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The results of studies of agitation leaching in combination with sorption leaching of uranium for different types of ores are reported. Sorption leaching reduces the consumption of sulfuric acid by 7–8% and reduces the processing time and makes it possible to obtain dump cakes with uranium content 0.005–0.007% and uranium concentration ≤5 mg/dm3 in the liquid phase of the discharge pulp, which corresponds to technological extraction of the uranium into anionite of at least 97%. The combined variant will make the fullest use of the capacity and potential of ion-exchange materials and permit unification of the enterprise's process scheme. [ABSTRACT FROM AUTHOR]

Abstract: The extraction of nickel and magnesium by hydrometallurgical methods is studied to develop a combined technology of sulfuric acid processing of the nickel-magnesium ores from the Aganozero deposit. The influence of the leaching parameters, namely, the consumption of sulfuric acid, the pulp density (ratio L : S), the temperature, the process time, and the milling fineness, on the extraction of the metals is studied. The optimum parameters of the kinetics, the statics, and the sorption-desorption extraction of nickel from the pulps formed after leaching the ores are determined. The use of a VPG ampholyte makes it possible to extract nickel selectively and to separate magnesium with the formation of end products of the required quality in the form of the sulfates of these metals. [ABSTRACT FROM AUTHOR]

The results of studies on the processing of carbonate ores with extraction of uranium and molybdenum by means of autoclave and atmospheric leaching and sorption extraction of valuable components using carboxyl cationionites and strongly basic anionites are presented. The most stable and highest indices for the extraction of uranium and molybdenum into solution were obtained for autoclave leaching with the following process parameters: pressure 12-14 psig, temperature ~140°C, pulp processing time 4-6 h, and initial sodium carbonate concentration 40-50 g/dm3. The degree of extraction of uranium and molybdenum into solution was ≥96%. Almost complete separation of uranium from molybdenum was obtained on carboxyl cationites without bicarbonate solutions in the pH range 6.5-7.5. An efficient technology is proposed for combined processing of silicate and carbonate ores using a unified sorption scheme making it possible to extract uranium and molybdenum separately while obtaining ammonium uranyl tricarbonate and ammonium paramolybdate. [ABSTRACT FROM AUTHOR]

The results of research on reprocessing of complex uranium ores from the Elkon deposit with recovery of uranium, gold, silver, and vanadium by methods of radiometric sorting, combining of autoclave and atmospheric leaching of ore followed by sorption and extraction recovery of valuable components, are presented. The capacity was 90 mg/g in sorption of uranium on strongly basic anionite and the uranium concentration ≤0.003 g/dm in sorption filtrates. The choice of eluent is determined by the formulation of the problem of obtaining the finished uranium product of the requisite form and quality. A fundamentally new composition of the extracting agent is proposed for direct extraction of uranium from nitrate-containing solutions. An iron-vanadium concentrate with vanadium and iron content 2.58 and 22.8%, respectively, suitable for subsequent reprocessing, was obtained. The anionite PuroGold S-992 is recommended for recovery of gold and silver. The gold and silver concentrations in the commercial desorbate were 270 and 380 mg/dm, respectively; a gold-containing concentrate was obtained. [ABSTRACT FROM AUTHOR]

The recovery of scandium from the wastes of the production of uranium, titanium, iron-vanadium, and alumina is studied. The applied acid schemes of scandium transfer to a solution followed by ion-exchange recovery and extraction concentration of scandium ensure the precipitation of crude scandium oxides containing up to 5% ScO. Scandium oxides of 99.96-99.99% purity are formed after additional refining of these crude oxides according to an extraction technology using a mixture 15% multiradical phosphine oxide or Cyanex-925 + 15% tributyl phosphate in kerosene. [ABSTRACT FROM AUTHOR]

The sequence in which uranium and phosphorus compounds are extracted from phosphate raw materials of different origin (Zaozernoe, Grachevskoe, and Melovoe deposits) is investigated. It is shown that in the case of fractional dissolution of samples from the Zaozernoe deposit the uranium is found in the solution and precipitate after acidic decomposition in the form of unrevealed uranium-containing minerals, while in the case of the Melovoe deposit the uranium and phosphorus are in solution and uranium and phosphorus deposits cannot be present in the precipitates. [ABSTRACT FROM AUTHOR]

Fine-dispersed ZnS doped with Cu was prepared using self-propagating high-temperature synthesis. In the photoluminescence excitation spectra, the blue shift of the host lattice excitation peak is observed for powder ZnS:Cu that contains nano- and mesosized (submicron) particles. The obtained spectra indicate that radiative recombination in meso-sized particles is significantly reduced as compared to micro-sized particles, which can be caused by the increase of non-radiative relaxation processes in surface states. [ABSTRACT FROM AUTHOR]

We review our recent experiments by linear optical spectroscopy in the visible spectral range on interface controlled monolayers and thin films of π-conjugated organic molecules on well-defined surfaces. In particular, cw fluorescence and fluorescence excitation spectroscopy are considered. We discuss two interesting aspects: the possibility to prepare interface controlled films with non-bulk like structures, and consequently different and possibly superior optical properties, and the use of optical spectroscopy as an analytical tool to investigate properties of interfacial organic films. [ABSTRACT FROM AUTHOR]

4(5)-Nitroimidazole in solution is stabilized as the 5-nitro isomer due to formation of hydrogen bond with an aprotic protophilic solvent. Amphiprotic medium favors displacement of the tautomeric equilibrium toward the 4-nitro isomer via formation of a solvate complex where 4-nitroimidazole acts as hydrogen bond acceptor. The observed specific solvatochromic effect in the UV spectrum of 4-nitroimidazole and related heterocyclic nitro compounds is determined by the electronic configuration of the excited π,π*-state. [ABSTRACT FROM AUTHOR]

The solvatochromism of H complexes of 5-amino-1-methyl-4-nitropyrazole and 2-nitroaniline derivatives in aprotic protophilic media was described on a quantitative level with the aid of Kamlet-Taft empirical parameters. Specific solvation affects only one of the two long-wave bands, namely that corresponding to an electronic transition involving orbital electron density transfer from the H-bound nitrogen atom. When such transfer does not occur, which is typical of the second transition, specific solvatochromic effect is either weak or absent. [ABSTRACT FROM AUTHOR]

In publishing Moscow teacher O. V. Krylova's thoughts about the new "Natural Science" [Estestvoznanie] course, it is not our purpose to cast doubt on the principle of creating integrated school subjects, and we willingly offer the pages of this journal to its advocates. However, we have to agree with the present author's opinion that whenever courses of this sort are formulated it is essential to take a balanced approach to the selection of the study material and to take account of the degree of topicality of particular kinds of knowledge to the contemporary developing world, as well as the actual possibilities that public education has at its disposal for organizing high-quality teaching of them. We invite you, dear readers, to discuss this question, which is so vital to the development of our schools. [ABSTRACT FROM AUTHOR]