Materials Science Forum Vol. 946

Abstract: The direct reduction of metals from a complex oxide with low iron content by solid carbon and indirect reduction by CO gas were studied in a vertical laboratory resistance furnace at 1300 °C for an hour reduction time. The experimental results were described from the point of view of the electrochemical nature of the metal reduction process, that involves the interaction of ions and electrons in the oxide lattice. The technique was developed by using the two different software programs for the quantitative estimation of the areas, average size and number of the metal forming in a complex oxide with extensive fields of vision. The obtained results of the quantitative characteristics of the metal forming during solid-phase carbo-thermal reduction were presented. The processes of reduction by solid carbon and CO gas based on the areas occupied by metal particles were quantitatively compared. The experimental results and the prospects for further experimental work were assessed and outlined.

Abstract: Currently, about 80% of all industrial chemical reactions are carried out with the help of catalysts or depend on catalytic processes. In this case, catalysts containing platinum group metals (hereinafter - PGM) occupy a special position, due to their high catalytic activity and selectivity. A significant part of the net global demand for PGM is for the production of catalysts, accounting for approximately 45% for platinum, 30% for palladium, 92% for rhodium, 35% for ruthenium, 15% for iridium. The most important condition for the economical use of catalysts containing precious metals is their efficient recycling, which will be discussed below.

Abstract: This article describes a method for the hydrochemical dissolution of a sulfide gold-bearing raw material from the Uderey’s deposit using nitric acid. The chemical and phase compositions of the studied material, mainly represented by compounds of silicon, sodium, arsenic, iron and sulfur, are investigated. Phase composition: pyrite, arsenopyrite, quartz, thenardite. The dependences of the influence of temperature, time, and the liquid to solid ratio on extracting the main components in the solution were determined by methods of mathematical experiment planning. The calculated values ​​of the determination coefficients testify to the adequacy of the chosen two-level model. The optimum parameters of the process were obtained: L/S ratio = 8; the nitric acid concentration was 6 M; experiment duration was 75 minutes.

Abstract: This article covers acid nitric leaching of Olympiada deposit refractory gold-bearing concentrate after alkaline leaching of stibnite. Thermodynamic analysis of the reaction pyrite and arsenopyrite with nitric acid chemical equations was performed. Equilibrium Eh-pH Pourbaix diagrams of heterogeneous systems studied, containing iron and arsenic were charted. Investigation of elemental and species analyses was maintained. The analysis of the main elements distribution and their combining over grains with the help of electron-probe microanalysis (EPMA) was investigated. It is established, that the material mainly consists of compounds of quartz, dolomite and calcite, as well as pyrite and arsenopyrite. Pre-treatment decarbonization operation of the feed material was proposed with the aim to reduce nitric acid consumption. The dependences of effects of the nitric acid concentration and L/S ratio on iron and arsenic dissolving were determined.

Abstract: Copper dross are produced by rough decopperizing of blast furnace lead bullion. During liquation separation of copper dross from lead bullion most of arsenic and copper are concentrated in copper dross, arsenic content is approximately 4% As. Currently the processes for arsenic recovery from copper dross are understudied. In this work the focus is given to studying kinetics of the process for recovering arsenic from copper dross by alkaline-sulfide leaching. Alkaline sulfide leaching allows carrying out selective removal of arsenic into solution, keeping at this non-ferrous and precious metals in leaching residue. The studied method of alkaline sulfide leaching of copper dross provides backgrounds for developing technology that would allow processing of copper dross with selective arsenic removal from lead production cycle. By minimizing circulation of this harmful impurity in lead production it is possible to lessen destructive effect of its aggressive compounds on smelting-units refractory. Kinetics of alkaline sulfide leaching of copper dross was understudied up to date. This work is an attempt to fill the gap.

