Home – Home – Jornals – Chemistry for Sustainable Development 2009 number 4

Known laboratory and industrial methods of obtaining guanamines (6-alkyl- or aryl-substituted 2,4-diamino-1,3,5-triazines) based on modification of substituents in the triazine ring and synthesis from acyclic precursors are described. It is shown that at present the most convenient method of obtaining guanidines is the reaction of dicyandiamide with nitriles in the presence of a strong base, with high-boiling alcohols as solvents. The reaction conditions are considered in detail, the data on its kinetics and mechanism are presented. The conditions of the industrial implementation of this reaction allowing one to develop an up-to-date low-waste technology of obtaining high-quality guanamines are described.

Dynamics of electrolytic recovery of copper from the sulphuric acid electrolyte on carbon fibrous electrodes with constant initial conductivity over the electrode thickness, overall current density, rate and direction of solution feed to the electrode are investigated in application to the technology of copper recovery from the trapping tank of an automatic line of galvanic works.

Sorption properties of bentonitic clay from the Kamalino deposit (Krasnoyarsk Region) are investigated for the purpose of its possible use for the purification of waste water from sulphide-containing tailing dumps from heavy metal ions. For copper (II) as an example, the effect of pH, sorbate to sorbent ratio and an increase in the concentration of the sorbate on metal redistribution from the model solution into the solid phase is investigated. On the basis of the examination of water extracts from the clinker substance of the Belovo zinc plant (Kemerovo Region) and its drainage waste water, it is established that this object serves as a source of the acid mine drainage water of the most unfavourable type (negligible iron content and high content of heavy metals and sulphate sulphur). It is shown that efficient results on the purification of waste water from tailing dumps of the Belovo zinc plant may be obtained using purification in two stages: at first, with calcite, then by means of the interaction with clay sorbent.

Dynamics of transition modes in the reaction of steam conversion of СО on Ce_{0.5 - х}Zr_{0.5 -х}La_2хO₂ (х = 0, 0.1) and platinum catalysts on this basis at 650 ^оC is investigated. Numerical modeling of the response curves showed that all the transformations on the support run within the oxidation-reduction mechanism. At the catalyst under the steady conditions, the major contribution into the activity is made by the transformations according to the association mechanism. The dynamics of transient modes is determined by the oxidation-reduction mechanism.

Content of vitally necessary microelements (Fe, Mn, Zn, Cu, Mo, Co, Cr) in some medicinal herbs growing in the steppe arid, meadow landscapes with insufficient and normal wetting, and in meadow-bog landscapes on the soil of different types in West Transbaikalia was investigated.  The species and ecological specificity of the accumulation of microelements in the herbs was determined. Different levels of microelement content in herbs were established; the plant concentrating Fe, Mn, Zn, Cr were determined. Molybdenum, copper and zinc were ascribed to the elements of intensive absorption from soil, manganese and cobalt - of medium absorption, while iron and chromium were ascribed to the elements of weak absorption.

Ion-exchange sorption of cerium (III) ions from aqueous solutions of cerium sulphate by natural morednite-containing tufa was studied under the static conditions. Quantitative extraction of cerium from diluted (<0.003 mol/l) solutions was established. It was stated that an increase in the solution concentration causes a decrease in the sorption capacity of tufa. Isotherms of absorption of cerium ions were plotted; the kinetic parameters of the sorption process were determined.

Results of laboratory investigation of thermal decomposition of technical-grade calcium carbonate (phosphochalk) obtained by conversion of phosphogypsum with sodium carbonate and calcium leaching by ammonium chloride into solution are presented. It is established that phosphochalk completely decomposes to form aO at a temperature of 900 ^oC. As a result of leaching for the molar ratio NH₄Cl : CaO_акт > 2.1 almost the whole CaO_act passes into solution. Carbonization of the resulting CaCl₂ solution allows one to obtain high-quality calcium carbonate. Rare-earth elements and strontium get concentrated during CaO_act leaching in the insoluble residue; their content increases to 4-5 and 10-11 %, respectively. Therefore, the insoluble residue may be considered as a raw material to obtain the compounds of REE and strontium.

