The influence of f-elements' oxidizing potential and ion charge on their stability in aqueous alkaline solution

Abstract

Abstract The data published on values of redox potentials E of heptavalent Np, Pu, Am, Ru and Mn and octavalent Ru and Pu were analyzed. The half-life (τ 1/2) for reduction reactions of heptavalent metal by water in aqueous alkaline solutions was also analyzed. The decrease in the half life stability of actinide in water with the redox potential for 3− charged anions of Np(VII), Pu(VII), and Am(VII) was found. At the same potential, a charge decrease from 3− to 1−reduces the stability approximately two fold. For the redox couple Pu(VIII)/Pu(VII), the estimated value is E > 1.15  V/NHE. If Pu(VIII) existed as PuO4, it would be very unstable (τ 1/2 ≈  × 102 s) in 1 M NaOH. For the anionic forms of Pu(VIII), PuO4(OH)2 2− and PuO6 4−, the half life was estimated to be very low (τ 1/2 < 1 s).