Comparative analysis of the main occupations working conditions in the copper production by pyrometallurgical and hydrometallurgical methods in Russia

Introduction. The primary materials for copper production are sulfide copper-nickel and oxidized ores with a copper percentage of 1.5-4%, traditionally processed by the pyrometallurgical method. For processing depleted copper-containing raw materials (less than 1%), the pyrometallurgical approach is not commonly suitable. The introduced hydrometallurgical way differs by including in one production process, combined underground leaching of ore, extraction of copper from solution, and the following electrolysis. At the same time, insufficient attention is paid to the hydrometallurgical method of processing depleted copper raw materials from a hygienic standpoint in our country. Materials and methods. Based on the results of our research carried out at copper-smelting plants using pyro- and hydrometallurgical methods of processing raw materials, a comparative analysis was carried out for such indicators as the pollutants content in the workplaces’ air at different stages of production, predicted values of occupational cancer risks, toxicity indicators, and the health and essential physiological functions of workers. Results. Working under increased heat intensity in hot shops, exposure to sulfur-containing gases and industrial aerosols leads to significant changes in hemodynamics and thermoregulation stress in workers. In the hydrometallurgical production of copper, the only occupational hazard exceeding hygienic standards is sulfuric acid vapours, and changes in physiological parameters and thermoregulation are insignificant. The predicted values of occupational cancer risk for hydrometallurgical machines operators exceed the acceptable level after 9-10 years of working experience. For smelters, an unacceptable level of risk is achieved with up to 5 years of working experience. Conclusion. For the first time in the country, a hygienic assessment of the hydrometallurgical method of processing depleted copper raw materials was proved to be the only appropriate method of improving working conditions in copper production.

Optimization of Conditions for Processing of Lead–Zinc Ores Enrichment Tailings of East Kazakhstan

This article presents the results of studies of a low-waste technology for processing enrichment tailings using a combined enrichment–hydrometallurgical method. After washing the enrichment tailings from harmful products and reducing their size, multi-stage flotation of the crushed material of the enrichment tailings was carried out. The use of a new reagent in the flotation process was studied in order to ensure the maximum recovery of the main valuable components from the enrichment tailings. A new collector of Aero 7249 (Shenyang Florrea Chemicals Co., Ltd., Shenyang, China) type was used for the flotation. The recovery of valuable components was as follows: Cu, 6.78%; Zn, 91.69%; Pb, 80.81%; Au, 95.90%; Ag, 82.50%; Fe, 78.78%. Tailings of the flotation were re-enriched using a fatty acid collector (sodium oleate). Additional (reverse) flotation resulted in obtaining a product corresponding to the composition of building sand in terms of the content of valuable components of the waste rock. The studies of the conditions for processing the enrichment tailings of lead–zinc ore indicate the possibility of its optimization in order to maximize the involvement of waste in the production.

Comparative Life Cycle Assessment of Merging Recycling Methods for Spent Lithium Ion Batteries

An urgent demand for recycling spent lithium-ion batteries (LIBs) is expected in the forthcoming years due to the rapid growth of electrical vehicles (EV). To address these issues, various technologies such as the pyrometallurgical and hydrometallurgical method, as well as the newly developed in-situ roasting reduction (in-situ RR) method were proposed in recent studies. This article firstly provides a brief review on these emerging approaches. Based on the overview, a life cycle impact of these methods for recovering major component from one functional unit (FU) of 1 t spent EV LIBs was estimated. Our results showed that in-situ RR exhibited the lowest energy consumption and greenhouse gas (GHG) emissions of 4833 MJ FU−1 and 1525 kg CO2-eq FU−1, respectively, which only accounts for ~23% and ~64% of those for the hydrometallurgical method with citric acid leaching. The H2O2 production in the regeneration phase mainly contributed the overall impact for in-situ RR. The transportation distance for spent EV LIBs created a great hurdle to the reduction of the life cycle impact if the feedstock was transported by a 3.5–7.5 t lorry. We therefore suggest further optimization of the spatial distribution of the recycling facilities and reduction in the utilization of chemicals.

