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Specific features of the pyridine structure make it a convenient model system to describe coal combustion; however, the main attention of researchers has been paid to the formation of the ortho-pyridyl, whereas the formation of meta- and para-pyridyls has been yet poorly studied. The rate constants of the formation of three pyridine radicals by hydrogen atom abstraction by another hydrogen atom are compared. The geometry of the reactants is optimized within the framework of the density functional theory with subsequent refinement of single-point energies by the ab initio G3(MP2,CC) hybrid method. The calculations show that the formation of ortho-pyridyl is preferable, though the formation and further transformations of all three radicals should be taken into account for a detailed description of the coal combustion process.

The article describes the tests of thermal treatment effects on magnetic properties of bauxites and the results of their dry magnetic separation. Under increasing temperature in a muffle furnace to 600 °С, the magnetic susceptibility of treated bauxites decreases. The thermal radiation modification of bauxite by accelerated electrons under the same temperature improves the magnetic properties of the mineral. Magnetic separation efficiency is governed by the thermal treatment conditions. The process parameters to ensure extraction of rare and rare earth elements to the magnetic fraction are found.

In this study, modeling and optimization tests were conducted on enrichment of chromite ore by Knelson concentrator. For this purpose, the three-level Box-Behnken experimental design method was applied. The analysis of variance (ANOVA) was used at 95% confidence interval to test the significance of independent variables and their interactions. In order to estimate the chromite concentrate grade and chromite concentrate recovery with independent variables, quadratic polynomial regression equations were derived. Maximum concentrate grade of 54.77% and concentrated recovery values of 77.1% were reached in 12 l/min fluidization water flow rate, 1124.57 rpm bowl speed, and 21.05% solids ratio. The coefficient of multiple determination (R²) was calculated as 0.996 for concentrate grade and 0.991 for concentrate recovery. This indicates that the proposed model is a usable and effective model.

The monomineral extraction of molybdenite and stibnite is tested and analyzed using non-frothing flotation, adsorption, IR spectroscopy, multiple frustrated total internal reflection and potentiometric measurements. The ionized sulfhydryl collectors tested at concentrations of 10^-4 mole/l in a pH range of 2-12 include butyl xanthate, diisobutyl dithiophosphate, diisobutyl dithiophosphinate and sodium diethyldithiocarbamate. The test nonionized collectors are diesel fuel and O-isopropyl-N-ethyl thionocarbamate. Molybdenite shows higher floatability than stibnite in application of individual collectors in a pH range of 4.5-8.0. Stibnite is better floatable with diisobutyl dithiophosphate, while molybdenite flotation is more active with diesel fuel. The general critical concentration found for the modifiers H₂O₂ and Na₂S₂O₃ is 4.4·10^-3 mole/l-the flotation activity of molybdenite and stibnite is minimal at this concentration of the agents. Different sorption forms of the ionized sulfhydryl collectors are proved by the multiple frustrated total internal reflection infrared spectroscopy. Anisotropism of mineral electrodes Sb₂S₃ and MoS₂ made along and across the crystal lattice cleavage is experimentally confirmed. The ratio rating of grains of low-oxidizable sulfides, broken along the cleavage or in other direction relative to the cleavage, can modify the process properties of molybdenite and stibnite.

The influence of coarseness of magnetite is examined in iron concentrates after wet sieving analysis. The test concentrates are the products of Olkon, Karelskiy Okatysh and Stoilensky GOKs. It is shown that magnetic susceptibility of the concentrates gradually reduces with the decreasing size of magnetite particles in the material < 50 µm and assumes the minimal values in the sieve residue < 8 µm.

The article describes the studies into the mineralogy and process properties of ROM gold-copper-porphyry ore from the Svoboda site of the Malmyzh deposit in the Khabarovsk Krai. The tests and analysis reveal the structure and texture, and mineral composition of the ore, as well as the occurrence forms of gold and silver. The ore characteristics which govern the difficulty of the selective flotation are determined. Efficiency of Cu, Au and Ag extraction in the bulk and copper flotation cycles is described, and the causes of loss of the minerals are discussed. The resultant copper concentrate contains gold and silver, while the presence of Bi, Te, Se and admixture of In, Cd in chalcopyrite add to the value of the concentrate. Magnetite extracted from the bulk flotation tailings contain some platinum (0.5-2.0 µm) and admixtures of Ti, V, Mn, Cr and Cu.

The authors appraise application of milky quartz from the Larino lode deposit in production of high-purity quartz concentrate with the total content of impurities less than 50 ppm. The structure and texture of milk quartz are analyzed using the optical microscopy and ICP-OES spectrometry methods. The elemental analysis data of the preconcentration and deep concentration products are compared. The low contents of the impurity elements in the deep concentration products of quartz from most lodes of the Larino deposit prove the applicability of this quartz material as a feedstock for the production of high-purity quartz concentrates.

The authors discuss feasibility of high-tonnage direct inclusion of overburden in composites for the construction of road layers at mines. It is found that overburden has a strength as per State Standard GOST 23558-94 and the prolonged dedusting effect. The optimal contents of the binder and fly ash are 8 and 10% by mass, respectively. Mechanical activation of fly ash for 1 min enlarges its specific surface by 2 times. The frost-resistant composites modified with mechanically activated fly ash and stabilizer (1% by mass) have the strength grades M20-M40.

The scope of overburden investigation embraces overburden volume, physical state, mineralogy and chemistry, content of toxic elements, hydraulic/thermal/physical/mechanical properties, compositional analysis and potential process flows with a view to manufacturing materials of construction. It is found that the mineral and chemical compositions of overburden in coal mining are the same as the mineral raw material has, and the content of toxic elements is within the allowable concentrations. These rocks are classified as modulus-active and highly active, and are thermally inert. The integrated processing of overburden in coal mining enables using these rocks as a feedstock for the production of heat-insulating, ceramic, binding and road construction materials.

Tripolium genus is represented by the only species Tripolium pannonicum (Jacq.) Dobrocz. The individuals of this species feature variable morphological characters due to wide distribution area of the species covering vast territory from the Atlantic coast of Europe through the Pacific Ocean. As a typical halophyte, it grows in azonal communities of several latitude zones. The study was based on the analysis of morphological characters which used to be diagnostic in distinguishing between the closely related taxa: T. pannonicum (Jacq.) Dobrocz. subsp. tripolium (L.) Greuter. (T. vulgare s. str.) and T. pannonicum (Jacq.) Dobrocz. subsp. pannonicum. The significance of morphological diagnostic characters in protologs and subsequent botanical literature is discussed. Such morphological characters as presence/absence of heterocarpy and stem branching pattern are stated to be independent of geographical distribution of populations. They rather represent an adaptive character of propagation in annual plants of Tripolium pannonicum (Jacq.) Dobrocz. under variable environmental conditions of under flooding zone.