The relevance of replacing the slime–H₂SO₄–H₂O system used for processing slimes from secondary copper electrolytic refining (SCER) with a slime–NH₃·H₂O–(NH₄)₂SO₄–H₂O system has been substantiated. Comprehensive studies of the characteristics of SCER slime samples were conducted. It was found that about 90 % of the copper is distributed between the Cu₂O phase and other phases, with a total copper content of 55.12 %. A new phase, Cu₄(OH)₆SO₄, corresponding to the mineral brochantite, was discovered, with a content in the slime of 6.40 %. Silver, with a concentration of 2.43 % in the slime, is present in metallic form at 69.1 %, with the remainder in the form of AgCl. The contents of associated components PbSO₄, BaSO₄, and SnO₂ are 13.52 %, 9.33 %, and 4.73 %, respectively. To substantiate the feasibility of low-temperature hydrometallurgical opening of the slime components and the conditions necessary for its implementation, determined by the specific qualitative and quantitative compositions of the slime, a thermodynamic analysis of the slime–NH₃·H₂O–(NH₄)₂SO₄–H₂O system was performed. This analysis allowed for the discovery and mathematical description of the dependencies of copper leaching indicators on the composition of the ammonia-ammonium mixture (ammonia buffer). A nomogram for the theoretical calculation of the minimum excess NH₃·H₂O/NH₄⁺ over the stoichiometrically necessary amount required for the complete formation of the copper ammine complex was constructed according to the equilibrium ammonia-ammonium solution's pH and copper concentration. Thermodynamic calculations determined the optimal composition and consumption of ammonia-ammonium solutions, as well as the characteristics of the leach pulp, such as the concentration of [Cu(NH₃)₄]²⁺ and the redox potential. Technological studies demonstrated the possibility of effective and selective extraction of copper from SCER slimes at a rate of no less than 99 % in the slime–NH₃·H₂O–(NH₄)₂SO₄–H₂O system, which was confirmed experimentally. Studies of the kinetics of copper leaching from slime in the slime–NH₃·H₂O–(NH₄)₂SO₄–H₂O system were conducted. The activation energy of the ammonia-ammonium copper leaching process from SCER slime (E_a = 5±0.25 kJ/mol) was determined within the temperature range from 15 to 45 °C at a total buffer system concentration [NH₃·H₂O] + [NH₄⁺] of 1 and 2 mol/L, as well as the order of reaction at a temperature of 24±1 °C, which is 0.24±0.02 and 0.91±0.05 for [NH₃·H₂O] + [NH₄⁺] concentrations above 1.5 mol/L and below 1.5 mol/L, respectively. A change in the kinetic mode of leaching with the limitation of the reaction rate by adsorption of reagents on the surface of solid particles to diffusion was detected when the total buffer system concentration [NH₃·H₂O] + [NH₄⁺] was reduced below 1.5 mol/L. The equation for the formal kinetics of the investigated process in the slime–NH₃·H₂O–(NH₄)₂SO₄–H₂O system was determined.

A significant portion of the world’s reserves of Ni-containing raw materials (40–66 %) is concentrated in oxidized nickel ores. One of the alternatives to the high-cost pyrometallurgical and ammonia-carbonate methods for processing such ores could be the chlorammonium recovery of nickel from relatively low-grade ores. The halide-ammonia decomposition and recovery technology of nickel from oxidized nickel ores, supplemented by a sorption process, is less stage-intensive and simpler in practical implementation. Nickel adsorption recovery is feasible using carbon sorbents that exhibit high chemical stability, withstand high-temperature exposure, and strong acidic treatment. Sorbents were obtained through steam-gas activation of extracted carbonizates from fossil coals. The sorption capacity for Ni(II) ions was studied, and the patterns and characteristic parameters of the process on carbon sorbents were identified using adsorption isotherms while varying experimental conditions. The experimental results were processed using the Freundlich and Langmuir equations. The sorbents have several distinctive features determined by their predominant microporous structure and multifunctional surface with active complex-forming atomic groups, characteristic of ampholytes with cation- and anion-exchange properties. The adsorption process is described by a pseudo-first-order equation with rate constants ranging from 0.204 to 0.287 s^–1. For the adsorption recovery of Ni(II), a scheme with two adsorbers and a pseudo-fluidized sorbent bed is proposed. Nickel desorption and sorbent regeneration were carried out with a 2.3 % sulfuric acid solution, desorbing 95 to 98 % of nickel. Standard chemical machinery and equipment are recommended for these processes. 

