MIXED-LIGAND CHELATE EXTRACTION OF TRIVALENT LANTHANIDES AND ACTINIDES WITH 3-PHENYL-4-BENZOYL-5-ISOXAZOLONE AND NEUTRAL OXO-DONORS

Mixed-ligand chelate extraction of trivalent lanthanides such as La, E u and Lu and a trivalent actinide, Am, into xylene with mixtures of 3- phenyl-4-benzoyl-5-isoxazolone (HPBI) and bis-2-ethylhexyl sulphoxide (B2EHSO) or tributylphosphate (TBP) from perchlorate solutions has bee n investigated. The results demonstrate that these trivalent metal. io ns are extracted as M(PBI)(3) with HPBI alone, in the presence of B2EH SO as M(PBI)(3) . 2 B2EHSO or in the presence of TBP as M(PBI)(3) . 2 TBP. The equilibrium constants of the above species are found to incre ase monotonically with decreasing ionic radii of these metal ions. Alt hough addition of an adduct-forming reagent to the chelate system can bring a decrease in the separation factor between Eu-Lu, it is notable that the addition of neutral ore-donor improves the separation of the Eu-Am and La-Eu pairs. The thermodynamic parameters for the extractio n of Eu(III) with HPBI alone as well as with mixtures of one of the ne utral oxo-donors in xylene have also been calculated at 298 degrees K using the temperature coefficient method.