Production, detection, and characterization of transient hexavalent technetium in aqueous alkaline media by pulse radiolysis and very fast scan cyclic voltammetry

Deutsch, Edward; Heineman, William R.; Hurst, Roger W.; Sullivan, James C.; Mulac, William A.; Gordon, S.

doi:10.1039/c39780001038

Cited by 33 publications

(15 citation statements)

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“…2). Namely, hydrated electrons play an important role for the reduction of TcO 4 − , as discussed for pulse radiolysis of TcO 4 − in the literature [8][9][10][11]. The TcO 2 ·nH 2 O colloids suddenly appeared at a higher dose (> 200 kGy) even in the N 2 O-saturated solution (Table 1).…”

Section: Reduction Processes Of Tco 4 −mentioning

confidence: 98%

“…All of these reports described that hexavalent technetium, Tc(VI), was produced by a bimolecular reaction of pertechnetate with hydrated electrons (e aq − ) at a rate constant of (1.3-2.5) × 10 10 M −1 s −1 . However, Deutsch et al [9] and Heller-Grossman et al [10] pointed out the appearance of brownish suspension or precipitate in the electron-irradiated solution at the pulse radiolysis experiments, suggesting the formation of hydrated technetium oxide (TcO 2 ·nH 2 O) as a result of further reduction of Tc(VI). Recently Said et al [12] observed a brown turbid solution by irradiation of aqueous pertechnetate solutions with 60 Co γ rays, and they concluded the formation of Tc(IV) colloids.…”

Section: Introductionmentioning

confidence: 97%

“…Radiolytic processes of Tc have mainly been investigated by pulse radiolysis of pertechnetate (TcO 4 − ) in aqueous solution [8][9][10][11]. All of these reports described that hexavalent technetium, Tc(VI), was produced by a bimolecular reaction of pertechnetate with hydrated electrons (e aq − ) at a rate constant of (1.3-2.5) × 10 10 M −1 s −1 .…”

Section: Introductionmentioning

confidence: 99%

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Radiolytic formation of Tc(IV) oxide colloids

Sekine¹,

Narushima²,

Kino³

et al. 2002

Radiochimica Acta

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Technetium(IV) oxide colloids were radiolytically formed by γ irradiation of aqueous solutions of pertechnetate (TcO 4 − ). Pertechnetate solutions (5.5 × 10 −5 -2.9 × 10 −4 M) were irradiated with bremsstrahlung from an electron linear accelerator at 40 and 17 • C. The color of irradiated solutions gradually changed to brownish black, suggesting the formation of Tc(IV) oxide colloids (TcO 2 ·nH 2 O). A transmission electron microscopy (TEM) analysis showed that the size of colloids distributed around 30 to 130 nm in diameter. The characteristic X-rays from technetium and oxygen were simultaneously detected from colloid particles at the TEM measurements. Roundshaped colloids were produced by irradiation at 40 • C, whereas irregular-shaped colloid particles composed of tiny particles (2 nm in diameter) were produced at 17 • C. The concentration of TcO 4 − in the target solution gradually decreased with an increase of the absorbed dose, corresponding to an increase of the colloid yield. The yield of colloids sharply increased in the solution deaerated by Ar bubbling before irradiation, but strongly suppressed in the solution saturated with oxygen (O 2 ) or nitrous oxide (N 2 O) gas. The fact suggests that hydrated electrons play an important role in the course of the reduction of TcO 4 − and that Tc(IV) oxide colloids were formed via successive disproportionation reactions of Tc(VI) and Tc(V). The formation mechanisms of Tc(IV) oxide colloids are discussed.

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Section: Reduction Processes Of Tco 4 −mentioning

confidence: 98%

Section: Introductionmentioning

confidence: 97%

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

Radiolytic formation of Tc(IV) oxide colloids

Sekine¹,

Narushima²,

Kino³

et al. 2002

Radiochimica Acta

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show abstract

“…Based upon known chemistry, radiolysis of TcO 4 -requires three reducing equivalents and produces Tc(IV) as the radiolysis product: Pertechnetate reacts very quickly with hydrated electrons yielding technetate, TcO 4 2-(equation 3.1) (Pikaev, 1977, Deutsch 1978, Lisbon 1989 (Kissel 1969, Founta 1987. Similarly, in the absence of stabilizing ligands, Tc(V) is known to disproportionate rapidly with a bimolecular rate constant of 2.4×10 3 M -1 s -1 (equation 3.3) (Koltunov 1984a).…”

Section: Resultsmentioning

confidence: 99%

“…Similarly, in the absence of stabilizing ligands, Tc(V) is known to disproportionate rapidly with a bimolecular rate constant of 2.4×10 3 M -1 s -1 (equation 3.3) (Koltunov 1984a). Alternatively, Tc(V) species could be reduced by TcO 4 2-, which is a moderately strong reducing agent, E 0 (TcO 4 -/TcO 4 2-) = -0.64 V vs. NHE (equation 3.4) (Deutsch 1978, Founta 1987. For these reasons, Tc(IV), as TcO 2 •xH 2 O, is the likely radiolysis product in alkaline solutions in the absence of ligands capable of forming Tc(V) or Tc(IV) complexes that are stable at high pH.…”

Section: Resultsmentioning

confidence: 99%