Studies of Actinium(III) in Various Solutions. II. Distribution Behavior of Lanthanum(III) and Actinium(III) in Some Chelate Extraction Systems

Abstract

Distribution behavior of lanthanum(III) and actinium(III) at tracer concentrations was studied in metal chelate extraction systems where the organic phase was chloroform containing dibutylphosphate, thenoyltrifluoroacetone (TTA), β-isopropyltropolone or 5,7-dichloroxine. The separation factors for this pair of ions by extraction with these four chelating ligands were determined. The distribution behavior was also studied in the adduct chelate extraction systems where the organic phase was carbon tetrachloride containing mixed ligands, TTA-tributylphosphate (TBP) or TTA-methyl isobutyl ketone (MIBK). The adduct formation constants for actinium-(III)-tris-TTA chelate with these neutral ligands were determined. Results were compared with previous results on the distribution behavior of other trivalent actinide and lanthanide ions in these systems. It was concluded that the separation of lanthanum-actinium was somewhat different from the separation of europium-americium in the same chelate extraction systems. The stabilities of the first adducts with TBP or MIBK of actinium TTA chelate were smaller than those of americium TTA chelate, but the stabilities of the second adducts showed just the reverse order. This tendency in adduct formation is the same as that observed among the lanthanum and europium adduct TTA chelates in previous work. Finally, the use of TTA-TBP mixture was recommended for the extraction of lanthanum(III) or actinium(III) at tracer concentrations based on the fact that the use of these mixed ligands resulted in much better recovery of material and better reproducibility of results than a single chelating ligand.