Kompleksnoe Ispolzovanie Mineralnogo Syra = Complex use of mineral resources

Morphological and Crystallographic Investigation of CVD-Grown MoS₂

2025-03-14T04:14:17+00:00

This paper presents a study of the structural characteristics of a promising MoS₂-based material obtained by chemical vapor deposition (CVD). Optimization of the synthesis process to obtain the desired structure is also presented. The optimal parameter for the synthesis of CVD MoS₂ crystals was found to be the maximum sulfurization temperature of 780 °C with an exposure time of about 15 minutes, the heating temperature of the sulfur source zone of 250 °C, the distance between the sulfur and molybdenum sources of 25 cm, and the distance between the molybdenum source and the substrate was 1.5 cm. The morphology and elemental composition of the obtained samples were studied using scanning electron microscopy (SEM) with energy dispersive X-ray spectroscopy (EDS). Using SEM, it was revealed that MoS₂ crystals are formed in a triangular shape and are evenly distributed over the surface of the substrate. The maximum sizes of crystallites reach 6 microns. EMF mapping of crystallites confirmed the homogeneous distribution of molybdenum and sulfur in the structure, revealing only minor variations in composition at the grain boundaries. The quality and quantity of the sample layer were studied using Raman spectroscopy. The results showed two characteristic peaks (vibrational modes E_2g¹ and A_1g) of nanoscale MoS₂. The peaks have a sharp shape and are located at a distance of ≈20.9 cm^-1, which may indicate the high quality of the crystal structure of the obtained crystallites. The results obtained emphasize the effectiveness of the chosen approach and the importance of the work for the development of 2D materials technologies.

Use of fly ash and ground tuff as pozzolanic additives in lightweight structural

2025-06-04T11:20:17+00:00

This paper investigates the effect of partial replacement of cement with fly ash and ground volcanic tuff on the physical and mechanical properties of concrete. The main focus is on the changes in average density and compressive strength at different contents of replacement materials (from 10% to 35%). The investigated concrete composition (27PPPF) without admixtures has an average density of 1925.5 kg/m³ and compressive strength of 40.1 MPa. The results show that when fly ash is added, the concrete strength first increases, reaching a maximum value of 41.6 MPa at 10% cement replacement and then decreases to 29.1 MPa at 35% replacement. A similar trend is observed when tuff is introduced, but the peak strength (40.7 MPa) is also reached at 10% replacement, after which the strength gradually decreases to 27.9 MPa at 35%. The average density of the specimens changes insignificantly, being in the range of 1910.4-1928.5 kg/m³, which indicates that the dense structure of the concrete is maintained. Thus, the optimum content of fly ash and tuff in the concrete composition is 10-15%, as these values provide the best mechanical characteristics. Higher dosages of substitutes result in lower strength due to thinning of cement stone and lack of binding properties. This study confirms the possibility of using fly ash and volcanic tuff as effective pozzolanic additives to improve the environmental friendliness and sustainability of concrete.

Review of Sustainable Jet Fuel Production through Pyrolysis of Waste Tires: Process, The Physicochemical Properties and Catalyst

2025-06-03T05:55:46+00:00

Solid waste, including waste tires, contributes significantly to global environmental pollution, with approximately one billion used tires generated annually. The use of waste tires as a source of sustainable aviation fuel (SAF) has the advantage of not competing with food sources, thus supporting energy needs without sacrificing food security. However, the production of jet fuel from waste tire pyrolysis oil faces major challenges to meet stringent American Society for Testing and Materials (ASTM) quality standards. This article reviews the physicochemical properties of waste tire pyrolysis oil, including viscosity, density, and sulfur content, and compares them with ASTM jet fuel specifications. A bibliometric analysis is carried out on the development of fuel research from waste tires being converted to jet fuel by collecting the number of papers and documents, the number of citations, and the countries that produce the most papers related to waste tires and their research. The development of catalysts for jet fuel production in the cracking process was also discussed in detail. The use of waste tire pyrolysis oil in jet engines was also reviewed as an initial step towards implementing sustainable fuels in the aviation sector.