The article explores the possibility of obtaining lithium carbonate from the black mass – an intermediate product of lithium-ion batteries recycling. X-ray phase analysis and inductively coupled plasma atomic emission spectrometry of the black mass revealed that it contains 3 % lithium. It has been established that during water leaching, 40 % to 70 % of lithium can be selectively extracted from the black mass into the aqueous phase at L/S ratios ranging from 10 to 200. During water leaching, kinetic curves were recorded at temperatures of 25 °C and 80 °C. To remove Al ions from the leaching solution, we studied the sorption of aluminate ions on weaky basic (AN-31, CRB05) and strongly basic (A500) anion exchangers under static conditions using a model Li–Al solution. It was demonstrated that in an alkaline environment, strongly basic anion exchangers with quaternary amino groups are not able to adsorb Al ions, while AN-31 and CRB05 with hydroxyl clusters in their functional groups have a capacity of 2 to 3 g/dm³ in terms of aluminum ions. The sorption of aluminum from the model Li–Al solution was conducted under dynamic conditions using the CRB05 anion exchanger (N-methylglucamine) at specific flow rates of 2 and 4 column volumes per hour. Elution sorption curves were plotted, and both the dynamic exchange capacity and the total dynamic exchange capacity were determined. Additionally, we showed that aluminum ions can be removed by sorption so that their residual concentration in the raffinate drops below 0.5 mg/dm³. Sorption purification of the solution after water leaching of the black mass was performed using a weaky basic anion exchanger Diaion CRB05 and a chelate cation exchanger Purolite S950. After evaporation of the purified solution, we obtained lithium carbonate with a main substance content of 98.2 %.

This paper presents the results of theoretical and experimental studies on the process of gold adsorption from cyanide solutions onto activated carbon (AC). One of the objectives of the study was to identify the functional relationship between the mass loading of AC in the volume of the adsorption column solution and the kinetics of the process. To achieve this, a modified adsorption kinetics equation (considering the heterogeneity of the process) was proposed, which incorporates the solid phase of the carbon sorbent in the unit volume of solution as a third intermediate agent of adsorption interaction between the adsorbate ions and the free active sites of the AC. As a result, a modified third-order adsorption kinetics equation for gold adsorption on AC was derived, taking into account the solid phase loading of AC in the solution volume, along with its analytical solutions under conditions of constant gold content in the initial solution and the process conducted in a closed volume with varying gold concentrations in the solution according to the material balance equation. The relationship between the solutions of the kinetic equation and the adsorption isotherm equation was established. From the solutions of the kinetic equation, a modified Langmuir isotherm equation was derived, which allows determining the equilibrium concentrations of gold on the AC and in the solution a priori under the condition that the process is conducted in a closed volume, with known initial gold contents in the solution and on the AC, as well as with a known AC loading in the adsorber volume. The theoretical dependencies of the adsorption and desorption rate constants on temperature, convective, and diffusion parameters are discussed. The presented mathematical model of adsorption kinetics is valid under the conditions of gold adsorption on AC from gold cyanide solutions with an adsorption time of up to 2 days and a sorbent capacity utilization degree of 40–60%.

