2007•RadiochemistryRequires access
Tc(VII)-catalyzed oxidation of U(IV) with nitric acid in solution of TBP in n-dodecane
V.S. Koltunov, Robin J. Taylor, V. I. Marchenko, К. Н. Двоеглазов, G. V. Koltunov
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Abstract
Oxidation of U(IV) with nitric acid in 30% solution of TBP in n-dodecane is catalyzed by Tc ions; the rate-determining steps are 3U(IV) + 2Tc(VII) → 3U(VI) + 2Tc(IV) and Tc(IV) + Tc(VII) → Tc(V) + Tc(VI). Oxidation of U(IV) is inhibited by the reaction product, HNO2, which partially binds Tc(IV) ions (TcO2+) in an inert complex. The overall rate equation of U(IV) oxidation is-d[U(IV)]/dt = k 1[U(IV)][Tc][HNO3]−3 − k 4[U(IV)]2[HNO2]2[HNO3]−1, where k 1 = 4.8 ± 1.0 mol21−2 min−1 and k 4 = (2.4 ± 1.0) × 105 12 mol−2 min−1 at 25°C, [H2O] = 0.4 M ([Tc] is the total Tc concentration in the reaction mixture). Water and U(VI) have no effect on the reaction rate.