Title: Synthesis and characterization of polypropylene glycol-graft-styrene
Abstract: Grafting polymerization based on polypropylene glycol (PPG) and styrene (St) was synthesized with different composition of styrene using the free radical technique in the presence of potassium persulphate as an initiator. The grafted copolymers (PPG-g-St) used different styrene composition (65/15, 65/25, 65/35), respectively. The grafted copolymers were investigated through FTIR (Fourier-transform spectroscopy), Differential scanning calorimeter and thermogravimetric analyzer. FTIR showed new peaks at 1450 cm-1 and 1135 cm-1 due to the grafting process of St on PPG. Thermal stability of grafted copolymer increases by increasing the ratio of styrene, while Tg decreases by increasing the ratio of styrene.
Keywords: Grafting, polymerization, styrene, copolymer, radical.
Title: Adsorption methods for the extraction and seperation of rare earth elements. Review
Abstract: Rare earth elements play an important role in the production, energy, and high technology. Due to the rapid development of industry, the demand for rare earth metals is rising every day. Therefore, it is necessary to improve the extraction of rare earth metals from various sources to meet the demand for these elements. Currently, pyro- and hydrometallurgical technologies are used to extract rare earth metals from an ore and other secondary sources (industrial wastewater, acid drainage mines, etc.). Hydrometallurgical technologies include precipitation, extraction, adsorption, and ion exchange methods. Adsorption is one of the most effective methods for the extraction and separation of rare earth elements. Adsorption methods are highly selectivity to metal ions and have low emissions. However, not all adsorbents are effective in producing the same metal ions. This study provides an overview of the different adsorbents that can be used to extract rare earth elements from aquatic systems. Hydrogels and molecular polymers have been found to be cost-effective methods for high-grade rare earth metals. Further research is needed to ensure the performance of these systems.
Keywords: rare earth elements, adsorption, adsorbent, hydrogel, molecular polymers.
Title: Thermodynamic modeling of the synthesis of the main minerals of cement clinker from technogenic raw materials
Abstract: In this article, thermodynamic studies of modeling the formation of the main minerals of cement clinker as a function of the Gibbs energy (ΔG) on temperature were investigated. The temperature range of the studies was 873-1873 K. In the course of modeling studies, the reactions of formation of cement clinker minerals (C2S - belite, C3S - alite, C3A – three calcium aluminates, C4AF – four calcium aluminium ferrite) from standard raw materials and non – standard-technogenic raw materials containing non-ferrous metals were calculated. Equations describing the dependence of the Gibbs energy on temperature with approximation coefficients (R2) equal to 0.99 are found. According to the results of the conducted studies, the beginning (Tb) temperatures of the course of the compared clinker formation reactions were determined, which were 1008 K for the standard reaction, and 1023 K for the non-standard reaction. It was found that the reactions begin to occur in the temperature intervals for the standard (1008 K – 1873 K), for the non - standard (1023 K - 1873 K). At the same time, the values at the initial stage of the course of the standard reaction have a more negative value of the Gibbs energy than the non-standard reaction. With a further increase in temperature, it becomes evident that the Gibbs energy of the non-standard reaction of mineral formation in the temperature range 1173-1873K becomes more negative in comparison with the values of the standard reaction and exceeds its values from 9 to 19.01%.
Keywords: Technogenic raw materials, processing waste, thermodynamics, Gibbs energy, cement clinker minerals, non-ferrous metals.
Title: Metallurgical processing of converter slag
Abstract: Converter slurries at modern metallurgical plants represent a significant part of metal-containing industrial waste with a high concentration of iron. Currently, there is a problem of their utilization and use as raw materials for metallurgy. The purpose of this work is to study the processes of briquetting and recovery of briquetted products, based on a mixture of converter slurries of gas purification and converter slags. When performing experimental studies on the preparation of sludge briquettes from a mixture of converter sludge of gas purification and converter slag, their metallization and reduction melting in laboratory conditions, the optimal composition of the components of the mixture of converter slag and gas purification sludge was determined by the percentage of iron, which is appropriate for use as a raw material for steel smelting. Experimental studies on the preparation of sludge-coal mixtures from dispersed metal-containing and carbon-containing industrial waste with stoichiometric coal consumption for the recovery of extracted metals have proved the possibility of obtaining sludge-coal briquettes, which are further subjected to metallization and reduction melting. Sequential processing of dispersed production waste, namely drying, metallization and reduction melting, allowed us to obtain at the final stage a metal sample that corresponds to high-quality steel in its composition. Based on the analysis of the results of experimental studies, the technology of reducing melting of metal-containing waste has been developed. As a result of the implementation of the technology, high-quality steels and alloys can be obtained without carburizing the metal, bypassing the production stages of cast iron and high-carbon alloys. The content of harmful impurities of sulfur and phosphorus meets the technical requirements of high-quality steel. The proposed technology for processing slag and sludge from oxygen-converter production will reduce the volume of accumulated production waste.
