Spectrophotometric study of uranium(VI) chelate formation with beta-diketones and tributyl phosphate in aqueous, nona(oxyethylene) dodecyl ether solution.
The distribution ratio of uranium(VI) with 2-thenoyltrifluoroacetone, 2-furoyltrifluoroacetone and benzoyltrifluoroacetone in the presence and absence of tributyl phosphate between micellar and bulk phases in nona(oxyethylene) dodecyl ether solution was measured spectrophotometrically as a function of hydrogen-ion concentration. The thermodynamic constants for these reactions were evaluated from the variation of the equilibrium constants as a function of temperature. The entropy change contributes to the synergistic reaction.
Temperature effects in synergistic solvent extraction
Abstract The extraction of Eu(III) and Tm(III) has been studied in mixed systems of TTA + TBP and TTA + AA (TTA = 2-thenoyltrifluoroacetone; TBP = tributylphosphate; AA = acetylacetone). The formation constants of Eu(TTA) 3 , Eu(TTA) 3 (TBP) 2 , Eu(TTA) 3 ( AA), Tm(TTA) 3 , Tm(TTA) 3 (TBP) and Tm(TTA) 3 (AA) were measured as a function of temperature to obtain free energy, enthalpy and entropy changes. The thermodynamic parameters support a mechanism for synergism in which the coordination number of the lanthanide ion expands when Ln(TTA) 3 forms Ln(TTA) 3 (( S ) n where S is TBP or AA.
Regularities of extraction of uranyl thenoyltrifluoroacetonate into a number of solvents
The extraction equilibria were investigated of the thenoyltrifluoroacetone (TTA) chelate of uranyl ion between aqueous perchlorate medium and thirteen organic solvents. The extracted species was shown to be UO2A2. The solubility parameter of the chelate was estimated from the partition data and it was confirmed that the relationship lgPM=n lgPHA+const. holds for the present system. When the extraction constant (Kex) is considered in relation to the distribution coefficients, theKex values are expected to be constant under certain conditions for all of the solvents; the lgKex values were found to be constant (lgKex=−2.85±0.17).