This article presents a study on the precipitation of copper from the cyanide leaching solutions used for gold–copper ores, both with and without the addition of a sulphidizer (Na₂S). Mathematical models were developed to summarize the effects of the pH, initial copper concentration, and Na₂S stoichiometric ratio on the precipitation process, using an experimental design based on a probabilistic–deterministic method. Varying the stoichiometric ratio of Na₂S has a minimal impact on the precipitation process. However, the presence of a sulphidizer is significant, as the precipitation process occurs at pH levels of 5 and below. The initial concentration of copper in the solution was identified as the most significant factor. At copper concentrations of 0.34% and 1.55% (pH = 3), the precipitation rates were 51.48% and 47.6%, respectively. This study also determined that the most effective method across the entire range of copper concentrations in the solution was the precipitation of copper in the form of copper cyanide hydrate (CuCN∙nH₂O) without the addition of Na₂S. At copper concentrations of 0.34% and 1.55% (pH = 3), the precipitation rates were 86.47% and 85%, respectively. The pH level was the most significant factor influencing this process, as copper deposition without Na₂S did not occur at a pH of 5. The obtained models allow us to accurately predict the influence of factors on the deposition process. Aided by the mathematical model of precipitation (without Na₂S), we selected the conditions for an enlarged experiment using 20 L of solution (Cu = 0.34%, pH = 3.2), which showed the high efficiency of the method. The calculated recovery amounted to 86%, where practical recovery was 87.2%, and divergence was ≥1.2%.

This paper examines energy-efficient and environmentally friendly methods of processing technogenic gold-bearing raw materials. The main focus is on studying the kinetics of the thiourea leaching process after the preliminary oxidative roasting of gold-bearing materials obtained from technogenic waste from a gold extraction plant. This study compares traditional roasting in an electric furnace with roasting in a chemical reactor with microwave treatment. Preliminary oxidative microwave roasting was found to achieve a higher thiourea leaching reaction rate due to better exposure of refractory gold. Compared to traditional oxidative heating, roasting in a microwave-assisted chemical reactor reduces processing time and energy consumption while improving the degree of preparation of the raw materials for subsequent gold leaching and increasing gold recovery by 17.8%. This reduction in activation energy is due to preliminary oxidative roasting with microwave treatment (P 1.1 kW, frequency 2.45 GHz, 700 °C for 10 min), which results in an energy reduction of 14.716 kJ/mol versus 22.630 kJ/mol for traditional oxidative roasting in an electric furnace (750 °C for 60 min).

Although the mineralogical form of occurrence of critical metals is widely recognised as a key factor controlling their recovery during beneficiation, this relationship has rarely been verified directly on freshly mined ore and its primary beneficiation products from Central Asian polymetallic deposits. This raises the research question of how the mineralogical mode of occurrence of Bi, In, Cd, Co, Se, Te and Re governs their distribution between gravity and flotation products. Accordingly, the aim of this study was to establish how the mineralogical form of occurrence of these critical metals determines their distribution among gravity-concentration and flotation products, using ores from the Zhuantobe and Strezhanskoe deposits (Kazakhstan) as a case study. To this end, the mineralogical features and distribution patterns of critical metals during gravity and flotation beneficiation of polymetallic ores from these deposits were investigated by optical microscopy, X-ray diffraction, and SEM-EDS, while metal distribution among beneficiation products was determined by chemical analysis. Sphalerite, galena, pyrrhotite, and silver tellurides were identified as the main carriers of the critical metals, with bismuth occurring as an isomorphic admixture in sphalerite (3.69 wt.%) and galena (1.85 wt.%). During flotation, distribution was governed by mineralogical affinity: cadmium and indium were preferentially concentrated in the zinc concentrate (56.31% and 15.44% recovery, respectively), bismuth in the copper–lead concentrate (23.03%), and selenium and rhenium in the copper-bearing products (23.60% and 37.05%). Correlation analysis of the gravity-concentration products confirmed a close association of cadmium with sphalerite (R² = 0.9998), bismuth with galena and sphalerite (R² = 0.9674), and cobalt with iron-bearing sulfides (R² = 0.9144). These results demonstrate that the distribution of critical metals is governed primarily by their mineralogical form of occurrence rather than by bulk ore content, providing a basis for technologies for the complex processing of polymetallic ores.

