Iron And Steel Research Articles

The Application of Lignocellulosic Biomass Waste in the Iron and Steel Industry in the Context of Challenges Related to the Energy Crisis

The Application of Lignocellulosic Biomass Waste in the Iron and Steel Industry in the Context of Challenges Related to the Energy Crisis

The nature of some Late Bronze Age iron-bearing artefacts of the Ural-Kazakhstan region

The problem of the beginning of iron production in the Late Bronze Age of the Ural-Kazakhstan region is dis-cussed. For this, 13 iron-bearing artefacts from nine settlements that functioned in the 2nd mil. BC were studied using the SEM-EDS and LA-ICP-MS methods: metal objects, metallurgical slags, and a bimetallic droplet. Most of the studied artefacts are not related to the iron metallurgy. High ferric impurities in copper metal products of the Late Bronze Age on the territory of the Southern Trans-Urals are caused by the use of iron-rich ore concentrates. The raw materials for these products were represented by mixed oxidized-sulphide ores from the cementation subzone of the volcanogenic massive sulphide and skarn copper deposits. Iron droplets, frequently found in the Late Bronze Age copper slag in the Ural-Kazakhstan region, are not directly related to iron metallurgy. They are by-products of the copper metallurgy formed in the process of copper extraction from the iron-rich components of the furnace charge or fluxes (brown iron ore, iron sulphides). The only artefacts that indicate direct smelting of metal from iron ore are the slag fragments from the Kent settlement. Presumably, oxidized martitized ore of the Kentobe skarn deposit or its nearby analogues was used to extract iron at the Kent settlement. Rare finds of iron slags from the Late Bronze Age, known only in the territory of Central Kazakhstan, confirm an extremely small scale of iron production. Iron ore had been already deliberately used for these experiments. However, iron metal-lurgy in the Ural-Kazakhstan region developed into a mature industry much later. The discovery of iron metallurgy based on the smelting of copper-sulphide ores in the Ural-Kazakhstan steppes is doubtful. The use of sulphide ores here is known from the 20th c. BC, and it was widespread. In the meantime, the first iron slags and products appear much later, and their finds are sporadic. The development of iron metallurgy on the basis of experiments with iron ores seems more likely.

Application of ultrasound-assisted technique for production of mesoporous magnesium oxide from solid waste of ductile iron: An alternative method for elimination of surfactants from precipitation process

In the present work, the mesoporous magnesium oxide nanoparticles were produced from the solid waste of ductile iron casting industry. Mg2+ ions were extracted from the waste through the acid leaching, and MgO nanoparticles were obtained by the conventional, and ultrasound-assisted methods. Mg(OH)2 nanoparticles was precipitated in the presence of sodium dodecyl sulfate/Triton, 1:1, and under ultrasound irradiation in the absence of mentioned surfactant. The precipitates were then converted to mesoporous MgO via the calcination at 500 °C. The structure of products was evaluated by X-ray diffractometry (XRD), field emission electron microscopy (FESEM), and N2 adsorption-desorption isotherms. Although MgO nanoparticles with the specific surface area of 118 m2 g−1 could be fabricated by the conventional precipitation, the surfactant concentration should be fixed at the level of 1.5 g L−1. The precipitation under ultrasound irradiation is suggested for the clean fabrication of highly porous powder, 0.7586 cm3 g−1, in which the pore diameter is distributed in the range of 2–12 nm. In consequence, the solid waste of ductile iron industry is a potential material for the fabrication of mesoporous MgO by ultrasound- assisted technique in the absence of surfactant.

Recent advances in sulfidized nanoscale zero-valent iron materials for environmental remediation and challenges.

