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Optimization of the flow part of the microfluidic channel

https://doi.org/10.58224/2619-0575-2024-7-2-4-12
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 4-12 p.
Abstract
In this paper, the features of microfluidic channel optimization are considered. The microfluidic channel is a key component of the microreactor, its shape and features of the hydrodynamic regime directly affect the successful course of chemical reactions carried out in it. The microfluidic industry regulates processes occurring in small volumes of liquids – on the order of a nano liter or less. It is applicable to various fields such as microelectronics, pharmaceuticals, specialty chemicals, etc. The Comsol Multiphysics computational modeling program was used as an optimization tool. It is based on the finite element method, which allows you to accurately model the problems of the hydrodynamic profile. In this article, the simplest form of a microchannel is considered – a 0.75 mm circular channel with a mixing cell. The mathematical modeling of the process is given, the optimality criterion adequate for the task is determined. As one of the components of this criterion, diodicity was used – a criterion that determines the ability to pass a stream in the forward direction, provided there is a reverse flow. As a result of this work, the most optimal shape of the microreactor channel satisfying the required process conditions was identified, the main hydrodynamic parameters were obtained and the dependence of the diode on the criterion used was determined.
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The influence of hydrogen injection together with methane on changes in the physicochemical properties of sandstone

https://doi.org/10.58224/2619-0575-2024-7-3-137-145
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 137-145 p.
Abstract
The scientific basis of hydrogen storage in the environment, the causes and mechanisms of its interaction with other natural gases and fluid-containing media are poorly developed. Therefore, it is important to conduct a set of studies aimed at clarifying the main factors of its storage in UGS facilities together with methane. Changes in the physico-chemical properties of a sandstone sample after prolonged exposure to a hydrogen-methane mixture have been studied using infrared spectroscopy (IR), nuclear magnetic resonance (NMR), X-ray fluorescence analysis, and velocity measurement of longitudinal and transverse sound waves. Changes in the composition of the rock are confirmed by differences in the IR, NMR, and transformation spectra of the mineral component of sandstone, which is largely due to the crystallization processes of substances dissolved in adsorbed water. The results of these studies can be used in the planning and operation of underground gas storage facilities in regions where large-scale hydrogen production and storage will be organized.
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Electrophilic-nucleophilic and hydrophobic properties of surface-modified metals

https://doi.org/10.58224/2619-0575-2024-7-2-13-25
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 13-25 p.
Abstract
The method of layering different-sized molecules of ammonium and organosilicon compounds on metals, developed at the St. Petersburg Mining University, is a promising method for hydrophobization and stabilization of the surface properties of dispersed metal materials. A comparison was made of the hydrophobicity of samples based on PMS-1 copper powder processed in pairs of modifiers in mixed or sequential modes. To provide a physicochemical substantiation of the mechanism of surface hydrophobization, quantum chemical modeling and assessment of the electrophilic-nucleophilic properties of isolated modifier molecules in the HyperChem software package, as well as their adsorption interaction with a cluster model surface in the Gaussian 09 software package, were carried out. It was established that the adsorption energy values lie in range 64–127 kJ/mol, which corresponds to the chemical interaction of ethylhydride siloxane molecules and quaternary ammonium compounds (QAC) with the metal. It has been established that samples containing modifiers with different electrophilic-nucleophilic properties in the surface layer of the metal are characterized by better hydrophobicity. Also, the key role of QAC in the hydrophobization of the surface has been established by providing a stronger heteroatomic interaction with the metal surface and the formation of a preparatory QAC sublayer for structurally similar functional groups.
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Study of sorption properties of silicon dioxide based on overburden rocks for the extraction of dyes from wastewaters

