Search Results
Abstract
The synergism of the crown ethers /CE/ dibenzene-18-crown-6 /DB18C6/ and 18-crown-6 /18C6/ has been investigated in the thenoyltrifluoroacetone /HTTA/ extraction of technetium from aqueous phase containing NaBH4 into benzene at room temperature. The extracted synergistic species have the general formula TcO/OH/.TTA.CE. The order of synergism was found to be 18C6>DB18C6.
Caracterisation par analyse calorimetrique differentielle des complexes entre LiAlH4 et les ethers-couronnes 12-C-4, 15-C-5, dicyclohexano-18-C-6
Comportement thermique des phases solides et de certains de leurs solvates avec le benzène
The thermal behaviour of complexes [Li+-EC](AlH4)− withEC=12-C-4, 15-C-5, DC 18-C-6 (cis-anti-cis andcis-syn-cis isomers) was investigated by Differential Scanning Calorimetry (DSC). These complexes were prepared as solids from benzene solutions. Pure EC and several solvated species [Li+-EC](AlH4)−·nC6H6 (EC=15-C-5, DC 18-C-6syn) were also studied. DSC has revealed various phenomena. Solid-solid transitions were observed before melting for [Li+-EC](AlH4)− withEC=12-C-4 and 15-C-5. They are probably explained by small molecular modifications strongly dependent on the thermal history of the sample. A glass-transition was found for the pure crown-ether DC 18-C-6anti, the complex [Li+-EC](A1H4)− withEC=DC-18-C-6anti and the two solvates mentioned above.
Abstract
Extracton, of Am3+ in benzene with 2-thenoyltrifluoroacetone (HTTA) and crown ethers (CEs) such as 15-crown-5, 18-crown-6, dicyclohexano-18-crown-6, dibenzo-18-crown-6, dicyclohexano-24-crown-8, and dibenzo-24-crown-8 was investigated. Synergistic effect by CE was observed regardless of the kind of CE examined. The extracted species was found to be Am(TTA)3(CE), and adduct formation constants between Am(TTA)3 and CE in the organic phase were determined. The sequence of constant could not be explained only by basicity of CE and the steric effect of CE should be taken into account to elucidate the adduct complex formation.
Abstract
The extraction of the trivalent lanthanides Eu, Tm and Yb(Ln) by crown ethers (CE) 12-crown-4 (12C4) and 15-crown-5 (15C5) in chloroform from perchlorate aqueous media of constant ionic strength is investigated. The effect of [H+], [CE] and [ClO
4
–
] on the respective distribution ratio (D) is elucidated. Slope analysis of these results indicated that the extracted species are of the type Ln(OH)
2
+
·ClO
4
–
(CE)2. The extraction constants obtained are in the sequence 15C5>12C4 for the CE's and Eu
Tm<Yb for the elements investigated. Based on the separation factors elucidated, Tm(III) and Yb(III) are separated from Eu(III) with high radiochemical purity; >99.5% by three (or four) successive extraction and strippings.
Abstract
The synergism of the crown ethers (CE) dicyclohexano-18-crown-6 (DC18C6), dibenzo-18-crown-6 (DB18C6) and 18-crown-6 (18C6) has been investigated in the thenoyl trifluoroacetone (HTTA) extraction of americium(III) in benzene medium from an aqueous phase of ionic strength 0.5 and pH 3.50 at room temperature (23°C). The extracted synergistic species have the general formula Am(TTA)3 · CE except for DC18C6 in which case the species Am(TTA)3·2CE was also observed at high CE concentrations. The order of synergism was found to be DC18C6>DB18C6>18C6, which is the order of the basicity of CE as indicated by their ability to extract hydrogen ions from nitric acid solutions.