Over the past decade, sulfidized nanoscale zero-valent iron (S-nZVI) has been developed as a promising tool for the remediation of contaminated soil, sediment, and water. Although most studies have focused on applying S-nZVI for clean-up purposes, there is still a lack of systematic summary and discussion from its synthesis, application, to toxicity assessment. This review firstly summarized and compared the properties of S-nZVI synthesized from one-step and two-step synthesis methods, and the modification protocols for obtaining better stability and reactivity. In the context of environmental remediation, this review outlined an update on the latest development of S-nZVI for removal of heavy metals, organic pollutants, antibiotic resistance genes (ARGs), and antibiotic resistant bacteria (ARB) and also discussed the underlying removal mechanisms. Environmental factors affecting the remediation performance of S-nZVI (e.g., humic acid, coexisting ions, S/Fe molar ratio, pH, and oxygen condition) were highlighted. Besides, the application potential of S-nZVI in advanced oxidation processes (AOP), especially in activating persulfate, was also evaluated. The toxicity impacts of S-nZVI on the environmental microorganism were described. Finally, the future challenges and remaining restrains to be resolved for better applicability of S-nZVI are also proposed. This review could provide guidance for the environmental remediation with S-nZVI-based technology from theoretical basis and practical perspectives.

Iron-material-facilitated methane production from anaerobic wastewater treatment

Various iron materials have been used to improve the methane production rate in anaerobic sludge. The effects of iron materials, including zerovalent iron (ZVI), magnetite (iron (II,III) oxide (Fe3O4)) and iron (III) oxide (Fe2O3), on the methane production rate were compared. It was found that all the iron materials could improve the methane production rate, and ZVI, iron (II,III) oxide and iron (III) oxide increased the methane production rate by 19.8, 13.7 and 17.9%, respectively, in which ZVI performed best in improving methane production. Then, the long-term effects of ZVI on the methane production rate of anaerobic organisms were further studied. ZVI increased the methane production rate by 7.2%. The improvement was unstable and decreased due to corrosion and loss of ZVI in the anaerobic wastewater-treatment system. The improved performance was recovered after ZVI was re-added into the anaerobic sludge; the methane production rate increased by 6.1%. The added ZVI obviously enriched the exoelectrogenic archaea Methanobacterium due to its ability of direct interspecific electron transfer, and the relative abundance of Methanobacterium was up to 61.99%. Enhanced direct interspecific electron transfer was revealed as the main mechanism involved in enhanced methanogenesis in anaerobic sludge.

Хімічні канцерогени у навколишньому середовищі України: ризик для населення, шляхи попередження, удосконалення гігієнічного регламентування

The purpose of this work was to determine the carcinogen-hazardous factors in the environment and the criteria for assessing their danger to the population in modern conditions (pre-war period). Materials and methods of research: reports of research works of the Laboratory of Hygiene of Carcinogenic Factors and Nanomaterials of the SI «O.M. Marzieiev Institute for Public Health, NAMS of Ukraine» and own publications over the past 5 years. Bibliosemantic, analytical, hygienic and medical-statistical methods were used to process the materials. Results. The analysis of field and analytical studies has shown that over the past 20-25 years old, against the backdrop of a reduction in industrial emissions, the volume of use of plant protection products and plant products in agricultural activity has increased significantly, and in everyday life – household chemicals, cosmetics, etc., most of which contain specific substances – endocrine disruptors. It was shown that over the years, the rate of increase in the rate of cancer of the endocrine organs (cancer of the mammary, thyroid, prostate glands), uterine body and ovaries increases. The obtained data indicate a trend towards rejuvenation of oncological diseases of hormone-dependent organs. The danger of atmospheric air pollution in cities has been studied; a comparative assessment of carcinogenic and non-carcinogenic risk for the population in a highly industrialized city with a complex of ferrous metallurgy enterprises and a city where there are no specific sources of pollution was carried out. It was concluded that for study of environmental issues regarding the state of the air environment, it is sufficient to use hygienic indicators - maximum permissible concentrations and total pollution indicators, while for the assessment of the impact on human health, the use of risk indicators is more adequate. This raises the question of the compliance of domestic hygienic (medical and sanitary) regulations with international risk indicators. This is especially true for factors with mutagenic and carcinogenic properties. The analysis of risk indicators for a number of carcinogenic substances included in the domestic regulatory and methodological bases at the level of their maximum permissible concentrations proved that the standards for atmospheric air according to the international classification scale correspond to an acceptable risk (1 - 104) for only 26% of substances, and for air of the working area - 45% of substances. Consequently, most of the hygienic standards, both in the atmospheric air of populated areas and in the air of the working area, according to international standards, do not meet the safety requirements for the population and need to be revised using international approaches and focusing on the risk criteria for the development of neoplasms due to the action of individual compounds. Conclusions: the real air pollution in populated areas poses a certain danger to the population and requires preventive measures to reduce it. The currently existing national regulatory framework for the permissible content of carcinogenic substances in the air environment (atmospheric air and air of the working area) does not meet the requirements of the EU and the USA.

