The Oxidation of Hydroxylamine by Technetium(VII) in Hydrochloric Acid

Abstract

Tc(VII) oxidizes NHaOH^ in HCl Solution by an autocatalytic reaction mechanism which involves a slow reduction to Tc(V) followed by a rapid reduction to Tc(IV). Tc(IV) then reacts with Tc(VII) to produce Tc(V) thus accelerating the Overall oxidation reaction. The rate equation has been determined as: jt,[Tc(VII)][NH30H+] + Ä:,[Tc(VII)][Tc(IV)][H^]where the rate constant of the Tc(VII) reduction reaction (<:,) is 7.6±0.7X 10"^ 1 moi"' min ' and the rate constant of Tc(V) reproportionation (A:^) is 20±2 P mol"^ min"' (both at 80°C and an ionic strength of 4). The corresponding activation energies of these reactions are = 92±3 kj mol"' and £2 = 85± 2 kJ mol"'.

Studies of U(IV) Oxidation Kinetics in Nitric Acid and TBP Phases

“…). These reactions are very slow and are really governed by the well known oxidation reactions of hydroxylamine with HN0 3 and HNO z (see 7) and references therein). Hence, at lower temperatures and acidities TC04-, is essentially stable in the presence of hydroxylamine.…”

“…The slow rate determining reactions are, therefore, considered to be the HN0 3 oxidations of U(IV) and Tc(IV) (Eqs. [7][8]. Kinetic analysis of the experimental data leads to the derivation of a rate equation ll ) where, respectively, kg = (2.8 ± 0.10) xl0-3 11.05 mo r1.05min-1 ; k 9 = 123 ± 10 12.4 mo r 2 .4min-1 at 35°C and Eg = 73 ± 3; E 9 == 86 ± 2 kJmor 1 .…”

The Oxidation of Hydroxylamine by Nitric Acid in the Presence of Technetium(VII)

“…A previous paper [1] reported a kinetic study of the direct reaction between hydroxylamine and technetium(Vn) ions. The reaction was studied in hydrochloric acid to allow the spectrophotometric measurement of Tc(IV) and Tc(V) absorption bands which are either absent or obscured in nitrate solutions and also to eliminate the effects of interfering reactions with nitrous and nitric acids.…”

Kinetics of Technetium Reactions: XV. Tc(IV) Oxidation with Persulfate Ions in HClO4 Solution

“…In our previous papers, we considered features of the redox reactions of Tc(IV), Tc(V), and Tc(VII) ions predominantly in hydrochloric acid solutions, in particular, reduction of Tc(VII) with hydroxyethylhydrazine [2] and hydroxylamine [3]. The results of these studies were summarized in [4].…”

“…On the other hand, the overall reaction rates (W) found from the slopes of the initial portions of the kinetic curves [Tc(IV)]3time at various temperatures 3 The activation energy of the overall reaction calculated from these data by the least-squares method is 77.7 + 8.1 kJ mol !1 .…”