No abstract available

[en] Full text of publication follows. To improve the recycling of nuclear fuel (as well as the reducing of the volume and the toxicity of ultimate waste), different actinide separations have been considered. Specific families of molecules were selected considering several criteria; among them the performance in terms of chemical affinity and selectivity towards the actinide target was important. The design and/or the optimization of new ligands could be improved with a deep understanding of actinides distribution and of the selectivity. N, N-dialkyl-amides RR'N-C(O)-R'' belong to a classical family of extractants which have been proposed some years ago to selectively separate uranium(VI) and plutonium(IV). The influence of the alkyl groups R, R' and R'' on the extraction and physico-chemical properties has already been discussed. But the relation between a macroscopic behavior of a solvent extraction system and the molecular contributions is difficult to obtain with high solute concentrations. In order to increase the knowledge in this field, a large number of investigations have been applied on the same extraction systems (3 reference dialkyl-amides): -) Thermodynamic data (free energy Δ_extG⁰, enthalpy Δ_extH⁰ and entropy Δ_extS⁰) were acquired by the classical Van't Hoff method and by direct calorimetry to provide the enthalpies of extraction and also specific heats; -) Dedicated methods like electro-spray ionization mass spectrometry analysis and X-ray diffraction on single crystals provide information about the stoichiometry of the extracted species; -) Spectroscopic investigations with UV-visible absorption, Fourier transform infrared and XAS experiments combined with theoretical calculations probed the actinide coordination in the inner sphere. The results obtained will be discussed to identify the origin of the different affinities between ligands and the difference of selectivity between cations. (authors)

[en] It is pointed out that hydrocarbons are widely used as diluents in solvent extraction processes involving a wide variety of metals and extracting agents of both the chelating and non-chelating types, and that the introduction of hydroxy oxime chelating type extractants and their application to large scale solvent extraction processes for metals has led hydrocarbon solvent manufacturers to consider the use of special purpose diluents. The manufacture, properties and uses of such diluents are reviewed. Sections are included on treatments to remove impurities, solvent blending, selectivity, kinetics of extraction and stripping, etc. Research and lines for future investigation are indicated. (U.K.)

[en] Quantitative extraction of uranium(VI) is observed from 0.2M HCl by 5% (v/v) Cyanex 301. The extraction decrease with increasing acid concentration. Mixtures of Cyanex 301 with tri-n-butyl phosphate (TBP), didecyl sulfoxide (DDSO) and Alamine 308 result in significant synergism in the extraction process, where a species of the type UO₂R₂ x L is proposed to be extracted to be extracted [RH = Cyanex 301 and L = TBP, DDSO or Alamine 308G. Significant extraction of uranium(VI) by 5% (v/v) Alamine 308 is observed at and above 2M HCl, which increases with further increase in acidity attaining a maximum at ∼ 6M, after a which a slight decrease in extraction is observed. Mixtures of Alamine 308 with TBP or DDSO result in a synergism, where a species of the type (R₃^'NH)₂UO₂Cl₄ x L is extracted. [R₃^'N Alamine 308, L = TBP or DDSO]. Mixtures of Alamine 308 and Cyanex 301 at ≥ 2M HCl result in a profound antagonism in the extraction of uranium(VI). (author) 17 refs.; 5 figs.; 2 tabs

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[en] The extracting agent comprises an organophosphonic acid or phosphinic acid but instead of paraffinic hydrocarbons as diluent halogenated hydrocarbons or carboxylic acid are claimed to improve reextraction of rare earths from the organic phase

[en] TECHXTRACT is a proprietary chemical decontamination technology employing as many as 25 different chemical components in three separate formulations that are used in sequence to extract contaminants

[en] Ionic liquids are alternative reaction media of increasing interest and are regarded as an eco-friendly alternatives, of potential use in place of the volatile organic solvents typically used in current chemical processing methods. They are emerging as the smart and excellent solvents, which are made of positive and negative ions that they are liquids near room temperature. The nucleophilic substitution reaction is one of the important method for inserting functional groups into a carbon skeleton. Many nucleophilic substitution reactions have been found with enhanced reactivity and selectivity in ionic liquid. In this review, some recent interesting results of nucleophilic substitution reactions such as hydroxylations, ether cleavages, carbon-X (X = carbon, oxygen, nitrogen, fluorine) bond forming reactions, and ring opening of epoxides in ionic liquids are discussed

[en] Single-channel coaxial segments were used for the introduction of an aqueous or octan-1-ol solution of an organic substance directly into a continuous flow of the other solvent. The analytical signal was measured simultaneously on both aqueous and organic phase segments by an 'on-tube' fast-reading spectrophotometric detector (ca. 3 ms time resolution) and treated mathematically. The octan-1-ol-water phase signal ratio corresponds to the partition coefficient of the organic substances. The applicability of the method is demonstrated by the determination of partition coefficients of phenol, citric acid, acetylsalicylic acid and sodium salicylate. (author). 8 refs.; 3 figs.; 1 tab

No abstract available