A highly efficient in situ redox stabilization strategy for Am–Cm separation using AgBiO3

Abstract

AgBiO₃ is reported for the exclusive oxidation of Am³⁺ → AmO₂⁺ at near-neutral pH conditions. Literature methods of AmO₂⁺ generation are generally two-step processes; i.e., Am³⁺ → AmO₂²⁺ oxidation followed by AmO₂²⁺ → AmO₂⁺ reduction. These methods for Am³⁺ → AmO₂⁺ oxidation use high temperatures (80–100 °C) and/or several reagents, causing the in situ presence of the AmO₂⁺-complex rather than the AmO₂⁺_aq ions. This not only interferes with the much-needed Am–Cm selectivity but also limits the use of AmO₂⁺_aq in any other experimental study. The single-step Am³⁺ → AmO₂⁺ oxidation in the present work using AgBiO₃ is done at 25 °C in a non-complexing medium at pH ∼4, making it a first-of-its-kind report. Am–Eu and Am–Cm separation in a single contact, with a separation factor >10⁴, was achieved using the present method, which is unprecedented among aqueous feed solutions. The AmO₂⁺ generated using the present method under non-complexing pH conditions makes it also suitable for exploring the fundamental chemistry of the higher valent americyl ion. A complexation study using the thus-generated AmO₂⁺ ion with acetate ion supports the concept.