Mixed-ligand chelate extraction of thorium(IV) and uranium(VI) with thenoyltrifluroacetone and various imidazoles

The synergistic extraction of thorium(IV) and uranium(VI) has been studied using mixtures of thenoyltrifluoroacetone (Htta) and various imidazoles suc h as imidazole (Imz), 2-methylimidazole (2-Meimz), benzimidazole (Bimz) or 2-pyridylbenzimidazole (2-Pybimz). The extraction data have been analysed b y both graphical and theoretical methods by taking into account chemical ma ss action principles. The results demonstrate that these metal ions are ext racted into chloroform as Th(tta)(4) and UO2(tta)(2) with Htta alone and as Th(tta)(4) . nS and UO2(tta)(2) . nS in the presence of imidazoles (where n = 1 and 2 for thorium(IV) and n = 1 for uranium(VI); S represents imidazo le). The equilibrium constants of the above extracted complexes have been d educed by non-linear regression analysis. The addition of an imidazole to t he metal chelate system enhances the extraction efficiency of these metal i ons. The complexation strength of these metal ions with various imidazoles follows the order: Imz > 2-Meimz > Bimz > 2-Pybimz.