Phoenician Iron Smithing and Cult at Persian-Period Tel Akko

ABSTRACT Renewed excavations on Tel Akko have uncovered evidence of large-scale Phoenician industrial iron smithing during the Persian period (sixth–fourth centuries BCE). It is distinguished not only by the scale of production but also by the integration of ritual activities with iron smithing. This article presents evidence for an iron workers’ cult at Tel Akko—a largely unexplored aspect of Phoenician religion and cultic practices.

An Improved 2-D Subdomain Method Toward Electromagnetic-Performance Analysis of Line-Start Permanent Magnet Synchronous Motor

The 2-D subdomain method (SDM) has proven to be a time-efficient approach suited for determining the magnetic field of permanent magnet synchronous motor (PMSM). However, further application of this method into the field analysis for the line-start PMSM (LSPMSM) is limited by its natural defects including (a) inability to consider the saturation effect of iron material and (b) failure to deal with the rotor eddy currents allowing self-start. In this work, the step-by-step or iterative numerical calculation using the finite difference method (FDM) is embedded into the execution of conventional 2-D SDM, through which an enhanced version addressing all issues as stated above is obtained. The improved SDM avoids limitations of pure analytical method and possesses higher calculation efficiency than that of pure numerical method. Reliability of the presented method is validated by the finite element analysis (FEA) and tests.

Development strategy of Russian metallurgical companies in the new world economic order

Subject. The article investigates features of modern strategic development of iron and steel plants in the Russian Federation Objectives. The purpose is to determine the main directions of development strategy of the metallurgical complex in the production of ferrous and non-ferrous metals in Russia to identify further prospects for industry enterprises. Methods. The study employs methods of scientific cognition, like comparative analysis, synthesis, induction, and deduction. These methods helped to build dynamic and structural models. Results. We performed the analysis of technological innovation effectiveness in the production process of metallurgical enterprises, identified the main problems of the industry resulting from the crisis situation in the country and the world, and considered issues related to interaction of innovation activity and the use of R&D in the development of the industry. The study unveiled the specifics of the Russian metallurgical industry in the field of export, allocation of funds for the introduction of innovation. Conclusions. The development strategy of Russian metallurgical industry for the period up to 2030 set benchmarks for the growth of ferrous and non-ferrous metallurgy, however, Russian enterprises need investments in R&D, which, in the future, will entail an increase in the profitability of their products and a more stable position among international competitors in the market.

Surface nanocrystallization of pure iron achieved by anodization-reduction treatment and its effect on lower-temperature nitriding behaviors

In this work, a novel method named anodization-reduction composite treatment was designed to achieve surface nanocrystallization on pure iron materials. Subsequently, this method was employed as pretreatment for gas nitriding of pure iron and its effect was studied systematically. The experimental data illustrated that a 1.3 μm thick Fe2O3 layer with nanoporous structure was successfully fabricated by anodization treatment in solutions containing 0.1 M NH4F and 1 M H2O. After hydrogen reduction at 400 °C, the nanoporous Fe2O3 layer was transformed to pure layer with nanoparticles stacked structure. Additionally, each particle is composed of several pure iron grains with size of 2–10 nm. After lower-temperature gas nitriding at 400 °C, a dense compound layer composed of Fe3N and Fe4N phases with thickness of 3 μm was formed on surface of anodization-reduced sample. The anodization-reduced nitrided sample show the higher hardness, lower friction coefficient and improved wear resistance than those of original nitrided sample. The acceleration of nitriding process may be attributed to the increased adsorption area of nitrogen atoms, rapid diffusion effect in nanocrystalline and more nucleation sites for nitrides. This paper provides a novel surface nanocrystallization method for iron to reduce its nitriding temperature or duration.