RECYCLING TECHNOLOGY OF ACTIVE MATERIALS OF THE ZINC-MANGANESE CURRENT SOURCES

It is being investigated whether it is possible to develop a low-cost method for processing used Zn-MnO2 primary chemical power sour­ces, which is focused on a closed cycle of ge­nerating zinc-manganese power sources from wasted batteries. It is proposed that chemical processing reagents be replaced with less dangerous ones for the environment and people, in accordance with «green chemi» principles. The existing hydrometallurgical method of processing of primary current sources with selective extraction of the spent part of the anode mass is modified and laboratory processed. The stage of additional extraction of arsenic is entered. The proposed technological scheme avoids heavy air loads in the form of carbon dioxide emissions by eliminating the stage of burning organic matter. The use of acetic acid allows to avoid sulfuric acid discharges and to obtain high-quality for secondary production of cathode mass of new chemical current sour­ces, as well as to obtain technical zinc powder and active zinc powder using hydrometallurgical technology for anode mass production of primary batteries. Also, the presence of stages of extraction of heavy metal ions (Hg2 +, Pb2 +, Cd2 +) and Arsenic to obtain products that can be further used in other technological processes makes this technology virtually waste-free, and in the stages of recovery of acetic acid and hypochlorite – closed. Thus, the use of the proposed technological schemes allows to make such production not only a little harmful to the environment, but also for workers, as well as to simplify the requirements for technological equipment.

Leaching Kinetics of Secondary Zinc Oxide in a NH3–NH4HCO3–H2O System

Secondary zinc oxide (SZO), which comes from the zinc industry, is an important secondary resource of zinc and other valuable metals. In this study, the production feasibility and rationality of a cleaner zinc recovery process using SZO and a hydrometallurgical method were described. Zinc extraction is promoted by the addition of ammonium bicarbonate to a NH3–H2O system, and the maximum recovery of zinc could be close to 80% at the optimum leaching conditions of a stirring rate of 400 rpm, an ammonia/ammonium ratio of 7:3, a total ammonia concentration of 4 mol/L, and a liquid/solid ratio of 7 mL/g for 30 min at 35 °C. The kinetics of leaching were modeled using the shrinking core model of constant-size particles, and the rate-controlling step was determined to be the diffusion through the product layer. The apparent activation energy of the reaction was estimated to be 11.04 KJ·mol−1, while the order of reaction with respect to total ammonia concentration was 1.53 and the liquid/solid ratio was 2.26. The analysis results of the initial residue and the leached residue indicated that lead was transferred from PbCl2 to PbCO3 and that ZnFe2O4 was not leached in the NH3-NH4HCO3-H2O system.

Thermodynamics of Copper Arsenious Raw Materials Dissolution in Nitric Acid

This article describes thermodynamic study of hydrometallurgical method for processing of copper arsenious gold-containing raw material. Chemical and phase composition of the material were researched. Calculations of the Gibbs energy change were conducted for possible reactions of the main minerals, present in the raw material, with nitric acid. Eh-pH diagrams and solid/liquid equilibrium distribution diagrams, which were constructed in order to confirm the possibility of obtaining the required reaction products through nitric acid leaching of the studied raw material.

Comprehensive Processing of Fine Metallurgical Dust

The processing of fine metallurgical dust by pyrometallurgical methods leads to the accumulation of impurities and deterioration in the quality of blister copper. Fine dust contains copper, zinc, lead, arsenic and iron. A hydrometallurgical method for the separation of the main components into the following products is proposed: copper-zinc residue, iron-arsenic residue, lead residue. The hydrometallurgical scheme consists of three stages of leaching: neutral and using sulfuric and nitric acids. When processing metallurgical dust according to the proposed scheme, a solution containing copper, zinc, iron and arsenic is formed, as well as a lead containing precipitate. Arsenic and iron are removed from the solution in the form of iron (III) arsenate, after which zinc and copper are precipitated. Lead in sediment is in carbonated form. The developed technology allows the extraction of: 87% copper, 88% zinc, 83% iron, 83% arsenic, 99% lead in individual products. Keywords: metallurgical dust, arsenic removal, nitric acid leaching