The process of zinc sulfate solution purification determines process, economic and environmental production results. Since recently there has been a constant increase in the content of halides in pregnant solutions of zinc production due to the processing of technogenic zinc-containing raw materials, it is relevant to search for methods for removing halides, in particular fluorine, from zinc solutions using a variety of materials. The purpose of this paper was to investigate the effectiveness of akaganeite as an sorbent for fluoride ion removal from zinc sulfate solutions. When using akaganeite, it is especially important to choose a carrier for the sorbent since the nanosized particles of akaganeite make it difficult to clean the solution from the sorbent. Most suitable carriers for this purpose in terms of surface characteristics and physicochemical properties are gypsum and red mud of alumina production. Experiments used a zinc sulfate solution (100 g/dm³ Zn²⁺, pH = 4.5) containing 26.8–111.4 mg/dm³ F–. The maximum fluoride ion capacity was shown by red mud due to the formation of F–Al complexes. The highest fluorine recovery was demonstrated by red mud with impregnated akaganeite at elevated temperature that facilitates showing akaganeite properties and accelerates the surface ОН– ↔ F– exchange process. The gypsum-based adsorbent successfully removed fluorine due to calcium ions released and calcium fluoride formed. The amount of fluorine removed depends on the sorbent material, its consumption, sorption duration and temperature. The optimal processing conditions were (at pH = 5.5): temperature – 60 °C, process duration – 120 min, composite sorbent consumption – 20÷30 g/dm³. It was shown that composite sorbents based on red mud or gypsum with impregnated akaganeite (β-FeOOH) are most suitable for cleaning zinc solutions from halides. These adsorbents make it possible to achieve the greatest capacity and degree of fluoride ion removal (up to 98–99 %) in the actual pH range of process solutions. The abovementioned sorbents can be regenerated in an alkali solution, and then reused (up to 3–4 cycles).

Significant reserves of oxidized nickel ores are concentrated in the Ural region, in the deposits of various sizes that are mined by open-pit method. Ore is rather loose, which makes the cost of production relatively low. At the same time, the technologies employed at Ural nickel plants fail to meet the energy conservation requirements, and they are environmentally unfriendly and unprofitable. The paper proposes a two-stage hydrometallurgical technology for processing oxidized nickel ores from the Serovsky deposit. The composition of investigated ore is, wt.%: 1.01 Ni, 0.031 Co, 15.32 Fe_total, 8.51 Al₂O₃, 21.76 MgO, 43.97 SiO₂. The phase composition of the sample was determined by powder diffraction on the XRD-7000 X-ray diffractometer (Shimadzu, Japan). Serpentine Mg₆[Ni, Si₄O₁₀](OH)₈ and nimite (Ni, Mg, Al)₆(Si, Al)₄О₁₀(OH)₈ were identified as the main nickel-containing minerals. Nickel enters the crystal lattice of silicates and replaces magnesium and iron isomorphically, which significantly complicates the disintegration of such minerals by the hydrometallurgical method. The paper provides the results of laboratory studies into atmospheric ore leaching with hydrochloric acid at the first stage and autoclave leaching of the obtained slurry at the second stage depending on temperature, leaching time and acid consumption. The total (in two stages) extraction into the solution was, wt.%: 82 Ni, 73.6 Co, 22 Fe, 22 Mg, 50.4 Al. Hydrochloric acid is almost completely consumed under these conditions with residual acid concentration of about 3 g/dm³. The autoclave slurry has good filterability. Cake composition after autoclave leaching is as follows, wt.%: 0.35 Ni, 0.01 Co, 12 Fe_total, 10.63 Mg, 1.2 Al, 55 SiO₂.

A thermodynamic study of zinc sulfide high temperature oxidation leaching was conducted. Several processes can run simultaneously while metal sulfides are dissolved by oxidants in acidic solutions. Thermodynamic calculations were made using stoichiometric equations with equal oxidant consumption in order to identify the proportion of potential reactions. Moreover, stoichiometric coefficients were chosen in such a way as to reagents could exchange 1 mole of electric charge. This approach ensures a comparison of different oxidants in terms of their effectiveness in sulfides leaching. Thermodynamic analysis results obtained agree with experimental data confirming that oxidizing reactions with the formation of sulfur and sulfate ions prevail in zinc sulfide dissolution in sulfuric acid solutions under the oxygen effect. The effect of oxygen consumption and initial sulfuric acid concentration on the proportion of these reactions and equilibrium concentration of zinc cations in the solution was studied. Thermodynamic analysis showed that if the acid concentration is insufficient and limits the maximum progress of zinc sulfide oxidation with sulfur formation, oxygen is also consumed for the oxidation reaction with the formation of sulfate ions spending oxygen less effective due to 4 times less zinc cations passing to the solution. Thermodynamic calculations made it possible to find out the optimal proportions of oxygen consumption and initial sulfuric acid concentration to achieve the maximum zinc equilibrium concentration in the solution with more effective oxidant consumption without any labor-intensive experiments. The equilibrium concentration of zinc cations in the solution is in direct proportion to the initial acid concentration, and zinc cation formation is in direct proportion to oxygen consumption at the optimal acid concentration.

