Separation of Americium and Curium in Nitric Acid Solutions via Oxidation of Am(III) by Bismuthate and Perxenate Ions

Abstract

Studies have been carried out in order to develop new ways to separate Am and Cm in nitrate solutions. It was shown that Am(VI) produced by oxidation of Am(III) by sodium bismuthate in 0.1 and 3.0 M HNO₃ solutions is extracted with 30% tri-n-butyl phosphate solution in Isopar M diluent. Using this extractive agent in a mixture with a synergic additive of 0.1 M of trioctylphosphine oxide with 0.1 M HClO₄ makes it possible to extract into the organic phase up to 90% of the starting amount of Am with not more than 3% of Cm contained in solution. It was found that, upon introduction of Na₄XeO₆·8H₂O into a 0.1 M HNO₃ solution containing Am(III) and NaBiO₃, the solution becomes alkaline (рН ~ 10) and Am(III) is oxidized to Am(IV) to give a stable complex of composition Am(IV)·XeO₆. As a result, Am remains in solution. Sodium bismuthate present in solution is hydrolyzed to give the solid phase Bi₂O₅ by coprecipitation of hydrolyzed Cm(III). Thus, the redox separation of Am(IV) from Cm(III) in the solution formed as a result of the interaction Am(III) with a 0.1 M HNO₃ solution with sodium bismuthate and perxenate it contains is a simpler and more effective way, compared with the developed extractive method.