Nine types of iron smelting furnaces in southern Siberia in the first millennium AD: A review of archaeological and chronological data

This article systematizes all currently known archaeological data and radiocarbon dates related to iron-smelting furnaces from Southern Siberia. On the basis of 159 excavated and well-preserved furnaces, nine construction types can be identified. The analysis of a series of radiocarbon dates made it possible to revise previous models about emergence and development of iron metallurgy in Southern Siberia and neighboring regions. We conclude that iron metallurgy developed in the region not in the Scythian time, as has long been assumed, but in the subsequent Xiongnu period of the 2nd century BCE – 2nd century CE. During the 3rd–6th centuries CE, metallurgy flourished, which is expressed in the different types and numerous smelting furnaces that coexisting in the same region. This article raises for the first time the problem we have called the ancient Türkic metallurgy paradox. This inexplicable phenomenon describes the sudden and almost complete disappearance of iron metallurgy in Southern Siberia in the 7th century CE.

Green synthesis of zero valent iron using tannins to activate persulfate for sulfamethoxazole degradation

Majority zero-valent iron (ZVI) materials are prepared by reducing agents in liquid phase, resulting in the high environmental pollution and poor particle size distribution uniformity. Therefore, this study employed a green synthesis method to prepare ZVI. Tannins (TA) with phenolic hydroxyl groups that are characterized by strong reducing capacity were employed to synthesize ZVI (TA@ZVI). The dispersity and stability of ZVI was improved by TA, which inhibited the agglomeration of ZVI. Meanwhile, the specific surface area of TA@ZVI was higher than chemical prepared ZVI, increasing the reactive sites. The organic matter components enriched on TA could promote the adsorption of pollutants and complex with Fe(II/III) to enhance the reactivity of TA@ZVI. Also, the polyphenol structure in TA was oxidized to quinone, which facilitated electron transport. In order further test the performance of TA@ZVI, SMX was chosen as a target pollutant to study the oxidative degradation performance of TA@ZVI. SO4•− degraded about 16.4%–25.5% SMX and •OH degraded about 49.8%–63.9% SMX in the pH range of 4–6 while •OH played a dominant role in the neutral and alkaline conditions. Moreover, the presence of TA reduced Fe(III) to Fe(II) and promoted the release of Fe(II), providing a continuous source of •OH for the oxidative degradation of SMX. Besides, the conversion of Fe(II/III) was accelerated due to TA, which delayed the formation of passivation layer. Thus, TA enhanced the antioxidant capacity of ZVI. Generally, this study provided an environmental-friendly technology to synthesize and improve the reactivity of ZVI.

Simulation of gas dynamics of oxygen flow and hydrodynamics of cooling water flow in tuyere tips with tangential optimized nozzles and results of their pilot tests.