The article focuses on the effect of sodium lignosulfonate (LS), anionic surfactants (sodium dodecylsulfate (SDS), sodium dodecylbenzene sulfonate (SDBS)), and their mixtures on the rate of copper cementation by zinc. The results obtained demonstrate a decrease in copper cementation rate with the increasing LS and SDBS concentrations. There was also excessive zinc consumption for copper ion cementation noted due to LS and SDBS anion adsorption on positively charged zinc cathodic areas of the cementing agent and the precipitate. This led to a decrease in the rate of copper particle nucleation, energy consumption for forming new copper nucleation centers, and conditions for hydrogen overpotential reduction. In addition, rising temperature led to a decrease in zinc consumption in the presence of LS. Surfactants under investigation may be ranked by the negative impact on copper ion cementation in an ascending order as follows: SDS < SDBS < LS. LS + SDS mixture testing showed its irregular effect on copper cementation rate at test temperatures. Experiments with LS and SDBS mixtures demonstrated a linear decrease in copper ion cementation rate with increasing SDBS concentration and simultaneously rising zinc consumption. Due to the negative impact of investigated reagents discovered, we proposed a method for removing organic impurities from solutions using multilayered aluminosilicates modified by cationic surfactants. The results obtained indicate the high effectiveness of organic impurity removal from solutions providing for a 50 % increase in cementation rate in the presence of LS + SDBS mixture together with a decrease in zinc consumption.

The study covers kinetic features of gold cementation from cyanide solutions using two zinc powders of various origins. The first one was obtained by distillation and is currently applied in gold cementation from cyanide solutions (traditional powder). The second one was obtained by electrochemical reduction from the alkaline solution (experimental, electrolytic powder). The main distinguishing feature of these cementation powders is their specific surface area. This indicator for the electrolytic powder is 2.6 times higher than for the traditional one (3.02 m² /g and 1.16 m² /g, respectively) due to its dendritic form. The studies used a solution with a gold content of 50.8 μmol/dm³ and a sodium cyanide content of 0.04 mol/dm³ NaCN was taken. Cementation revealed a powder depassivation period associated with oxide film dissolution and overcoming diffusion difficulties. The traditional powder depassivation period (10–15 sec) exceeds that of the electrolytic powder (5–8 sec). Experimental rate constants of the cementation reaction were determined for the process involving both powders under study at different ratios of zinc and gold masses in the solution. Experimental reaction rate constants for the electrolytic powder under the studied conditions were 1.3– 1.6 times higher than that for the traditional powder. It was found that oxidation rates of zinc powders compared at different ratios of zinc and gold masses are virtually the same. At the same time, absolute rates of electrolytic powder dissolution in the initial period are nearly 2 times greater. As the powder reacts with the alkaline solution, absolute dissolution rates of electrolytic and traditional powders are equalized.

The paper considers the use of both traditional powdered carbon materials (graphite, soot, charcoal, shungite) and new carbon nanomaterials (nanodiamonds, fullerene, nanotubes, graphene) as a dispersed reinforcing phase in aluminum matrix composites (AMCs), and as reagents for the synthesis of titanium carbide (TiC) reinforcing particles in AMCs. It is observed that the key area of AMC development for significant improvement of their mechanical properties is the transition from micron-sized reinforcing particles to nanoparticles, and that the use of new carbon nanomaterials can play a decisive role in this. The technologies for producing such AMCs must provide the appropriate parameters of nanoparticles, their uniform distribution in the matrix and a strong adhesive interfacial bond with the matrix. However, it is highly difficult to meet these process requirements since carbon and titanium carbide nanoparticles are not wetted with aluminum at temperatures below 1000 °C and are prone to nanoparticle agglomeration due to interparticle adhesive forces that increase dramatically with the decreasing particle size. The paper provides an overview of advancements and unresolved issues in the use of powdered carbon forms in various solid-phase and liquid-phase methods of AMC production using various techniques to address these process challenges. It is shown that there is still a potential for using traditional carbon materials as well. Considerable attention is paid to the self-propagating high-temperature synthesis (SHS) of titanium carbide reinforcing particles with various carbon materials used to obtain aluminum matrix composites.

Currently, the most prospective industry development areas are prototyping and additive manufacturing. In contrast to more precise powder technologies, faster wire technologies providing non-porous products are of great interest. This paper contains a comparative analysis of the effect of two wire technologies – electron-beam additive manufacturing and cold metal transfer – on the structure and mechanical properties of Aluminum Alloy 5056. Electron beam power is close to arc power at optimal printing parameters, but cold metal transfer is cheaper due to the impulse nature of the arc. In addition, the arc method is implemented in an argon atmosphere, and this accelerates the applied layer cooling. In general, the grain structure of the material is refined due to the lower heat transfer and accelerated cooling. This results in increased strength and microhardness. The constant heat removal from the substrate and the increase in the product weight change thermal conditions of the following layer. This is controlled by beam/arc powder reduction, but each layer has its own thermal history affecting the structure and properties. In particular, the more heat is transferred to the layer from the previous layers, the less strong it is. When a certain height (about 30 mm) is passed, cooling is intensified by the large mass of the product and the strength is increased again. This is most characteristic for cold metal transfer. However, these fluctuations are rather small. Mechanical properties along the growth direction are highly stable in both technologies. Cold metal transfer also shows less alloying magnesium burn-off. In general, currently the cold metal transfer technology is more cost effective and provides better quality products.