1969 Volume 42 Issue 4 Pages 976-980
The effects of carboxylic acids, such as formic, chloroacetic, acetic, propionic, butyric and caproic acid, on the extraction of europium with benzoyltrifluoroacetone were studied. The extraction is enhanced by the adduct formation between metal chelates and carboxylic acids in the organic phase, while it is hindered by the formation of metal-complex ions with anions of carboxylic acids in the aqueous phase. Caproic acid acts as an organic Lewis base and shows the synergism, but formic and chloroacetic acids have a masking effect. Acetic acid, propionic acid, and butyric acid behave both as synergists in the organic phase and as masking agents in the aqueous phase. Gaproic acid forms more stable adducts than does n-hexyl alcohol, and the composition of the chelate adduct is estimated to be Eu(BFA)3·2CH3(CH2)4COOH.
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