The blowing mode largely determines the technical and economic indicators of BOF smelting, which was confirmed during the technological audit of the BOF shop of Azovstal Iron and Steel Works, carried out in 2021. It was found that the blowing mode of the process using an oxygen lance of the basic design was noticeably shifted from the optimal one in the direction of “hard” blowing. In a significant number of melts this led to an increase in the specific consumption of metal sheets, deterioration of lime assimilation by slag, dephosphorization and desulphurization of the metal. Taking into account that adjustment of the blowing mode by changing the working height of blowing and oxygen consumption did not provide a stable positive result, changes were made in the design of the tuyere tip. The design of the head with tangential arrangement of nozzles is proposed to “soften” the blowing of melts. The advantages and dis-advantages of oxygen lances of this type are considered. Numerical modeling of the gas dynamics of the oxygen flow and the hydrodynamics of the flow of cooling water in a tip with a tangential arrangement of nozzles has been per-formed. On the basis of simulation results, two variants of an improved design of the tips of 350-t LD converters with five (variant 1) and four (variant 2) main peripheral tangentially oriented nozzles and a central nozzle of lower throughput were developed to use them mainly in the second and first periods of the campaign according to the lining of the converters, respectively. It is shown that the design parameters of the nozzle blocks provide an oxygen jet outflow regime close to the design one in the main range of oxygen operating flow rates and a “non-separated” outflow regime with a decrease in the off-design ratio down to 0.8. The design parameters of the cooling system provide both an acceptable loss of water pressure in the head (0.9 MPa), the absence of local low-speed vortex zones of water, and a fairly high average coolant flow rate along the most heat-stressed (the lower) surface of the tip (about 4.5 m/s). As a result of industrial testing of a pilot batch of experimental heads with five main peripheral tangentially oriented nozzles, manufactured at the plant’s own repair and mechanical base, an increase in the resistance of copper tips was found to be 1.2 times, the resistance of lances to removal for cleaning from accretion was found to be 6.8 times, reduction in the specific consumption of metal charge by 0.9–5.6 kg/t, an increase in the dephosphorization and desulfurization coefficients of metal in the converter by 0.7–1.5 and 1.3–3.2%, respectively.

Institutionalization of ESG-principles at the international level and in the Russian Federation, their impact on ferrous metallurgy enterprises. Part 2

Currently, a new development trend is being formed in the world associated with the decarbonization of economies. This process is based on the institutionalization of ESG-principles – an approach to doing business, characterized by the involvement of companies in solving environmental, social and governance problems. The process of institutionalization of ESG-principles at the international level was initiated in 1948 with the adoption of the Universal Declaration of Human Rights under the auspices of the UN. The active involvement of Russia in the formation of the institutional framework in the field of ESG has begun only in 2020. The reason for this was the ratification of a number of international documents, as well as the active promotion of climate policy by many countries of the world. The stages of the institutionalization process at the international level discussed in detail in Report 1. The decarbonization of economies creates development risks for industries whose products are characterized by high carbon and energy intensity. Ferrous metallurgy also belongs to them. This report presents the results of a study of the effectiveness of measures taken by the Russian Government in the field of reducing atmospheric air pollution in large industrial centers of the ferrous metallurgy based on data from the Unified Information System for Monitoring Air Quality, as well as the results of an analysis of the ESG-practices of the largest Russian ferrous enterprises and compliance with carbon intensity and energy intensity of their products according to the criteria of sustainable (including green) development projects established in our country. As a result of the study, it was found that despite the use of ESG-principles in their activities, the specific emissions of CO2-equivalent of the largest iron and steel enterprises significantly exceed the criteria for sustainable (including green) development projects established by the Russian Government.

Design and Realization of a Controlled Electromagnetic Breaking System

Industrial machines with sharp moving blades are extremely dangerous to workers. These machines often rotate for some time (called the run-down time) before completely stopping due to little or no brakes. In the case where brakes are used, they are mechanical in nature and are associated with problems of wear out and frequent maintenance among others. In this paper, we proposed a mathematical model and implementation of an electromagnet and design and construction of a mechanical support frame and a controller for the electromagnetic braking system. The electromagnetic braking system works on the principle of electromagnetism. To realize the semicircular electromagnets, we coil the gauge wires several times around a ferromagnetic core material. The electromagnet was connected to a 12 V 7 Ah battery and was used to lift a load whose mass and corresponding weight were predetermined using a scale balance. The magnetic force generated was equal to the amount of maximum load it could lift. The mechanical frame, on which the electromagnets, motor, battery, switches, and chain drive system were mounted, was designed using SolidWorks and constructed by measuring, cutting, and joining of iron materials. A microcontroller and a power MOSFET were used in the control circuit to drive the electromagnet. Major results such as the realized electromagnets and the magnitude of the electromagnetic force (1.43 N) produced by the electromagnets are presented. The mechanical frame and the control circuit are also presented. The braking force was greater than the rotation torque of the disc, and hence braking was achieved.

