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%.

In this study, we investigate the potential of using acrylonitrile–butadiene–styrene flame-retardant (ABS FR) plastic obtained from electronic waste to create a new composite material through the addition of fly ash microspheres obtained from the combustion of thermal coal at Ekibastuzskaya GRES 1, with the resulting material being suitable for the manufacturing of housings and other elements of electronic equipment. For this purpose, five composite compositions with microsphere/plastic ratios of 10/90, 20/80, 30/70, 40/60, and 50/50 were developed, which were then processed in an extruder at 250 °C to obtain test specimens. The thermal and mechanical properties of the specimens were compared with a control sample developed using ABS FR plastic from electronic waste without the addition of microspheres. The obtained materials, up to a microsphere/plastic ratio of 20/80, demonstrate increased mechanical properties and thermal stability with a simultaneous decrease in material density, while a further increase in the concentration of microspheres leads to a gradual decrease in mechanical properties. These properties make it possible to use the obtained composite for producing housings and other elements of electronic equipment.

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).