Kinetics of Solvent Extraction of Lanthanide Complexes of Macrocyclic Diaminodicarboxylic Acids

Studies of the kinetics of extraction of La(III), Eu(III), and Lu(III) complexes of 1,7-diaza-4,10,13-trioxacyclopentadecane-N,N′-diacetic acid (DAPDA) and l,10-diaza-4,7,13,16-tetraoxacyclooctadecane-N,N′-diacetic acid (DACDA) have been carried out at pH 5.5 and 7.5. Thenoyltrifluoroacetone (TTA) was employed as the extractant in chloroform. The rates of extraction were found to be influenced by the nature of the extracted species. For the binary species, Ln(TTA),, the rates were governed by the dissociation rates of their macrocyclic complexes in the aqueous phase and were relatively slow. For some cases where extractions involved predominantly ternary species, Ln(DAPDA/ DACDA)TTA, the rates were relatively fast and independent of the aqueous macrocyclic complex dissociation rates. The significance of the rates of solvent extraction were discussed.