Physicochemical properties of lignohumic acids, colloid properties of the aqueous solutions of their salt forms (surface tension, limiting wetting angle, viscosity) were investigated. The structure of lignohumic acids was determined using IR and EPR spectroscopy. A comparison between the properties of lignohumic acids and humic acids of peat was carried out. It was shown that lignohumic acids are close in their properties to humic acids of peat.

Effect of mechanochemical activation on the properties of indometacin is investigated. The dynamics of indometacin molecules is demonstrated by means of EPR; possible nature of this process is assumed. Investigation of indometacin mechanochromism in mixtures with different polymers showed that the appearance of colouring is independent of the occurrence of indometacin interaction with auxiliary susbtances but colouring is unstable in the absence of the interaction.

Under the conditions of the forest-steppe zone of West Siberia, the dynamics of accumulation of saccharides, starch, saponins, ascorbic acid, pectins, protopectins, catechines, tannins in the bulbs of introduced species Scilla sibirica and Ornithogalum ponticum was established for the first time. The component composition of the bulbs of these taxons was described.

Catalytic dehydrochlorination of 1,2-dichloroethane on a series of two-component silicate catalysts with regularly changing acid-base properties (Al₂O₃/SiO₂, Ga₂O₃/SiO₂, ZiO₂/SiO₂, BeO/SiO₂, Y₂O₃/SiO₂) and on oxides (γ-Al₂O₃, MgO) is investigated in a flow set-up at a temperature within the range 250-450 ^оC. It is established that the degree of 1,2-dichloroethane transformation into vinyl chloride is determined by the strength of Lewis acid centres. It is shown that catalyst deactivation is due to the formation of 1,3-dichlorobutene-2.

Cadmium binding with humic acids (HA) extracted from a sample of a lake bottom sediment is investigated as the dependence on the acidity of the medium in the system (within the pH range 3-10) and on the concentration of cadmium ions (5, 10 and 50 μmol/l). The ion-exchange separation of unbound cadmium ions and its complexes with HA was carried out by means of ion exchange on the sulphocationite followed by analysis by means of the flame atomic absorption spectrometry. Cadmium binding in the system containing kaolin and HA is studied within pH range 3-10. A comparative analysis of the overall cadmium binding in the systems containing kaolin and HA separately and in the system containing them both was carried out for other conditions being the same. The fraction of the metal bound with HA in solution, in precipitate, and on the surface of kaolin was taken into account. It was shown that the additivity of the systems (a decrease in the concentration of the free metal in the ternary system is equal to the sum of the values of concentration decrease in binary systems under the same conditions) is observed within the range pH 4.6-5.8. In other cases, cadmium binding in the ternary system will be lower than in the sum of binary systems: at first, due to HA deactivation due to its adsorption on kaolin surface (in the acid pH region), then due to blocking of the adsorption centres of kaolin (in the neutral and alkaline pH regions).

Effect of preliminary mechanical activation of ground vulcanizates on the elastic-strength characteristics and the structure of composites was investigated. Powdered rubber was obtained by grinding various model elastomer compositions and real industrial waste material from the production of rubber goods.

It is demonstrated that mechanical activation of a mixture of Mg(OH)₂, Al(OH)₃ and Na₂CO₃ in the planetary activator AGO-2 followed by water treatment of activation products leads to the formation of the Mg-Al layered double hydroxide. Single-phase double Mg-Al hydroxide is formed if the initial Mg(OH)₂/Al(OH)₃ molar ratio is within the range 1.5/1-4/1. Both carbonate and hydrocarbonate anions are present in the interlayer space. The synthesized samples of the double hydroxide were characterized by means of XPA, TG, DTA and chemical analysis.