Home – Home – Jornals – Chemistry for Sustainable Development 2012 number 3

Known laboratory-scale and industrial methods are reviewed therein concerning the production of one of the most important vulcanization accelerators such as kaptax (2-mercaptobenzothiazol) those are based on modifying the substituents in the thiazol ring and synthesizing from acyclic precursors. The latter include also the main industrial method of obtaining kaptax based on the reaction between aniline, sulphur and carbon disulphide dangerous from the environmental point of view. Potentialities are demonstrated concerning the development of methods for producing kaptax without using carbon disulphide, which would significantly improve the environment safety of the process.

Results of the investigations carried out by the authors during the past five years in the area of chemical transformation of cytisine alkaloid are presented. A number of new polyfunctional derivatives of cytisine alkaloid containing pharmacone groups including heterocyclic fragments were obtained. The composition and structure of the synthesized compounds were confirmed by means of the data of mass spectrometry, ¹Н NMR spectroscopy and X-ray structural analysis. Some features of the spatial structure of cytisine were established. The data obtained in the investigation of the biological activity of the synthesized derivatives are presented.

Main catalytic processes and fuel types are described inherent in the production of hydrogen for low-temperature fuel cells. Different types of solid membranes for extracting hydrogen from gas mixtures are considered. Descriptions of new membrane reactors are presented and the prospects for their use in hydrogen energy engineering are assessed.

Experimental data on water-assisted migration of uranium and microelements that are satellites of gold, from the dumps formed during exploration works in 1960–1970 at the territory of gold and uranium deposits of the Elkon horst (Yakutia) are presented. Investigations were carried out using a complex of methods including X-ray fluorescence analysis with the synchrotron radiation, semiconductor high-precision gamma spectrometry, scintillation gamma spectrometry, instrumental neutron activation analysis etc. It was established that the excavation dumps are the objects of increased ecological risk.

A method is proposed for making a composite material based on a molecular mixture of polytetrafluoroethylene and SiO₂ via absorbing the on thermal decomposition products of ammonium hexafluorosilicate and polytetrafluoroethylene in ammonia water. Using XRD diffraction analysis, it was evidenced that there is of SiO₂ molecular distribution observed in the composite structure. An influence of the compound introduced upon the yield of fluorosilicon composite output from the gas phase was studied

Assessing the activity of monoamine oxidase enzyme was performed for the reactions of serotonin, tryptamine and benzylamine deamination in different groups of animals according the ratio between the maximum deamination rate (w_max) and the Michaelis constant (KM). For the representatives of mammalian species studied the ratio of w_max/KM ranges within 1.0–3.6, for birds this range is wider amounting to 0.4–5.0, for fish this value ranges within 0.3–1.8. It was demonstrated that increasing the concentrations of substrates (up to 10^–2 mol/L) or temperature (up to 42 °С) promotes the enzyme activation.

Kinetic laws inherent in the sorption of praseodymium (III) ions from sulphate solutions on mordenite containing tuff. Kinetic parameters for the sorption process were determined, and constructed absorption isotherms for praseodymium ions were obtained. It has been established that the rate-determining stage is presented both by external and internal diffusion. From dilute solutions (<0.002 mol/L) praseodymium can be extracted to a complete extent.

The kinetics of mullitization of kyanite samples, both initial and mechanically activated in high-energy grinding devices within temperature range 1273–1573 K was investigated. It was shown that the kinetics of kyanite mullitization formally corresponds to the equation of monomolecular decomposition. The activation energy of this transformation is (630±10) kJ/mol. It was established that mechanical activation of kyanite accelerates mullitization processes during subsequent thermal treatment. The yield of mullite per unit surface area is almost two times higher for mechanically activated sample than for non-activated one. Possible mechanism of mullitization process and technological aspects of the implementation of this process in industry are discussed.