Decomposition of Magnesite-Sparing Waste in Sulfuric Acid with a High Concentration: Empirical Modeling and Determination of Optimal Conditions

2025-06-04T11:28:56+00:00

This article describes the processes of decomposition of magnesite waste in sulfuric acid, which is formed during flotation enrichment of the Zinelbulak talc-magnesite deposit. As a result of the research, the influence of concentration and temperature of the reaction medium on the dissolution of magnesite in H₂SO₄ solution was investigated and melting degrees were determined. Based on the data obtained, a mathematical model of the process was formed: the melting kinetics were described by equations, and the parameters were calculated using regression analysis. The modelling results were based on the rate at which magnesite melts, mainly acid concentration, and temperature factors were studied. The value of the coefficient of determination of the constructed mathematical model justified the fact that this model was 97.2% accurate. Based on the reliability of the mathematical model, optimal conditions are determined through experimental and model analysis. The optimum conditions are a temperature of T = 81.45 °C and an acid concentration of C = 74.05%, resulting in a decomposition rate of Y_max = 93.57%. The results of this work establish a scientific foundation for treating waste products containing magnesium and producing products such as magnesium sulfate from them. Initially, the article describes the composition of raw materials and experimental methods, then the mathematical model and the results obtained are analysed, and conclusions and proposals are presented.

Calculations were performed by zeroing the first-order derivatives. As a result of the calculations, the decomposition rate is Y_max = 93.57% when the temperature is T = 81.45°С and the concentration of acidity required for the process is C=74.05%.

On the basis of the studies conducted, the model created to determine the possibility of processing magnesitic waste in sulfuric acid under optimal conditions was found and proved to be theoretically useful. This model has made it possible to use the acid decomposition process efficiently and efficiently in the studies because it operates at high precision.

Investigation of zinc leaching from clinker with pretreatment of raw materials by ultrahigh frequency radiation (microwave)

2025-03-07T13:08:14+00:00

The processing of zinc-containing man-made raw materials is an important task from the point of view of rational use of natural resources and reducing the environmental burden. In recent years, there has been a growing interest in efficient methods of processing such materials, since zinc is an important metal for industry. The leaching of zinc from raw materials with a solution of sulfuric acid is a key step in the hydrometallurgical production of zinc. Optimizing this process is crucial to increase the efficiency of its extraction, reduce costs, and minimize negative environmental impacts. We have investigated the process of leaching zinc from man-made raw materials with a solution of sulfuric acid, with pretreatment of raw materials with microwave radiation. Optimal leaching parameters have been determined. Clinker, a residual product of zinc ore calcination, was used as the starting material. The zinc content in clinker is 1.25%. It is shown that high zinc recovery is achieved after preliminary exposure to microwave radiation at a temperature of 600 °C. The effect of solvent concentration, the ratio of solid and liquid phases, and temperature on the degree of zinc extraction has been studied.

Physicochemical parameters of lithium sorption from hydromineral raw materials using synthesized inorganic sorbents

2025-03-27T05:26:23+00:00

This paper presents the results of a study on the physicochemical parameters of the lithium sorption process from hydromineral raw materials using synthesized sorbents. The physicochemical parameters of lithium sorption from brine, including the enthalpy change (ΔH, kJ/mol), entropy change (ΔS, kJ/mol·K), and Gibbs free energy (ΔG, kJ/mol), were investigated. The enthalpy value ΔH = -0.698 kJ/mol indicates that the process is exothermic, as it is accompanied by heat release. The positive value of entropy ΔS = 0.0122 kJ/(mol·K) indicates a low degree of order and increased randomness at the interface between the manganese dioxide-based sorbent and the brine during lithium absorption. The negative Gibbs free energy (ΔG) values, ranging from -4.401 to -4.769 kJ/mol at temperatures of 303–333 K, confirm that the lithium sorption process on the manganese oxide sorbent is spontaneous and can proceed without external influence. Additionally, the activation energy value Ea = -0.592 kJ/mol suggests a decrease in the sorption rate as the temperature increases. Using a modified Arrhenius-type equation, the adhesion probability S* was determined to be 0.188. This value indicates the predominance of the chemisorption mechanism in the lithium sorption process.

Study of the kinetics of sorption of praseodymium and neodymium ions using interpolymer systems based on KU-2-8 and AB-17-8 in salt forms

2025-04-22T04:36:17+00:00

This paper presents a study of the kinetics of neodymium and praseodymium ions sorption using interpolymer systems based on KU-2-8 and AB-17-8 in salt forms. Sorption of target ions was carried out in a dynamic mode (with constant stirring) in interpolymer systems in molar ratios of 4:2 and 3:3 (cation exchanger to anion exchanger). Aliquots were collected during certain time intervals, then widely known kinetic models of sorption were used to construct linear graphs. According to the obtained results, the best model for describing sorption was pseudo-first order (the highest value for the 4:2 system = 0.97885 and 0.98112; for the 3:3 system = 0.9647 and 0.98779). Such results are important for understanding the mechanisms of the sorption process and establishing the limiting factor that can slow down this process. The kinetic model of pseudo-first order may indicate the need to improve the washing out of counterions from the polyelectrolyte matrix for their high ionization and accessibility of functional groups for metal ions. This assumption can be used in the future to optimize industrial schemes of ion-exchange sorption of REE.