Home – Home – Jornals – Chemistry for Sustainable Development 2005 number 4

The work is focused on the most developed hydrometallurgical methods of lead and its compounds processing, using sulphuric and hydrochloric acids. Major drawbacks of these techniques, that hamper industrial use, are shown. In particular, the barriers caused by the low solubilities of lead sulphate and chloride. The usefulness of hydrometallurgical flowsheets involving nitric acid for lead-containing raw materials processing was shown. The advantages include: high degree of metal extraction (up to 96-99 %), almost complete reagents regeneration. Under the testing conditions the methods had demonstrated superior to pyrometallurgical processes ecological safety.

Atmospheric pollution of ecosystems in the region of the Neryungri fuel and energy complex (NFEC) was considered. Mathematical modeling of the processes of aerosol transport of dust, SO₂, NO₂ was carried out by means of the formulation of the direct and inverse problems. An adequate model, in which the regions with different degree of atmospheric pollution were distinguished, was chosen on the basis of comparing the calculated dust content of the snow cover with the data experimentally measured for 22 sites. A correlation analysis of changes in the chemical composition of the upper horizons of top-soil and larch tissues (Larix cajanderi Mayr.) depending on the degree of atmospheric dust content was carried out. It was revealed that the concentrations of heavy metals (Fe, V, Ni, Cu, Zn, Ga, Mo, Pb) in larch tissues increase with an increase in atmospheric pollution. The correlation coefficient for needle nodes is not lower than 0.8 while no such correlation is observed for soil. An inverse correlation was established for biophilic element Mn: the higher is environmental pollution; the lower is its content in larch tissues. The accumulation of heavy metals in the organs if larch increases in the row: young sprouts-needles-buds.

Structural parameters of humic acids of oxidized coal from the deposits of Buryatia were determined using quantitative ¹³C NMR spectroscopy. Estimation of physiological activity of humic acids of oxidized coal was carried out under the conditions of agrotechnical tests. An interconnection between the characteristics of physiological activity and structural parameter Ô of humic acids was discovered; it was assumed in this connection that ¹³C NMR spectroscopy would be a promising tool to predict biostimulant characteristics of humic acids.

The distribution and composition of low-molecular nitrogen-containing components in petroleum from the Lower and Middle Jurassic complex of West Siberia were investigated. The dependence of the quantitative content and qualitative composition of hetero-organic compounds of nitrogen on the geological-geochemical bedding conditions was revealed. It was established that the group and individual composition of nitrogen-containing compounds of the Lower and Middle Jurassic petroleum is typical also for petroleum from the Cretaceous and Upper Jurassic deposits of the West Siberian oil-and-gas province. No evident differences in the distribution of predominant types of low-molecular nitrogen-containing compounds were revealed in the investigated kinds of petroleum.

Hypergene processes in the waste products of concentration of copper and nickel ores (tailing dumps in the Afrikanda settlement, Murmansk Region) were investigated by means of physicochemical modelling using the Selektor software. New formations in the solid phase are represented by goethite (over sulphides) and three-layered layered silicates. The appearance of gypsum is observed in the case of substantial interaction. The concentration of nickel in the pore fluid exceeds the MPC even under a 0.01 % change in volume. The results indicate that the concentrations of heavy metals are rather high in pore fluid, though its pH is higher than 8 as a mean in all the samples, which brings real danger to the environment.

To develop a porous structure of anthracites of Donetsk and Kuznetsk basins, two various approaches have been applied: high-speed heating of the grinded raw material in a fluidized bed of catalytically active material in the air flow and thermal treatment in a fixed bed under conditions of thermal shock of anthracite that was previously subjected to chemical treatment. The highest BET specific surface (653 m²/g) and the total pore volume (0.319 cm³/g) are attained at high-speed heating of anthracite that was modified by a mixture of nitric and sulphuric acids. The sorbent yield ranges up to 84 % from the mass of initial anthracite. The produced sorbent shows predominantly microporous texture; its sorptive capacity for iodine (71 %) is at a level of commercial active coals, the obtaining of which requires a long-term energy and resource extensive stage of steam-gaseous activation.

A great amount of hemicelluloses and high density of wood of a birch hinder an application of traditional technologies to process the birch wood into cellulose. Using the catalytic acid transformations and oxidation of carbohydrates and lignin of a birch wood makes possible obtaining a series of valuable organic products. An influence of temperature, of composition of a reaction medium, of liquor ratio, of duration of processes, and of the nature of catalyst on the yield of products of acid prehydrolysis of a birch wood, of its catalytic delignification in acetic acid-hydrogen peroxide medium, and of catalytic oxidation by molecular oxygen under the alkaline conditions have been investigated. Flow diagrams for a comprehensive, environmentally sound processing of a birch wood into xylose, microcrystalline cellulose, levulic acid, vanillin, syringaldehyde, and phenolic matter that make use of the developed processes of catalytic oxidation and acid catalysis have been suggested.

