Complexation of Tc(IV) with acetate at varying ionic strengths

Boggs, Mark A.; Dong, Wenyi; Gu, Baohua; Wall, Nathalie A.

doi:10.1524/ract.2010.1757

Cited by 29 publications

(39 citation statements)

References 12 publications

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“…gluconate, EDTA). This explanation for the increase in solubility agrees with published complexation studies, as Tc(IV) was shown to form soluble complexes with oxalic acid [15], acetate [16], and humic substances [17].…”

Section: Introductionsupporting

confidence: 91%

“…Tc(IV) stock solution was prepared according to Hess et al [22] and Boggs et al [16] using a 0.29 M NH 4 TcO 4 (Oak Ridge). The resulting Tc(IV) precipitate was dissolved in concentrated HCl (Fisher) and aliquots were used to prepare a working solution of ca.…”

Section: Methodsmentioning

confidence: 99%

“…For experiments performed near pH 7, TcO(OH) 0 2 is the only Tc(IV) species present in solution [16,17] …”

Section: Data Analysesmentioning

confidence: 99%

“…The previous equation can be rearranged: For experiments carried out at pH 4.5, both TcO(OH) + and TcO(OH) 0 2 species are predicted to be present [16,17] and complexation with both species is expected. Additionally, Tc(IV) complexation with the acetate buffer occurs and has been quantified [16]:…”

Section: Data Analysesmentioning

confidence: 99%

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Complexation of Tc(IV) with EDTA at varying ionic strength of NaCl

Boggs¹,

Islam²,

Dong³

et al. 2012

Radiochimica Acta

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The stability constant for Tc(IV)/EDTA complexes were determined using a solvent extraction technique at varying ionic strength (NaCl) and the specific ion interaction theory model allowed for calculating stability constants at zero ionic strength. The stability constants at zero ionic strength for the formation of the TcOEDTA2− and TcOHEDTA− complexes are 1020.0 ± 0.4 and 1025.3 ± 0.5, respectively. The modeled Tc(IV) solubility was calculated to be 3.9 × 10−7 M at near-neutral pH and in presence of 2.5 mM EDTA, a result found to be in good agreement with published solubility experimental data. Speciation calculations showed that TcOEDTA2− is the predominant species between pH 4 and 7.5 in presence of 0.171 mM EDTA, while TcO(OH)2 0 is predominant in basic solution. These studies show that EDTA has a very strong affinity for complexation with Tc(IV) and can increase the environmental mobility of Tc(IV).

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Section: Introductionsupporting

confidence: 91%

Section: Methodsmentioning

confidence: 99%

“…For experiments performed near pH 7, TcO(OH) 0 2 is the only Tc(IV) species present in solution [16,17] …”

Section: Data Analysesmentioning

confidence: 99%

Section: Data Analysesmentioning

confidence: 99%

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Complexation of Tc(IV) with EDTA at varying ionic strength of NaCl

Boggs¹,

Islam²,

Dong³

et al. 2012

Radiochimica Acta

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“…In the absence of strong organic complexants, the product of Tc(VII) reduction in anaerobic, alkaline, aqueous solution is hydrous Tc(IV) dioxide, TcO 2 -xH 2 O. The solubility of the hydrous Tc(IV) dioxide produced by alkaline pertechnetate reduction has been studied both in simple aqueous solutions and in the presence of various organic ligands (Boggs et al 2010;Gu et al 2011;Warwick et al 2007;Xia et al 2006). Based on this work, it appears unlikely that in the absence of strongly chelating organic ligands, soluble Tc(IV) compounds can account for the concentrations of n-Tc observed in several Hanford tanks.…”

Section: Sy 103mentioning

confidence: 99%

Development of a Chemistry-Based, Predictive Method for Determining the Amount of Non-Pertechnetate Technetium in the Hanford Tanks: FY 2012 Progress Report

Rapko¹,

Bryan²,

Bryant³

et al. 2013

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Executive SummaryThis report describes investigations directed toward understanding the extent of the presence of highly alkaline soluble, non-pertechnetate technetium (n-Tc) in the Hanford Tank supernatants. The goals of this report are to: a) present a review of the available literature relevant to the speciation of technetium in the Hanford tank supernatants, b) attempt to establish a chemically logical correlation between available Hanford tank measurements and the presence of supernatant soluble n-Tc, c) use existing measurement data to estimate the amount of n-Tc in the Hanford tank supernatants, and d) report on any likely, processfriendly methods to eventually sequester soluble n-Tc from Hanford tank supernatants.The work described herein follows on a substantial literature developed in the 1990s and early 2000s that first identified the problem of the presence of n-Tc and led to a tentative identification of the species in at least two Hanford tank waste supernatants. This project attempted to correlate chemically relevant indicators for which quality-valid data exists in the TWINS database suitable for eventual extrapolation to as-yet untested tank supernatants. In addition, two other tangential tasks were undertaken. First, a model was developed that expanded upon a previously published model by Lukens et al. (2001), for the rate of reduction of pertechnetate by radiolysis and inorganic chemical-based processes. Using information obtained from TWINS, this model was applied to the Hanford tank supernatants to identify the rate of pertechnetate reduction in the various Hanford tank supernatants. Second, one proposed species for n-Tc, the complex [(CO) 3 Tc(H 2 O) 3 ] + , was prepared, and initial studies into its spectroscopic signature and chemical stability were performed.From this work, the only acceptable chemically based correlations with data from the TWINS database were that the fraction of n-Tc present negatively correlates with either of two, closely related variables: total dose experienced in the tank, and 137 Cs concentration in the tank supernatants. The observed inverse correlation is counterintuitive, but a possible explanation is discussed. However, the correlation should lend some insight as to which tanks might be tested to further validate and enhance the predictive value of this correlation.As noted above, chemical data, radiolysis constants and known chemical rate constants for the reaction of water radiolysis products with inorganic Hanford tank waste supernatant constituents were used to evaluate the relative rates of pertechnetate reduction in the Hanford tank supernatants. These results are summarized in the report. Interestingly, the reduction rate for pertechnetate is greatest in two tanks, AZ-101 and AZ-102, where the presence of n-Tc is not detected. However, this reduction only concerns the rate of pertechnetate reduction; the speciation of the reduced product is not addressed. Consequently, reduction of pertechnetate to the poorly alkaline-soluble technetium dioxide could ...

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Evaluation of Vanadium(IV) as a Non-radioactive Surrogate for Technetium(IV) by Comparison of Stability Constants for Polyamino Polycarboxylate Ligand Complexation

Omoto

Wall

2017

J Solution Chem

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Complexation of Tc(IV) with acetate at varying ionic strengths

Cited by 29 publications

References 12 publications

Complexation of Tc(IV) with EDTA at varying ionic strength of NaCl

Complexation of Tc(IV) with EDTA at varying ionic strength of NaCl

Development of a Chemistry-Based, Predictive Method for Determining the Amount of Non-Pertechnetate Technetium in the Hanford Tanks: FY 2012 Progress Report

Evaluation of Vanadium(IV) as a Non-radioactive Surrogate for Technetium(IV) by Comparison of Stability Constants for Polyamino Polycarboxylate Ligand Complexation

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