Americium extraction method

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. 

Americium and other actinide elements may be separated from lanthanides by solvent extraction. Lithium chloride solution and an eight to nine carbon tertiary amine are used in the process. Americium is then separated from curium by the above methods. 

Weaver, B.S., Kappelmann, F.A. 1964. Talspeak A new method of separating americium and curium from lanthanides by extraction from an aqueous solution of aminopo-lyacetic acid complex with a monoacidic phosphate or phosphonate. ORNL-3559. 

Sill et al. [26] have discussed a spectrometric method for the determination of americium and other alpha-emitting nuclides, including curium and californium, in potassium fluoride-pyrosulfate extracts of soils. Sekine [27] used a-spectrometry to determine americium in soils with a chemical recovery of 60-70%. Joshi [28] and Livens et al. [29] have discussed methods for the determination of241 americium in soils. 

Sekine et al. [27] used a-spectrometry to determine plutonium (and americium) in soil. The chemical recovery of plutonium was 51-99% and averaged 81%, while for americium the recovery was 60-70%. The method is coupled with the liquid-liquid extraction stage, taking about two days less than the ion exchange method a complete analysis takes about one week. 

Furthermore, this method is not reasonably applicable to Am/Cm mixtures in which curium is present in macroconcentration. Recently (9) > we adapted the separation method developed by Mason, Bollmeier and Peppard (JO) to handle macroconcentrations of Am. This method consists of a selective extraction of americium, after its oxidation to Am(VI), by an extractant with outstanding selectivity properties, HD(DiBM)P. It can be implemented either by liquid-liquid extraction, requiring the use of centrifugal extractors (V7)> or by extraction chromatography, a simpler and less costly technique. 

Pilot plant scale testing of the extraction chromatography process is currently in progress at Rocky Flats Plant. When adequate testing of both the solvent extraction and extraction chromatography methods has been accomplished, the methods will be compared to see which has the greatest promise for recovering the americium from special MSE residues. 

Curium, berkelium, californium and einsteinium were separated from the americium samples irradiated by neutrons. For preliminary separation the anion exchange in hydrochloric acid and lithium chloride solutions was used as well as the HDEHP extraction. Mutual separation of the transamericium elements was made by using DIAION CK08Y cation exchange resin. Nuclides prepared and separation methods adopted are summarized in Table 1 (1-15). 

Studies (1, 2, 3, 4) on the separation of americium-curium from lanthanide elements indicate that both cation exchange chromatography (8, 9) and the Talspeak solvent extraction process (U), 11) are promising methods. Only the most recent work at Oak Ridge National Laboratory is reported in this paper. Potential chemical processes for americium-curium removal and evaluations of their feasibility have been reported previously (U 2, 3, 4). The most recent experimental work carried out includes the following ... 

The americium is then stripped from the organic with water (five to seven contacts) using an A/0 0.2. The americium in the strip solution is precipitated with oxalic acid, and the americium oxalate is calcined to Am02. In the lab scale extraction chromatography method, the DHDECMP-impregnated Amberlite XAD-4 was loaded into a column 1.8 cm dia. x 23.5 cm and conditioned with 7M HNOj. The americium feed was fed to the column at 1.5 ml/min until a total of 300 ml had been fed. The column was washed with 200 ml of 7M HNO3 at 1.7 ml/min, then eluted with deionized water until elution was complete (determined radiometrically). Five to seven 50 ml fractions were required for elution. Samples were submitted for analysis. 

Bhattacharyya, A., Mohapatra, P. K., Roy, A., Gadly, T., Ghosh, V. K., and Manchanda, V. K. 2009. Ethyl-bis-triazinylpyridine (Et-BTP) for the separation of Americium(lll) from trivalent lanthanides using solvent extraction and supported liquid membrane methods. Hydrometallurgy 99 18-24. 

Weaver, B. and Kappelmann, F. A. (1964) Talspeak A New Method of Separating Americium and Curium from the Lanthanides by Extraction from an Aqueous Solution... 

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