 enhancing their solubility (Gu et al, 2011;Reinoso Maset et al, 2006) and modifying the surface 6…”

“…Tc(IV), can be complexed with citrate (Wall et al, 2013), ethylenediaminetetraacetic acid (EDTA) 8 (Boggs et al, 2013;Gu et al, 2011), oxalate (Xia et al, 2006), acetate (Boggs et al, 2010) and 9 humic substances (Boggs et al, 2011;Gu et al, 2011), increasing the solubility of TcO 2 (s) (Gu et 10 al., 2011). The solubility of Re(IV)-EDTA complexes was also found to be higher than that of 11 Re(VII) (Corkhill et al, 2013).…”

Technetium Complexation with Multidentate Carboxylate-Containing Ligands: Trends in Redox and Solubility Phenomena

“…Solid and dotted lines correspond to the thermodynamically calculated solubility of TcO 2 (am,hyd) under different solution conditions based on values from the literature (Table S3). ,,− Gray dashed lines represent the LSC detection limits (DL LSC) for the experimental analyses, and all error bars are either represented or contained within data symbols.…”

“…One Formation Constant for the Tc-Citrate System Selected from Wall et al 9 No values for Tc−citrate complexation were selected within ThermoChimie or discussed within the NEA-TDB. Wall et al 9 performed solvent extraction studies from pH 4 to 7 to determine the formation constants for two Tc−citrate complexes�TcO(OH)(Cit) 2− and TcO(OH) 2 (Cit) 3− �which were subsequently corrected for ionic strength using the specific ion-interaction theory (SIT). The formation constants for these complexes were derived using the reactions TcO(OH) + + Cit 3− ↔ TcO(OH)-(Cit) 2− and TcO(OH) 2 (aq) + Cit 3− ↔ TcO(OH) 2 (Cit) 3− , respectively.…”

Influence of Natural and Synthetic Organic Ligands on the Stability and Mobility of Reduced Tc(iv)

“…Results are presented in a paper currently in preparation (Boggs et al, 2012a) that will be submitted at the beginning of the 2012 calendar year. [4] [1] (Boggs et al, 2010) [2] (Wall and Karunathilake, 2011) [3] (Boggs et al, 2011a) [4] (Boggs et al, 2011b) The quantification of Tc(IV) complexation with soluble organic ligands, as described above, is of particular interest because ligand complexation lead to an increase of the Tc(IV) solubility. PHREEQC calculations, using the stability constants generated via this work, allowed to show such increase.…”