Efficient degradation of antibiotics by heterojunction photocatalysts driving peroxydisulfate activation under visible light irradiation

Heterogeneous iron materials show potential for activating peroxydisulfate (PDS). However, these systems may be constrained by low efficiency and secondary pollution. The visible-light-assisted activation has been demonstrated as a feasible and effective approach to enhance PDS activation by iron-based materials. In this study, a visible-light-responsive Bi2WO6/Fe2O3 heterojunction photocatalyst was synthesized to improve the ability of Fe2O3 for PDS activation through an effective Fe(III)/Fe(II) cycle. Rapid tetracycline (TC, a common antibiotic) removal (91.7% within 60 min at a concentration of 20 mg·L-1) was achieved in the constructed Bi2WO6/Fe2O3/PDS/vis system under conditions of 0.3 g·L-1 PDS and 0.3 g·L-1 catalyst. The corresponding pseudo-first-order rate constant reached 4.16 × 10-2 min-1, which was 8.42 and 16.38 times higher than those of Bi2WO6/Fe2O3/vis and Bi2WO6/Fe2O3/PDS systems, respectively. Moreover, the Bi2WO6/Fe2O3 exhibited favorable stability and reusability even after five cycles. Lastly, a catalytic mechanism for TC removal and PDS activation was proposed based on quenching experiments and electron spin resonance (ESR) tests. The SO4•- and •OH played a major role in TC removal, while •O2– and 1O2 contributed as auxiliary factors. This study presents a promising strategy for activating PDS using cost-effective and stable Fe(III)-based heterojunctions, and such an idea can be used to design catalysts for other high-value reactions.

Effects of Modified Biochar-Supported Zero-Valent Iron on the Removal of Trichloroethylene and Responses of Microbial Community in Soil

Trichloroethylene is a typical organic contaminant that has widely existed in industry sites and groundwater. Biochar-supported zero-valent iron material has been used to remove trichloroethylene in groundwater; however, it could affect the microbial communities in aquifer soil, leading to changes in the environmental behavior of trichloroethylene. In this study, biochar was prepared under oxygen-limited conditions and modified by NaOH and HNO3 agents. Then, a modified biochar-supported zero-valent iron composite (BC composites) was synthesized using ball milling technology. The effects of BC composites on the removal of trichloroethylene and the responses of the microbial community were investigated under the condition of simulated aquifer soil. The results showed that the specific surface areas of BC composites were increased after the modification with NaOH. The highest removal rate of trichloroethylene was observed in the BC_2 treatment, up to 90.01%. Except in the BC_1 treatment, the diversity and abundance of soil microorganisms were increased, and the microbial community structure was changed after the addition of different BC composites, in which Bacillus, Thiobacillus, and Pseudomonas might have been the potential degrading bacteria of trichloroethylene. The abundance of Thiobacillus and Pseudomonas increased under the BC_2 treatment, which was favorable to the removal of trichloroethylene. The stabilization of the microbial community structure was probably maintained by Nocardioideas, Thermincola, Lysobacter, Gemmatimonas, Microvirga, and Pseudomonas. According to the predictive analysis of microbial metabolic pathways, the abundance of xenobiotics biodegradation and metabolism genes and the folding, sorting, and degradation of genes were the highest under the BC_2 treatment. Thus, the NaOH-modified BC composite could prompt the removal of trichloroethylene in simulated aquifer soil, probably due to the increase in the abundance of soil-degrading bacteria and the expression of degradation genes, demonstrating that the NaOH-modified BC composite could be used for the remediation of the organic-contaminated industry sites as a new composite material.