https://doi.org/10.58224/2619-0575-2024-7-2-26-42
 26-42 p.
Abstract
The article presents the results of a study of the sorption properties of silicon dioxide obtained from overburden rocks for use in the removal of methylene blue, an organic cationic thizian dye, from aqueous solutions. The aim of the study was to evaluate the sorption properties of silica and its efficiency in the removal of methylene blue from aqueous solutions. Experimental data showed that the sorption efficiency depends on temperature, pH and stirring speed. It was found that increasing pH and stirring speed promotes sorption enhancement, while increasing temperature decreases sorption efficiency. In addition, the possibility of regeneration of silica after sorption was investigated and it was shown that its sorption properties are practically unchanged after several cycles of use. The maximum sorption capacity was 515.9 μmol/g. In a previously published paper, under standard conditions, the maximum sorption capacity was 438.22 μmol/g. The results emphasize the potential of silica as an effective and sustainable sorbent for the removal of organic dyes from wastewater. Thus, silica can be recommended for multiple use in wastewater treatment processes due to its high thermal stability and durability.
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Optimization of a typical condensation process using the example of isophorone synthesis in a microchannel

https://doi.org/10.58224/2619-0575-2024-7-2-43-52
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 43-52 p.
Abstract
The work is devoted to the method of obtaining isophorone in a microchannel. Numerical and experimental optimization of the process of obtaining isophorone in a microchannel has been carried out. Isophorone is an unsaturated cyclic ketone, widely used in industry as a solvent for nitrocellulose paints, as well as as an inter-mediate for the synthesis of other compounds. The synthesis was carried out in microchannels. Microchannels are channels with a diameter of less than 1 mm. Their main feature is the possibility of carrying out various types of reactions requiring high pressures and temperatures. Due to the small internal volume, all processes occurring in them are easily intensified, high accuracy and efficiency of the experiment can be achieved. Parameters such as reaction temperature and reagent consumption varied. A new approach to conducting the experiment was used, based on minimizing the control parameters used and combining them correctly. This approach requires high ac-curacy and reproducibility of the results, so the microchannels used in this work are the best choice for such tasks. A mathematical model of the reaction based on systems of equations of varying complexity has been developed. Three-dimensional and two-dimensional contour diagrams are constructed to visualize the mathematical model of the process. The best technological parameters of the process have been established.
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Composites materials based on natural chrysotile fibers

https://doi.org/10.58224/2619-0575-2024-7-1-4-21
 4-21 p.
Abstract
The article discusses the technology of production, the problems of the development of chrysotile and chrysotile cement industries in the CIS countries. The article provides information on the composition and properties of natural chrysotile fibers, data on the quality of raw materials of cement and chrysotile fibers supplied to chrysotile cement enterprises, characteristics of suspension with them, semi-finished product and properties of solidified chrysotile cement products.
The purpose of the research is to study the influence of external and internal factors, risks on the development of the chrysotile-asbestos industry, on the sales market. Identification of the dependence of the influence of the pa-rameters of chrysotile fiber and cement on the quality of finished chrysotile cement products.
Analysis of scientific literature, analysis of current production, identification and monitoring of the quality of raw materials and finished products, comparative analysis of production and consumption markets.
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Quantum model of anharmonic vibrations of a diatomic molecule with a variable force constant and a small value of the anharmonicity coefficient

https://doi.org/10.58224/2619-0575-2024-7-1-22-31
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 22-31 p.
Abstract
In this work, vibrations of a diatomic molecule are considered within the framework of quantum mechanics as an anharmonic oscillator with small values of the anharmonicity coefficient. Based on well-known models of quantum harmonic and anharmonic oscillators, a new model with a variable value of the molecule force constant was created here. The force constant depends on the vibrational quantum number n and the anharmonicity coefficient . Mathematical analysis of this model confirmed its physical validity. As an example, the vibrational energy of an oxygen molecule was calculated within the framework of the model presented in the work.
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Application of thermal methods for the analysis of organic matter content in urbanozems

