EPR studies of technetium complexes in frozen solution

Baldas, John; Boas, John F.; Williams, Graham J.

doi:10.1007/bf03162245

Cited by 8 publications

(9 citation statements)

References 25 publications

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“…This view shows that a very broad spectrum, most likely from a spin > 1/2 species, becomes evident at low temperatures, while the spin = 1/2 species centered at g ~ 2, shown in Figure 5.10, is only faintly visible. Baldas et al (1996) reported a similar spectrum for [Bu 4 N] 2 [Tc(IV)Cl 6 ], also in methylene chloride, at 5.7 K.…”

Section: Development Of 99 Tc Epr Characterization Techniquementioning

confidence: 72%

“…But the possibility remains that the triplet state of Tc(V) [TcOCl 5 ] 2might exist; if so, it should generate its own EPR response. Additionally, the pertechnetate reduction in concentrated HCl does not stop when Tc(V) is formed, it proceeds further to the thermodynamically stable [TcCl 6 ] 2-, which has an EPR-active Tc(IV) center (Baldas et al 1996). So this complex system is especially suited to develop the EPR method for Tc characterization and to understand Tc fundamental chemistry.…”

Section: Development Of 99 Tc Epr Characterization Techniquementioning

confidence: 99%

“…When the temperature of the sample was further decreased to 5 K, the g = 1.95 spectrum decreased in relative intensity and the very broad spectrum became more evident, Figure 5.11. (Baldas et al 1996) is reproduced for comparison (black trace). This view shows that a very broad spectrum, most likely from a spin > 1/2 species, becomes evident at low temperatures, while the spin = 1/2 species centered at g ~ 2, shown in Figure 5.10, is only faintly visible.…”

Section: Development Of 99 Tc Epr Characterization Techniquementioning

confidence: 99%

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Speciation and Oxidative Stability of Alkaline Soluble, Non-Pertechnetate Technetium

Levitskaia

Rapko

Anderson

et al. 2014

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Tc(CO) 3 ] + /gluconate complex was considerably slower in the supernatant simulant than in the simple 5 M NaNO 3 /0.5 M NaOH/0.5 M NaGluconate solution. 4. These results indicate that a carbonyl complex is a viable candidate for the source of non-pertechnetate in tank waste. As indicated, testing has identified a range of conditions under which a significant portion of the carbonyl complex is stable for extended periods of time. Preliminary studies have shown a viable route for the formation of this complex under tank waste conditions. Also, since the range of concentration in tank waste varies from less than 0.1% to greater than 50%, the rates of production and destruction under these varying conditions obviously vary dramatically, and as such, the balance of these two reactions will be highly dependent upon tank waste chemistry. 5. A proof-of-principle demonstration corroborating the mechanism and feasibility of [Tc(CO) 3 ] + formation from pertechnetate using CO/H 2 reductant in the presence of an organic chelator and catalytic noble metals in the tank waste simulant was performed. The simulant used was based on the previously used Pretreatment Engineering Platform (PEP) simulant formulation, albeit with altered free hydroxide concentrations and with the addition of some noble metals (simulating fission products) to catalyze any needed reduction of Tc(VII) by hydrogen and gluconate as a reductant/complexant. Reaction conditions were approximately 1300 psi atmosphere, at 80 °C for about 12 days. The bulk of the pertechnetate was reduced following this treatment and the Tc(I)-tricarbonyl/gluconate compound was observed by 99 Tc NMR spectroscopy. The same product can be prepared independently by the reaction of [Tc(CO) 3 ] + with gluconate in water, sodium nitrate, or supernatant simulant solutions. In short, this proof-of-principle test supports the concept of alkaline-soluble, low-valent Tc being formed by pertechnetate reduction under conditions consistent with those found in Hanford tank supernatants, albeit at intentionally high concentrations of carbon monoxide in this first proof-of-principle test. 6. To understand Tc speciation in the alkaline solutions, significant effort was placed on the expansion of the Tc characterization techniques and development of computational approaches to enhance interpretation of the experimental observations. In this work, considerable achievements were made toward verifying that the Tc(I)-tricarbonyl species is a viable candidate for the source of alkaline-soluble, non-pertechnetate Tc in the Hanford tank supernatants. This work confirmed that the Tc species based on the [Tc(CO) 3 ] + center can be obtained by the laboratory synthetic route and that a potential route exists for their production in the alkaline tank wastes. These non-pertechnetate species are sufficiently stable under the conditions associated with Hanford tank supernatants. However, considerable work remains, specifically to achieve control over Tc redox behavior in the alkaline media, and to develop metho...

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Section: Development Of 99 Tc Epr Characterization Techniquementioning

confidence: 72%

Section: Development Of 99 Tc Epr Characterization Techniquementioning

confidence: 99%

Section: Development Of 99 Tc Epr Characterization Techniquementioning

confidence: 99%

See 1 more Smart Citation

Speciation and Oxidative Stability of Alkaline Soluble, Non-Pertechnetate Technetium

Levitskaia

Rapko

Anderson

et al. 2014

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“…Linewidth considerations limit the component of the superhyperfine interaction parallel to the Tc≡N direction to less than 2 × 10 –4 cm –1 . In contrast to this, the EPR spectrum of the analogous [ReNF 4 ] – shows resolved hyperfine couplings of 19 F in the parallel part (quintets with the intensity ratio of 1:4:6:4:1) as well as in the perpendicular part (distorted triplets) …”

Section: Resultsmentioning

confidence: 89%

“…More promising were reactions of “nitridotechnetic(VI) acid”, a black‐brown, polymeric solid of the tentative composition {TcN(OH) 3 } n , which is formed from hydrolysis of Cs 2 [TcN X 5 ] ( X = Cl, Br) salts, and readily dissolves in aqueous hydrofluoric acid. The resulting solutions contain only one paramagnetic species, [TcNF 4 ] – , which gives an intense axially‐symmetric EPR spectrum with well‐resolved ten‐line patterns in the parallel and perpendicular parts (Figure ).…”

Section: Resultsmentioning

confidence: 99%