Using dynamic light scattering technique, studying the destruction process were performed for the agglomerates of electro-explosion aluminium nitride nanopowder composition Al/AlN under ultrasonic dispersing in isopropyl alcohol. The average size of the initial agglomerates amounts to ~5.4 μm. It has been demonstrated that under the conditions of dispersing under investigation the initial agglomerates are disintegrated to produce a particle size of about 0.5 μm. No destruction resulting in primary particles of 40–80 nm in size is observed. It is demonstrated that the deagglomeration exerts a considerable effect upon the chemical reactivity of the aluminium nitride nanopowder composition in the reaction with water. It has been established that the size of the precursor particles exerts a substantial effect on the formation of a modifying nanostructured porous coating on polymeric fibres and on adsorption properties of the fibrous sorbent based the mentioned coating.

A process of purifying complex multicomponent technological solutions with the use of a combined sorption-and-electrochemical method was studied. By the example of processing the technological solutions from the Belovo Zinc Plant and from the sulphuric acid workshop of the Ural Mining and Processing Company, a potentiality of combined using the adsorption and electrochemical stages for efficient extracting of HMI and arsenic up to attaining required MPC standards for discharging the solutions into a sewage system was demonstrated. This allows reducing to a significant extent the hazard inherent in the wastewaters and technological solutions, improving the environmental situation around the enterprises and reducing the metal loss.

With the use of X-ray diffraction, SEM, XFA, IR spectroscopy, and a Cryogenic High Field Measurement System we studied the composition, structure, properties of powders of iron ore concentrate from the Mikhailovskiy OMPE with a view to its use as a magnetic adsorbent for removing oil from the surface of water. It was demonstrated that the specific surface of the concentrate is equal to 1.5 m²/cm³, the concentrate exhibiting hydrophobic properties due to the formation of carbon on the surface thereof after the pyrolysis of the flotation reagent and starch resulting from drying at 800 °С. The specific magnetic saturability of the concentrate is 2.3 times higher than the specific magnetic saturability of pure magnetite, which could be caused by the penetration of iron atoms from the equipment into the interior of the concentrate particles (1 μm from the surface) as a result of the procedures of extraction, grinding, of dry and wet magnetic separation and flotation in the course of obtaining the concentrate. It was noted that the oil exhibits weak magnetic properties due to the presence of natural and man-made magnetic substances therein. After adding 1–5 % of the concentrate the specific magnetic saturability of hydrocarbons reaches 0.6–3 A · m²/kg. Ways to use the concentrate are under discussion.

Two variants are presented for the hydrometallurgical extraction of rhenium from the solutions of complicated composition, obtained via recycling the wastes of multicomponent refractory alloy ZhS-32. The applying of both schemes results in the formation of AR-0 grade NH₄ReO₄. The yield of the metal amounts to 99.2 % from the initial metal content in the alloy. The techniques used allow performing a single stage separation of the rhenium from impurity metals with eliminating the channels of the irretrievable loss thereof.

Chemical composition of assimilating organs of Pinus Sylvestris and Betula pubescens in the zone affected by the GMK Pechenganikel JSC situated in the northwest of the Murmansk Region near the borders of Finland, Norway and Russia was studied. Anomalously high concentrations of copper and nickel in the leaves (needles) of trees under the conditions of technogenic pollution were revealed. Insufficient provision of pine needles with nutrition elements – phosphorus and potassium – was discovered. Higher concentrations of copper, nickel and sulphur in comparison with their concentrations in pine needles were detected.

Effect of mechanical activation of the powder mixture 3Fe + Al on the structure of mechanocomposites and their evolution during self-propagating high-temperature synthesis was investigated. It was shown that substantial decrease of the temperatures of heat evolution start typical for thermal explosion and the critical temperature of thermal explosion of preliminarily activated mixtures is connected with the presence of regions with fine layered structure in agglomerates, while the heterophase character of synthesis products is due to relatively low maximal synthesis temperature. It was established that mechanical activation of the systems Fe–Al leads to a substantial increase in the catalytic activity of Fe₃Al intermetallide during methane conversion into synthesis gas, and also to an increase in the conversion degree of CH₄ and CO₂ to 93 and 91 %, respectively. In the case of the sample without mechanical activation, these parameters are only 15 and 53 % for CH₄ and CO₂, respectively.