Solvent extraction and separation of lanthanoids with mixtures of chelating extractant and 1-(2-pyridylazo)-2-naphthol

The solvent extraction of trivalent lanthanoids (without Pm) with mixtures of chelating extractant 1-(2-thienyl)-4,4,4-trifluoro-1,3-butanedione (thenoyltrifluoroacetone, HTTA) or 4-benzoyl-3-methyl-1-phenyl-2-pyrazolin-5-on (HP) and 1-(2-pyridylazo)-2-naphthol (PAN, S) in C6H6 has been studied. It was found that in the presence of 1-(2-pyridylazo)-2-naphthol the lanthanoids have been extracted as Ln(TTA)3S and LnP3S. On the basis of the experimental data, the values of the equilibrium constants have been calculated. The addition of PAN to the chelating extractant produces synergistic effect which is larger for the heavier lanthanoids. The separation of the lanthanoids with synergistic mixtures was higher than those obtained with HTTA or HP alone. In the most cases an enhancement of the metal ions separation was observed upon the change of the chelating extractant HP with HTTA.