The paper investigates the extraction of rare earth elements (REE) from technogenic sources – phosphogypsum and uranium in situ leaching (ISL) solutions. We found that mechanical activation significantly increases the degree of REE leaching from phosphogypsum. We also obtained data on sorption leaching of REEs from phosphogypsum. It has been shown that, depending on the ion exchanger used and its form, chemical activation can double the leaching degree of the target components. The paper presents the findings of the study on the sorption recovery of scandium from uranium in situ leaching solutions. We determined that Sc sorption from uranium ISL solutions on the Purolite S-957 cation exchanger is much more effective than on Lewatit TP-260, Purolite S-950, Tulsion CH-93 CH-93, and ECO-10 ampholites. However, it should be pointed out that none of the listed sorbents is highly selective towards scandium ions. The paper presents comparative data on Sc extraction from uranium ISL solutions using Lewatit VP OC-1026 and Axion 22 commercial solid extractants synthesized according to the method described in the paper. We determined the mechanism of scandium extraction from uranium ISL solutions using Axion-22 and proved that it shows high selectivity towards scandium ions. Studies on the desorption of scandium from the saturated solid extractant showed that the most effective desorption agent is an aqueous solution of hydrofluoric acid. Additionally, the paper investigates the sorption extraction of REEs from uranium ISL solutions on cation exchangers KU-2, KM-2P, and KF-11. We found that the best eluents for the desorption of REEs from the saturated cation exchanger are solutions of calcium chloride and ammonium nitrate. It has been shown that the concentration of REEs in the solution and the removal of major impurities (Fe and Al) are quite effective when REEs precipitate from the desorption solution by fractional hydrolysis. The paper describes the separation of La, Nd, and Sm by elution from the saturated impregnate containing phosphorylpodande and Di(2-ethylhexyl) phosphoric acid in its structure. It should also be noted that ionic liquids can be useful for the extraction of REEs from the solutions of various electrolytes. We presented one of the technological schemes illustrating REE extraction from phosphogypsum.

An analysis was performed on the temperature, rate and force parameters of the hot cladding process for the experimental Al–2%Cu–2%Mn alloy with technically pure aluminum grade 1050A, as well as on the stress-strain state of the metal in the deformation zone at reductions of 30, 40, and 50 %. Plastometric tests were conducted within the temperature range of 350–450 °C, strain rates of 0.1–20 s^–1, and true strain of 0.1–0.9, and coefficients for calculating the flow stress of the experimental alloy were determined. The thermal conductivity of the Al–2%Cu–2%Mn alloy under hot deformation conditions at temperatures of 350, 400, and 450 °C was theoretically calculated to be 161, 159, and 151 W/(m·K), respectively. The study of the cladding process on a two-high rolling mill was carried out using the QForm finite element simulation software. It was found that when the metal of the cladding layer comes into contact with the roll, its temperature decreases by approximately 100 °C, with the temperature across the height of the composite equalizing within 20–30 ms after exiting the deformation zone. The rolling force is evenly distributed between the two rolls in all cases considered, while the rolling torque on the roll on the cladding layer side is half that on the roll contacting the base layer, which is characteristic of asymmetric rolling. Points characterized by optimal bonding conditions of the rolled layers were identified, located at 10 % and 70 % of the deformation zone length along the rolling axis, where normal stresses significantly prevail over shear stresses. It was determined that the formation of these areas is due to the nature of plastic flow, including the presence of a non-deforming hard layer and a sticking zone.

High-entropy coatings are highly promising for protecting steel parts in coastal and marine infrastructure from corrosion and tribocorrosion. This study examines the properties of medium- and high-entropy Fe–Co–Cr–Ni–(Cu) coatings produced by vacuum electrospark deposition. The coatings, with thicknesses of up to 30 μm and varying copper content, exhibit a single-phase solid solution structure with an FCC lattice and a dense, homogeneous morphology. The addition of 14 at.% Cu was found to enhance corrosion resistance, shifting the corrosion potential to 100 mV. In friction conditions within artificial seawater, the inclusion of copper also improved tribocorrosion properties, raising the corrosion potential during friction to –165 mV. This improvement is attributed to the galvanic deposition of dissolved copper on the worn areas of the coating, which also reduces the friction coefficient from 0.37 to 0.26. The Fe–Co–Cr–Ni–(Cu) coatings demonstrate high wear resistance, ranging from 5.6 to 9.6·10^–6 mm³/(N·m). The findings confirm the potential of these coatings for applications in environments subject to both friction and corrosion.