Investigation of the Effect of Additional Zirconium Diboride (ZrB2) in Spherical Graphite Cast Iron on Mechanical Properties

Steering gearbox bodies, which are produced from spheroidal graphite cast iron, experience wear and gaps over time since they operate under load. It is important to strengthen steering gearbox bodies to avoid this. In this study, a steering gearbox body was produced from a spheroidal graphite cast iron material with zirconium diboride at varying rates (0%, 0.227%, 0.455%, and 1.364%). Samples of the material were prepared according to established standards for hardness, compressive strength, and wear resistance tests. The mechanical properties of test samples with and without zirconium diboride (hardness, compressive strength, and wear resistance) were compared. Sample C showed the highest hardness measurement of 243 HB after adding 0.455% zirconium diboride. As the rate of addition increased, the values obtained from the hardness measurement test also increased. Sample C had the highest compressive value of 1438 MPa, with a 0.455% addition rate. It was found that the compressive strength values also increased as the addition rate increased. Wear tests were conducted to analyse wear volume, wear rate, and friction coefficients. A scanning electron microscope (SEM) device was utilised to identify wear mechanisms on the worn surfaces of the samples. Per the results of this study, wear volume values were found to increase with the load value.

Recovery of binary-component textile wastewater contaminated by reactive dyes through adsorption onto magnetic separable MgO nanoparticles produced from solid waste of ductile cast iron industry, process identifications, characterization and regeneration

A new magnetic separable Mg-based adsorbent was produced from a waste collected from cast ductile iron industry for removing reactive dyes from the industrial textile wastewater. The magnetic coreshells were prepared based on one step gel-combustion approach. Mg2+ ions were extracted from the gray solid waste through the acid leaching. The coreshells were added to the prepared solution under sonication, and then Mg(OH)2 particles were decorated onto magnetic nanoparticles via precipitation followed with calcination at 500 °C. The reusable adsorbent was utilized for the uptake of R Blue 222, and R Red 195 dyes from single, and binary-component effluents. The adsorption studies were conducted at a variety of dye concentrations by adding different dosage of adsorbents. The competitive adsorption studies demonstrated that the capacity for the dye uptake from the binary-component wastewaters is greater than those for single-component systems, promoting the adsorptive performance. With decoration of MgO nanoparticles over the coreshells, the growth of crystallites was limited as identified from XRD patterns. An increase in pore volume, and average pore diameter, ∼ 14 nm, are the main reasons for the promotion of active site numbers which is beneficial to prevent the efficient loss in capacity due to magnetization.

Analysis of the influence of the chemical composition and metallurgical quality of grinding balls on their operational properties

On the basis of a complex of researches carried out in laboratory and industrial conditions using standard methods of metallographic analysis and impact testing of balls, the regularities of the formation of the quality of the macro- and microstructure of grinding balls in relation to their operational resistance in the production of rail steels and specialized ball steels of various chemical compositions are determined. When studying samples of five different compositions, it was
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 determined that grinding balls made of 76XF steel have an optimal homogeneous microstructure that provides high impact resistance in combination with increased hardness after heat treatment. Additional alloying of the specified rail steel with chromium and nickel in excess of the requirements of regulatory documentation leads to the formation of dendritic liquation in the cast structure, which decreases, but is not completely eliminated after heat treatment of the produced balls. This mi-crostructure is defective and causes a reduced impact resistance of grinding balls. In the production of balls made of 90HAF grade hypereutectoid rail steel, cementite is present in the microstructure, which reduces the balls' resistance to shock loads; at the same time, there is no noticeable increase in the hardness of heat-treated balls compared to balls made of 76XF steel. With regard to balls made of specialized steels of grades Sh2.1 and Sh2.3, the determining effect on their impact resistance of macrostructure defects passing from the initial cast blanks has been established. The features of the quenching microstruc-ture of grinding balls made of specialized steels of the specified grades, formed by varying the modes of their heat treatment, does not significantly affect the impact resistance of the balls