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.
Metal complexes in solvent extraction studies—III Preparation and investigation of binary and ternary complexes
Abstract Some ternary complexes of the type M(chelate) 2 S x [M = UO 2 2+ , Cu 2+ , Zn 2+ , Ni 2+ , Co 2+ , chelate = TTA (thenoyltrifluoroacetone anion), S = TBP (tri-n-butyl phosphate), TBEP (tri-n-butoxyethyl phosphate, TOPO (tri-n-octyl phosphine oxide), 4-me-py (4-methyl pyridine), TPPO (tri-phenyl-phosphine oxide)] have been prepared and investigated. Preliminary work has also been carried out with HFacac (hexafluoroacetylacetone anion), TFacac (trifluoroacetylacetone anion) and acac (acetylacetone anion) as chelates. The compounds Zn(HFacac) 2 · x H 2 O ( x = 1 and 2), Zn-(HFacac) 2 (TOPO) 2 , Cu(HFacac) 2 TOPO, Co(acac) 2 (4-me-py) 2 , UO 2 (acac) 2 ·4-me-py and UO 2 (acac) 2 (TPPO) 3 have also been isolated. Solvent extraction studies show that the synergistic extraction of 65 Zn depends upon the nature of the chelate and of S. It is suggested that the phenomenon of synergism involves both the stability of M(chelate) 2 · x H 2 O and M(chelate) 2 S x and further, that the bonding of S, which is directly to the metal, is weak and comparable to solvation or adduct formation.
Synergism in the solvent extraction of di, tri and tetravalent metal ions—III: Antisynergism with thenoyl trifluoracetone
Abstract Greatly enhanced extraction (synergism) of di, tri and tetravalent cations from aqueous solution has previously been reported for the system H 2 O/M n + /HTTA/S/diluent, where S is a neutral organophosphorus ester and HTTA is thenoyl trifluoracetone. Examples are now given where S contains no phosphorus and is an amide, alcohol or ketone. Complete destruction of this greatly enhanced extraction by addition of excess S whether the neutral additive is a phosphorus ester, an amide, alcohol or ketone is demonstrated. These antisynergic effects are shown to be greater than, but the same type as, the effects due to some so called inert diluents. This phenomenon of antisynergism is shown to be connected with the water contents of the organic phase and the destruction of the anhydrous synergic species M(TTA) x S y . The HTTA thermodynamic activity is lowered and water probably enters the complex. Absorptiometric measurements demonstrate three different spectra for HTTA/TBP in non-aqueous solution (a) the enolate form in dry TBP, probably hydrogen bonded to the TBP (b) the normal enol form in hexane solution in the presence or absence of low concentrations of TBP and water and (c) the ketohydrate form in water equilibrated TBP. UO 2 (TTA) 2 or Th(TTA) 4 in dry TBP have the HTTA enolate spectra whereas in wet TBP the metal/TTA enol spectra obtains, evidence that water helps to destroy the anhydrous synergic species, causing antisynergism to occur.