Interlayer confinement mediated oxidation of americium by sodium bismuthate and stability of its higher redox states in acidic solution.

Mutual separation of trans -plutonium actinides (Ans) from lanthanides (Lns) or adjacent Ans is challenging as they exhibit great chemical similarity. Selective Am oxidation-based Am-Lns or Am-Cm separation strategies give very high separation factors. There exist several reports on different aspects of Am 3+ oxidation by NaBiO 3 · x H 2 O ( x = 2-3), which suggests that the oxidation mechanism is still not well understood. We, therefore, carefully performed several experiments taking advantage of the difference in the redox chemistry of Eu 3+ and Am 3+ . The ion exchange of Eu 3+ with the interlayer Na + in NaBiO 3 was confirmed by an ionic strength variation experiment. The shift in the 001 peak of NaBiO 3 in XRD and the appearance of peaks corresponding to the trivalent Ln ions in XRF after Ln 3+ loading give direct evidence for Na + exchange with Ln 3+ . The stability of the higher oxidation state of Am was monitored spectrophotometrically. The experimental investigations also suggested the role of Am 3+ → AmO 2 2+ transformation in NaBiO 3 · x H 2 O ( x = 2-3) dissolution even at pH ∼ 1, which otherwise is difficult to achieve even with >1 M HNO 3 . The role of colloidal NaBiO 3 particles and dissolved BiO 3 - in controlling or stabilizing different oxidation states of Am was also discussed.