Solvent extraction and separation of lanthanoids with mixtures of chelating extractant and 4-(2-pyridylazo)-resorcin

The solvent extraction of trivalent lanthanoids (La, Nd, Eu, Ho, and Lu) with mixtures of the chelating extractant 1-(2-thienyl)-4,4,4-trifluoro-1,3-butanedione (thenoyltrifluoro-acetone, HTTA) or 4-benzoyl-3-methyl-1-phenyl-2-pyrazolin-5-on (HP) and 4-(2-pyridylazo)-resorcin (PAR, S) in CHCl3 was studied. It was found that in the presence of 4-(2-pyridylazo)-resorcin the lanthanoids were extracted as Ln(TTA)3 ⋅ S and LnP3 ⋅ S. On the basis of the experimental data, the values of the equilibrium constants were calculated. A synergistic effect was observed for the extraction of the above-mentioned ions with the binary mixture of extractants. The separation of the lanthanoids with synergistic mixtures was higher than those obtained with HTTA or HP alone. In most cases an enhancement of the separation of metal ions was observed upon the change of the chelating extractant HP with HTTA.