Abstract: In aluminium preparation by means of electrolysis of alumina-cryolite melts one of the largest-scale type of industrial waste is spent pot lining (SPL). Chemical composition of SPL carbon part consists of various elements with fluorine as the main one. One of the solutions of the problem of reducing environmental load by means of storage of waste of this type is extraction of valuable components (such as fluorine), that can be used further for preparation of fluorine entities (cryolite, calcium fluoride), that are brought back to electrolytic process. We have held experiments on extracting fluorine from SPL by caustic liquor leaching under effect of ultrasonic oscillations on a pulp, increasing the degree of fluorine solubilization. By means of mathematical planning method of a factor experiment cross impact of three leaching parameters was stated, maximum concentration of fluorine ions in the solution (20.21 gr/dm³) was achieved in following conditions: NaOH concentration - 2%, solid-liquid ration - 6:1, process length - 90 min. The degree of fluorine extraction from SPL is 69.87%.

Abstract: The article is devoted to the development of an efficient technology for the processing of aged tailings of the «Solton-Sary» enrichment plant in Kyrgyzstan. Based on the detailed investigation of initial material, authors select most appropriate technology for processing of technogenic material, considering through gravity separation, flotation and hydrometallurgical methods of processing. The methods of sequential gravity separation/flotation scheme of enrichment and direct cyanidation of initial ore at different regimes are analyzed; advantages of aged tailings agitation leaching are established. Research, presented in the article, could be useful for enrichment plants, which are developing technologies of the waste products processing in order to increase the raw material base.

Abstract: The article reviews the need to involve poor raw materials in processing, presents the results of the information search on the processing of technogenic wastes from beneficiation. It is shown which factors influence the choice of a specific flowsheet. The review of processing technologies for poor refractory raw materials was performed. The basic trends in processing of technogenic wastes from polymetallic ores beneficiation were established. It is noted that it is more advantageous to use combined hydrometallurgical methods for processing of technogenic wastes from beneficiation.

Abstract: When bauxites from the Middle Timan and Severouralsk deposits are processed into alumina by the low-temperature sintered process the high-iron content red mud can be obtained. The red mud contain up to 58 % of iron and are a potential raw material for ferrous metallurgy. Rare earth elements (REEs) such as Sc, Y and La are converted from bauxites to red mud in the form of hydroxides during processing and are easily leached by weak acid solutions. In this work, the red mud is treated with a solution of sulfuric acid (pH = 2.5–5), the REEs pass into solution, and then the solution is neutralized to obtain a precipitate, i.e. a concentrate of rare elements. The recovery of REEs is about 75–90 % (Sc, Y, La). The high-iron content red mud is converted to the naturally-doped cast iron and titanium slag (up to 50 wt.% TiO₂). As a result of processing bauxite, alumina (Al₂O₃), the naturally-doped cast iron, concentrate of REEs (Sc, Y, La, etc.) and titanium slag (TiO₂) are obtained. The flowsheet of the proposed complete processing of the high-iron content red mud is given.

Abstract: The cathode sediments (CS), obtained as a result of industrial processing of gold-polymetallic raw material with complex chemical and mineral composition, contain a significant amount of impurity metals (copper, lead, zinc, iron, etc.), which leads to a significant increase in the cost of subsequent refining of these materials. The authors carried out experimental work on preliminary acid treatment of CS for the purpose of leaching impurities and increasing the share of precious metals in them. The objects of research were cathodic sediments (bypass solutions of the enterprise) containing copper and lead in the amount,% wt., respectively: 21.29 and 4.11. We tested nitric acid as a solvent in laboratory tests. For the selection of optimal leaching parameters, studies were carried out at various concentrations of the agent (from 50 to 350 kg/m3) and the ratio of L:S - (3-7):1. The duration of the experiments was 2 h, the experiments were carried out with vigorous stirring and standard ambient temperature (25°C). The experimental data processing was carried out with the help of STATISTICA 6.0 software; As factors of variation, we chose: concentration of acid, ratio of liquid and solid phases. It has been determined that nitric acid provides effective purification of CS from impurities. After the chemical enrichment, the content of precious metals in leaching cakes increased, the CS became compliant with the requirements of TU 117-2-3-78. When processing cathode sediments with nitric acid, 99% of silver passes into solution, which then allows it to be recovered from solutions by cementation and, consequently, to obtain alloys of gold and silver separately.