The Effect of the Diluent on the Extraction of Lanthanide Complexes of Macrocyclic Ionophores

Solvent extraction studies have been carried out on aqueous complexes of La(Ill), Eu(III) and Lu(III) with macrocyclic ligands DAPDA (1,7-diaza-4,10,13-tri-oxacyclopentadecane-N,N’-diacetic acid) and DACDA (1, 10-diaza-4,7,13,16-tetraoxacyclooctadecane-N,N’-diacetic acid) using TTA (thenoyltrifluoroacetone) as the extractant in chloroform and nitrobenzene. EDDA (ethylenediamine-N,N’-diacetic acid), a non-cyclic polyaminopolycarboxylic acid, was also included for comparison purposes These results, along with our earlier work in benzene medium, have been used to elucidate the nature of extracted species. It appears that nitrobenzene, a diluent of high dielectric constant, favors the extraction of ion pairs instead of the mixed complexes observed earlier using the relatively inert diluent, benzene.