Keywords: converter slag, converter sludge, coal sludge, briquette, recovery, smelting.
Title: Ferroalloy production from ferrosilicon manganese dusts
Abstract: The article presents the results of studies on the influence of time, the amount of steel shavings and coke on the electric melting of ferrosilicon manganese dusts to obtain a ferroalloy. The research was carried out by the method of rotational planning of the second order (Box-Hunter plans) and by electric smelting of dust in laboratory ore-thermal arc furnace. Dust from the production of ferromanganese by LLP Taraz Metallurgical Plant, coke and steel shavings were used during the research. It was determined that to achieve αSi≥70%the process must be carried out in the presence of 25% coke and 8.1-9% steel shavings from the mass of dust for 55.8-60 minutes, to achieve αMn in an alloy of 80-85% the process must be carried out in the presence of 25% coke, 5.7-9.0% steel shavings for 41.2-54.4 minutes. When melting the charge containing 75.2% of dust, 18.8% of coke, 6% of steel shavings, within 60 minutes the weight of the ferroalloy was 258 g (38.8% of the weight of the charge or 51.6% of the weight of dust). The degree of extraction of manganese into the alloy was 82.3%, silicon - 66.1%. The resulting ferroalloy belongs to ferrosilicon manganese of the FeMnSi12 grade.
Keywords: dust, ferrosilicon manganese, steel shavings, coke, electric smelting.
Title: Dissolution of iron in sodium chloride solution during alternating current polarization
Abstract: Iron compounds are widely used in many industries and engineering, and even in medicine. The existing methods of obtaining iron compounds are multi-stage and complex. The purpose of this work is to obtain iron (II) hydroxide and oxide from metal waste under alternating current action using one and two half-cycles. For the first time, the electrochemical behavior of iron electrode was studied by electrolysis method during alternating current polarization of industrial frequency in sodium chloride solutions. The iron polarization was carried out in pair with titanium, while the current density on the iron electrode varied in the range of 200-1200 A/m2, and on the titanium is in the range of 20-100 kA/m2. It is established that in the anode half-cycle of alternating current, iron is oxidized to form divalent ions. At this moment, the titanium electrode is in the cathode half-cycle, hydrogen is released on it, hydroxyl ions are formed in the cathode space. In the solution, ions interact with iron (II) ions to produce iron hydroxide. At temperatures above 600C, iron (II) hydroxide is dehydrated with the production of iron (II) oxide. The electrolysis was carried out in two electrolyzers connected to each other in parallel with the immersion of pair of “titanium-iron” electrodes into each electrolyzer. The iron dissolution occurs simultaneously in two half-cycles of alternating current and this approach is proposed for the first time. The process productivity increases by more than 1.5 times.
Keywords: iron, titanium, electrode, alternating current, two half-cycles, hydroxide, iron oxide.
Title: Investigation of the properties of composite materials based on epoxy resins with microsilica additives
Abstract: The outcomes of studying epoxy-based composite materials supplemented with microsilica are provided in the article. Microsilica was used as a filler. The samples were produced on the epoxy ED-20 basis supplemented with 2, 5 and 10 mas. % of microsilica. The structure and size of finely dispersed filler particles were defined. The obtained composites were tested for resistance to the effect of variable temperatures, corrosive, and abrasion. The study outcomes proved that samples supplemented with 2% of microsilica are more resistant to acid and alkali as well as to petrol than those ones supplemented with 25% of microsilica. Besides the amount of the filler from 2 to 10% doesn’t sufficiently affect the resistance to variable temperatures. When microsilica is added to epoxy resin, it causes scuff resistance increase. The conducted testing proved that the developed composite materials are resistant to the effect of variable temperatures, corrosive, and abrasion. This enables to use these materials as coatings and anti-corrosion protection during machine maintenance.
Keywords: epoxy resin, microsilica, filled composite material, chemical resistance, composite material, corrosive, abrasion, coating.