The processing of gold-copper ores with high copper and gold content embedded in sulfide minerals using cyanide solutions is associated with a number of difficulties. Copper, when reacting with cyanide, causes its increased consumption, and the embedding of gold in sulfide minerals causes gold losses with tailings. Therefore, selecting the optimal leaching conditions is necessary for the rational use of reagents, which leads to a reduction in the cost of hydrometallurgical processes for cyanide leaching of gold-copper ores and a reduction in environmental risks. The paper investigates the possibility of processing gold-copper ore with a high copper content and gold incorporated into sulfide minerals (pyrite, chalcopyrite). The aim of the work is to establish the optimal parameters for cyanide leaching by conducting tests in bottle agitators. As a result of the experiments, it was found that as the degree of ore grinding increases, gold extraction increases and cyanide consumption decreases slightly. The addition of coal during leaching significantly increases gold recovery, up to 7 %. It was noted that high sodium cyanide consumption cannot be reduced without a significant decrease in gold recovery. Au ≈ 20 % reduction in sodium cyanide consumption also reduces gold recovery by ≈ 20 %. A laboratory-industrial experiment showed that after 16 hours of ore leaching, 85.8% of the gold is transferred into solution, and after 18 hours, 86.7 %. Further prolongation of the process does not increase the gold recovery rate. Keywords: gold-copper ore, optimal parameters, cyanide leaching, gold, copper.

The growing demand for critical metals associated with the global energy transition has increased interest in their potential recovery as by-products of copper processing. This study investigates critical- and associated-element deportment in ores and flotation products from three Kazakhstan deposits representing contrasting ore-system types: the Aktogay and Bozshakol porphyry Cu–Mo deposits and the Severny Samombet Cu-skarn deposit. Bulk geochemistry, optical mineralogy, SEM–EDS observations, and technological mass-balance data were integrated to evaluate mineralogical associations and element recovery into Cu and Mo flotation products. The two porphyry systems show comparatively selective deportment: Re preferentially reports to the Mo concentrates, with recoveries of 4.05% at Aktogay and 19.03% at Bozshakol, whereas Se preferentially reports to the Cu concentrates, reaching 55.35% and 27.18%, respectively. SEM–EDS observations of Aktogay molybdenite provide mineral-scale compositional evidence for Re-bearing molybdenite. In contrast, the Severny Samombet Cu concentrate shows broader multi-element recovery, particularly for Ag (86.00%), In (74.82%), Zn (68.15%), and Cd (55.04%), accompanied by intermediate recovery of Pb, Co, and Bi. Mineralogical observations reveal a heterogeneous sulfide assemblage together with discrete Bi–Pb- and Ag–Te-bearing accessory phases. Ge shows consistently low recovery into the investigated concentrates, including only 1.31% into the Severny Samombet Cu concentrate, indicating that bulk enrichment does not necessarily translate into flotation recovery. These results demonstrate contrasting critical-element deportment patterns among the three investigated deposits and show that evaluation of potential by-products requires integration of mineralogical characteristics with quantitative flotation-product recoveries. The results provide a basis for identifying technological streams warranting further assessment for critical-metal recovery, while quantitative determination of trace-element partitioning among individual mineral hosts requires mineral-specific analytical methods.

Copper in such gold-copper ores is both a valuable component and a detrimental impurity that complicates the processing of gold by cyanidation. As cyanidation is the primary process in gold recovery technology, ores or concentrates that for one reason or another are difficult to cyanide are classified as difficult to enrich. The degree of resistance of gold ores to cyanidation is determined by a number of factors that relate to the combination of gold particles with minerals and rocks, as well as natural minerals and natural substances that retard gold dissolution and increase cyanide uptake, and permanent sorbents in the ore. These resistances may include physical and chemical suppression as well as sorption activity of minerals present in the ore. Thus, the stage of determining the material composition and characterization of gold-copper ores is important, as the further strategy for selecting a cyanide leaching technology depends on it. As a result of the conducted research it was found out that in the composition of the ore gold content in the sample amounted to – 1.2 g/t. Silver content also amounted to – 1.2g/t. The total amount of copper amounted to 0.15%. The iron content amounted to 5.10 %. The total amount of sulfur was 0.34%. Keywords: gold-copper ore, primary ore minerals, pyrite, rational analysis, cyanidation.