Precipitation methods americium separation

Mullins and Leary [29] patented a method of separating americium from plutonium which involves bubbling a mixture of oxygen and argon gas into a molten salt containing both elements. Plutonium precipitates as PuOj, whereas americium stays in solution. 

Americium may be separated from other elements, particularly from the lanthanides or other actinide elements, by techniques involving oxidation, ion exchange and solvent extraction. One oxidation method involves precipitation of the metal in its trivalent state as oxalate (controlled precipitation). Alternatively, it may be separated by precipitating out lanthanide elements as fluorosilicates leaving americium in the solution. Americium may also he oxidized from trivalent to pentavalent state by hypochlorite in potassium carbonate solution. The product potassium americium (V) carbonate precipitates out. Curium and rare earth metals remain in the solution. An alternative approach is to oxidize Am3+ to Am022+ in dilute acid using peroxydisulfate. Am02 is soluble in fluoride solution, while trivalent curium and lanthanides are insoluble. 

These two techniques are routinely used for the Am/Cm separations that we perform. However, they both have disadvantages. In the case of the precipitation of the double carbonate, the relatively high solubility of americium in solution (50 to 100 mg/L) requires reprocessing of the supernatant solution from the precipitation step which must be diluted considerably to avoid the precipitation of KN0 after acidification by HN0. For method (b), failure to oxidize the americium results in a loss to the CmF- precipitate. 

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