https://doi.org/10.58224/2619-0575-2024-7-1-32-40
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 32-40 p.
Abstract
Objectives: the purpose of the study is to determine the content of organic matter in anthropogenic soils using thermal analysis methods.
Methods. Physico-chemical methods of soil sample analysis were used, the actual acidity, ash content and or-ganic matter were determined according to GOST 26213-2021 and by thermogravimetric analysis.
Results. It is shown that the content of organic substances in soils by thermogravimetry and according to GOST 26213-2021 differ by no more than 15.4%, which, in particular, may be due to the decomposition of inorganic sub-stances during prolonged exposure at a temperature of 525 ° C according to the GOST method. Nevertheless, the thermogravimetry method provides information about the temperatures at which the maximum decomposition rate is observed.
Conclusions. It has been established that the methods of thermogravimetry and according to GOST 26213-2021 give different results of the content of organic carbon in the soil due to different temperatures of maximum decom-position of humic acids. The higher the maximum decomposition temperature, the less organic substances decom-pose when studying soils by thermogravimetry.
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Structural parameters of YBa2Cu3-xO6+y

https://doi.org/10.58224/2619-0575-2024-7-1-41-48
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 41-48 p.
Abstract
the aim of the work is to study the structural parameters of phase 1-2-3 by precision X-ray diffraction method. The refinement of composition and structural parameters to the divergence factor R = 0.008 was carried out. The composition of the substance can be expressed by the formula . Higher values of the mean-square amplitudes of atoms vibrations and vibration anisotropy were obtained for Си1 and О1 located in the basis plane z = 0. Comparison with data obtained at low temperatures suggests that the high mobility of Си1 and O1 is related to static displacements of atoms from their crystallographic positions. There is a correlation between the deviation from the oxygen stehiometry, the lattice period c and the value of the superconducting transition temperature Tc. An increase in the oxygen content is accompanied by an increase in Tc. Dependences of isotropic mean-square amplitudes of atoms-components vibrations of compounds on the oxygen content are plotted. For the O1 atom in the tetragonal phase, a marked growth of mean-square amplitudes of vibrations with increasing oxygen index is observed, which may be associated with an increase in the instability of the structure. It can be concluded that the analysis of precision diffraction studies for yttrium-barium-copper oxides allows us to identify the structural features responsible for the instability of this class of materials.
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Analysis of the effect of technological parameters on desulfurization of agglomeration charges

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 5-17 p.
Abstract
This paper presents an analysis of the influence of technological parameters such as temperature, basicity and carbon content on the degree of desulfuration (removal of sulfur) during agglomeration of iron ore raw materials, which in the future will help to detect and calculate the most effective mode of operation of firing conveyor and sintering machines during heat treatment and processing of mineral iron ore raw materials. It was found that the most significant effect on the desulfurization of fluxed sulfate-containing charges is to reduce the size of the ore and the introduction of fusible additives that reduce the viscosity of the slag. It was revealed that the effect of the first factor is limited by the capabilities of crushing departments of mining and processing plants and the difficulties of sintering fine-grained charges, and a decrease in the fusibility of the sintering charge can lead to a deterioration of combustion processes and a drop in the technical and economic indicators of the sintering process. Gorenje It was found that the implementation of additional measures to obtain low-sulfur agglomerate from sulfate-containing ores is hampered by the lack of research on the kinetics of the main reactions that determine the final sulfur content in the agglomerate. It has been shown that dissociation of calcium and barium sulfates in contact with silicon, iron and aluminum oxides is possible at temperatures of 1000-1100°C. It was found that the dissociation of sulfates proceeds at a rate that ensures an increase in the degree of desulfuration. A decrease in the degree of desulfurization is observed in the temperature range of1200-1300°C, due to liquid-phase contact with silicon, iron and aluminum oxides. It was found that further studies of the kinetics of thermally activated reactions of high-temperature dissociation of barite and calcium sulfate under conditions close to agglomeration processes in operating heat treatment units of iron ore raw materials are necessary to increase the degree of desulfuration of sulfate-containing fluxed agglomeration charges.
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