Title: Study on the behavior of zinc and associated metal-impurities in the process of chlorinating roasting of dross
Abstract: In this work the issue of processing of dross with preliminary separation of the metal part from the oxide one is reviewed. Based on a comparative analysis of the results of known works it is shown that this approach can be quite effective if a technology is developed for the separate processing of the oxide part to obtain a commercial product. The authors of this work proposed carrying out chlorinating roasting under oxidizing conditions with various chlorine-containing reagents as one of the effective ways of processing the oxide part of the dross. Based on the thermodynamic analysis of the reactions of interaction between the components of the oxide part of the dross and calcium and ammonium chlorides, the principal possibility of obtaining pure zinc oxide, suitable for use as mineral additives in animal feed has been shown. As a result of thermodynamic calculations of the reactions of interaction of impurity metals with calcium chloride and ammonium chloride, the values of Gibbs free energy and reaction rate constants were determined in the temperature range 973 and 1373 K. It has been established that under the conditions of roasting the oxide part of the dross with both calcium chloride and ammonium chloride, a high degree of sublimation of impurity metals from the dross in the form of their chlorides into dust is achieved. It has been shown that roasting the oxide part of the dross using ammonium chloride is more efficient than with calcium chloride.
Keywords: Dross, metallic zinc, zinc oxide, roasting, thermodynamics, impurity metals, Gibbs free energy, calcium chloride, ammonium chloride.
Title: Modeling of heat transfer in a fuel pellet based on uranium dioxide and ceramics (beryllium oxide)
Abstract: The results of heat transfer mathematical model calculations in the “UO2-BeO” pellet are presented. The fuel pellet consists of uranium dioxide (UO2) and beryllium oxide (BeO) ceramics. Modeling of heat transfer was carried out by a system of generalized heat conduction equations with variable thermophysical properties. The calculated data of the temperature field in the fuel pellet were obtained using the COMSOL Multiphysics software code. The results of temperature calculations were compared with the data of other authors. The agreement of the calculated data shows the mathematical model and the COMSOL Multiphysics code algorithms correctness. Various arrangements of beryllium oxide ceramics BeO in a fuel pellet are considered. The arrangement of the BeO ceramics in the centre of the fuel pellet showed a noticeable decrease in temperature in the energy release zone. Calculations have shown that the composite fuel “UO2-BeO” is the most effective for regulating the thermal regime of fuel elements.
Keywords: heat transfer modeling, fuel pellet, uranium dioxide, beryllium oxide ceramics.
Title: Mathematical model of coal self-heating in a stack
Abstract: The article presents a mathematical model of coal self-heating in the stack in which the heat exchange and gas exchange processes are described by a system of two non-linear differential equations of the second order with respect to the temperature t of coal self-heating and the volume fraction C of oxygen in the voids of the stack with boundary and initial conditions. The differential equations took into account that self-heating of coal in the stack and appearance of spontaneous combustion are observed in a relatively small layer adjacent to the surface of its contact with the air and called the zone of oxygen influence. In the mathematical model, the influence on the process of coal self-heating of parameter F- specific heat release power was taken into account, which in addition characterises the stability of coal during storage. When compiling the differential equations, such physical parameters as thermal conductivity, diffusion coefficient, specific heat capacity of coal in the stack, bulk density, thermal effect of oxidation, stack voidness, temperature coefficient of exponential growth of heat release power were also used. For numerical implementation of the mathematical model, dimensionless variables and criteria were introduced, which allowed us to apply the net method. Analysis of the obtained results allowed to get: change in the stack temperature profiles with time; change in the stack oxygen concentration profiles with time; influence on the stack temperature profile of the specific heat release power; influence on the stack temperature profile of the parameter characterizing exponential growth of heat release intensity with temperature increase. It has been determined that the dynamics of coal self-heating in the stack is mostly influenced by the Lykov criterion, proportional to the diffusion coefficient, and the Nusselt criterion related to the effective thermal conductivity and to the effective thermal diffusivity of coal. The obtained results suggest that self-heating in the stack is due on the one hand to intensive penetration of air oxygen and on the other hand to a weakened heat transfer. Self-heating and the transition of self-heating into ignition are associated with the occurrence of turbulent diffusion in the stack, arising from increased thermal blowing, whose impact can be enhanced by directing it perpendicular to the surface of the stack.
Keywords: self-ignition, stack, self-heating in the stack, heat and gas exchange processes, coal self-heating.
Title: Recovery of niobium from wastes generated in titanium production by cation exchange sorbents
Abstract: This article presents the technology of niobium recovery by processing of chloride residues generated during the chlorination of titanium slags. For waste processing, a two-stage leaching technology is proposed. Water is used at the first stage of leaching and hydrochloric acid 4.0 M is used at the second stage. For the purpose of sorption of niobium from the solution composition obtained during leaching, cation-exchange sorbents Purolite-C104 and KU-2-8 H were used. By the usage of Purolite-C104 ion exchange resin the sorption efficiency of niobium from a solution with a concentration of 2 g/l was about 71.0 % (0.071 g/g) in 3.5 hours, while for KU-2-8 H ion exchange resin, sorption efficiency was about 89.0 % (0.089 g/g).
Keywords: chloride wastes, leaching, niobium sorption, cation exchange sorbents.