The kinetics of leaching pyrrhotine solutions in sulphuric solutions containing small amount of nitrous acid was investigated. It was shown that pyrrhotine treatment under the given oxidative conditions proceeds through the stages of intensive initial and subsequent slow dissolution. The first stage is likely to correspond to the dissolution of the oxidized layer on sulphide surface and to intensive non-oxidative leaching with the formation of hydrogen sulphide. A decrease in the process rate at the second stage is due to the transition to the oxidative regime of leaching and the formation of a film of difficultly soluble compounds (oxidized iron with oxygen, elemental sulphur) on the reaction surface. The activating action of nitrous acid is likely to be exhibited at the second stage when FeSO₄ solutions are oxidized with molecular oxygen. It was shown experimentally that even small concentration of HNO₂ (0.001 M) at low temperature (293 K) causes a substantial increase in the intensity of regeneration of the active agent of chemical weathering of hypergenesis zone, namely, Fe³⁺ ions. In this connection, the system H₂O + O₂ + HNO₂ + H₂SO₄ can play a substantial part in oxidative processes in sulphide tailings. Pyrite remained almost completely non-solved in this oxidative system within the experiment duration.

The processes of fructose and saccharose conversion catalyzed by sodium hydrosulphate and sulphuric acid in biphase water-alcohol (from butanol to octanol) systems as well as in the homogeneous alcoholic media (ethanol, butanol) at 82-102^oC have been studied. It has been demonstrated by GLC-MS and ¹³C and ¹H NMR spectroscopy methods that the main products of conversion of carbohydrates are ethers and esters of 5-hydroxymethyl furfurol and levulic acid, respectively. The total yield of ethers ranges up to 80-90 mol. %. The yield of ethers drops as the concentration of carbohydrates increases. At high concentrations of substrate, the maximum selectivity of acid-catalytic conversion of fructose declines in the following succession: biphase system (water-alcohol) - homogeneous aqueous medium - homogeneous butanol solution. An increase of alcohol molecular weight causes its alkylating capacity in the studied processes to decrease. The results arrived at demonstrate that the combination of alkylation and extraction processes with the removing of the reaction products from the catalytically active aqueous phase in alcohol-water biphase systems makes it possible to increase the yield of the desired products of the process.

Investigations into oxidizing purification of subturpentine waters from sulphate cellulose production that contain hydrogen sulphide, methyl mercaptans, thiomethyl sulphides, dimethyl disulphides, turpentine, and methanol have been made. Hydrogen peroxide was chosen as an oxidizer. It has been found that hydrogen sulphide, dimethyl sulphides, dimethyl disulphides are subject to easy oxidation in the presence of H₂O₂. Methyl mercaptans and alternative organic compounds can be oxidized more effectively with the classic Fenton's reagent (H₂O₂, FeSO₄, pH 2-3) and electrochemically with the use of H₂O₂.

Bi(III) oxochloride (BiOCl) synthesized from oxohydroxobismuth (III) nitrate trihydrate and NH₄Cl, was characterized by means of X-ray diffraction analysis, chemical and thermogravimetri analyses, electron microscopy and IR spectroscopy. In the work the practical usefulness of the ultra pure bismuth (III) oxochoride synthesis from metallic bismuth was shown. This method is comprised of the following stages: metallic bismuth is oxidized by an air, forming Bi₂O₃. The latter is dissolved in nitric acid solution (1:1). Than an insoluble bismuth (III) oxohydroxonitrate trihydrate is formed and precipitate is treated with NH₄Cl and HCl solutions at (60±10) ^oC with chlorine ions:bismuth = 1:1 molar ratio. This set of procedures helps to purify the initial bismuth composition from contaminants.

The effect of minerals (montmorillonite, calcite, quartz) on the formation of group components of liquid products during pyrolysis of the kerogen of sapropel nature in benzene was investigated. It was established that the maximal amount of liquid products (with the mass concentration above 60 mass %) is formed in the presence of quartz and montmorillonite. It was established that carbonate and clayish rocks promote generation of high-molecular compounds in the pyrolyzate.

Conditions for coulometric determination of copper (II) in an extract by titration with the electrogenerated bromine have been found. 8-Mercaptoquinoline has been suggested as a complexing agent, which forms complex of composition CuR₂ with copper ions. Extraction was conducted in chloroform at ðÍ 6. The procedure is approved with synthetic mixtures and with samples of superficial waters. The lowest limit of detectable concentrations with the generating current intensity being 1^{.10-3 A and with time equal to 10 s comprises 5.10-7 M.}

Trends in the development of modern coal-chemical technologies of fuel and non-fuel consumption of coal are considered. For the Kuznetsk basin as example, some directions of deep processing of coal and waste coal materials are proposed; their practical realization is possible even at present in many coal-mining regions of Russia.