SYNERGISTIC EXTRACTION OF URANIUM(VI) BY MIXTURES OF BETA-DIKETONES AND STRUCTURALLY RELATED CROWN-ETHERS

Uranium(VI) was extracted from nitrate aqueous medium by mixtures of b eta-diketones (HX), thenoyltrifluoroacetone (HTTA)/ dibenzoylmethane ( DBzM) and crown ethers (CE) such as dicyclo-hexano-18-crown-6 (DC18C6) /dibenzo-18-crown-6 (DB18C6)/monobenzo-15-crown-5 (B15C5) in chlorofor m. The extraction constants of the chelate and of mixed species, the s ynergistic factor and the formation constant of the extracted species were evaluated. The adduct stoichiometry was found to have the general formula UO2X2.CE, irrespective of the crown ether used. It was found that no specific cavity size is required for the adduct formation. The order of synergism was found as DC18C6 > B15C5 > DB18C6, which could be explained in terms of the crown ether basicity rather than the corr espondence between the cavity size of the crown ether and the uranium( VI) crystal radii. Solid complexes of these metals with beta-diketones and crown ether have been isolated and characterized by using element al analysis, IR and NMR spectroscopic techniques.