Extraction of U (VI) and Am (III) was studied with a synergic combination of a chelating extractant, thenoyltrifluoroacetone (TTA) and a neutral donor, tri-
n-octyl phosphine oxide (TOPO). The synergic extraction constants
Kez, s in single solvents are related to the solubility parameter of the organic solvent δ
org by a simple correlation; log
Kex, s=
2Bδ
org+constant, where
B is a negative constant depending on the type of synergic adduct.
The kind of solvent and the mixing ratio of solvents gave no effect on the type of adduct complex. The extracted species were found to be UO
2(TTA)
22·TOPO and Am (TTA)
2·2TOPO. The synergic extraction constants decreased with increasing content of solvents of large solubility parameters. Dilution with these solvents, particularly with chloroform, was favorable for back extraction. A difference in solvent effect on synergism of different adducts results in an effective mutual separation. Both the adduct complexes of U and Am were extracted into the hexane solution bringing about large synergism, and then only Am could be stripped from the organic phase after dilution with chloroform.
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