Industrial practice has shown that, compared with activated carbon, ion-exchange resins offer advantages in gold recovery from cyanide solutions and pulps, reducing both capital and operating costs. New resin types selective for the dicyanoaurate include the weak-base AuRIX100 resin containing active guanidine groups, the weak-base Lewatit MP–64 and IRA–94S with tertiary amine functional groups, the strong-base macroporous Minix resin with active tributylamine groups, and the bifunctional resins Ionac A–641 and Reillex HPQ, which contain up to 70 % quaternary ammonium and pyridinium groups and approximately 30 % tertiary ammonium groups. An important advance in activated-carbon sorption technology is the introduction of the Pumpcell system, which uses a carousel arrangement of sorption columns and stationary activated-carbon beds confined by drainage screens. The main advantage of this system is that gold loading of activated carbon is twice as high as that achieved in the standard CIP process. Higher sorption kinetics and the absence of pulp backmixing reduce capital costs by decreasing the amount of loaded sorbent and the size of sorption, desorption, and regeneration equipment. Another important equipment-related advance is the use of pulsed Gekko columns.

The removal of lead impurity from nickel chloride solutions by sorption on the weak-base anion exchange resins Lewatit A365, Purolite S984, Purolite S985, Puromet MTS9841, and Purolite A110 was studied.  All anion exchangers showed selective sorption of lead present as chloride complexes, although their selectivity differed. In terms of lead selectivity in the presence of a large excess of nickel chloride, the anion exchange resins were arranged in the following order: Lewatit A365 ˃ Puromet MTS9841 ˃ Purolite S984 ˃ Purolite S985 ≥ Purolite A110. An increase in nickel concentration in solution  adversely affected the lead capacity of Lewatit A365 and MTS9841. The presence of sodium sulfate in solution, up to a sulfate ion concentration of 30 g/L, had no adverse effect on lead sorption. The best lead removal was achieved by sorption from solutions containing 100–120 g/L nickel at pH not higher than 3.0–3.5. When a model solution corresponding in composition to a typical chloride-sulfate nickel electrolyte containing119 g/L nickel, 30 g/L sulfate ion as sodium sulfate, and 1.12 g/L lead was passed through columns packed with Lewatit A365 or Puromet MTS9841, more than 1000-fold purification from lead impurity was achieved for the first 15 or 36 column volumes of solution passed through Puromet MTS9841 or Lewatit A365, respectively. Most of the lead sorbed by the anion exchangers, 93–99 %, was desorbed with distilled water at 50 °C, while the residual lead was completely desorbed with a 1 M NaOH solution.

The kinetics of aqueous lithium leaching from black mass of spent lithium-ion batteries was studied. The experiments were carried out at 25 and 80 °C, a liquid-to-solid ratio (L:S) of 10, and constant stirring for 2 h. It was found that the most lithium extraction, approximately 55 %, occurs within the first 20–30 min, after which the process rate decreased sharply. The pseudo-first-order, pseudo-second-order, Elovich, Avrami, and shrinking core models were used to describe the leaching kinetics. The classical shrinking core model was shown to be inapplicable (R² ≤ 0.79). Although the Avrami model provided a satisfactory visual fit, it yields a negative apparent activation energy, indicating that it was unsuitable for describing the process. The Elovich model showed the best agreement with the experimental data and, in nonlinear regression analysis, had the lowest AICc and BIC values. The activation energy calculated from the temperature dependence of the α parameter was 31.8 kJ/mol, corresponding to mixed process control. Despite their high coefficients of determination in linear analysis, the pseudo-first-order and pseudo-second-order models gave substantially poorer results in nonlinear estimation.

The development of the Russian aluminum industry is proceeding in several areas, among which deep modernization of aluminum production plays a key role. One of its major components is the conversion of Soderberg cells to prebaked anode cells. For this modernization, it is important to understand the state of magnetohydrodynamics of the cryolite-alumina melt as it has a significant effect on cell operation. Mathematical modeling was used to assess the feasibility of converting cells with self-baking anodes to prebaked anode cells without upgrading the busbar system, i.e., with minimal capital expenditure. The already upgraded busbar system for the S-8BM(E) Soderberg cell was used as the basis. The specialized MHD-Valdis and Blums V5.07 software packages were used to calculate the MHD operating parameters of the cell without changing the design of the cathode busbar system, anode risers, or cathode assembly. The calculation procedure involved sequentially solving the electrical problem to determine current distribution, temperature, and current densities in the sections of the cell electrical circuit. The magnetic problem was then solved to determine the magnetic field characteristics in the electrolyte melt and cathode metal, taking into account the effect of ferromagnetic masses. The Lorentz forces and their resulting effect on the static tilt of the cathode metal were then calculated, together with the metal circulation velocities, to determine the final MHD stability margin of the cell. The results show that the conversion of Soderberg cells to prebaked anode cells improves the main MHD operating parameters of the cell: the mean and mean absolute values, as well as the absolute minimum and absolute maximum values, ​​of the vertical component of magnetic flux density decrease. In addition, the maximum cathode metal velocities decrease by 31.37 %, and the total static tilt of the cathode metal decreases by 21.25 %.

This study investigates the electrochromic properties of TiO₂ oxide films produced by the electrochemical oxidation of titanium in alkali metal nitrate melts with additives. The study focuses on the contrast ratio (K), a key parameter for evaluating the performance of electrochromic materials. It was found that the highest contrast ratio values of K = 7÷8 were achieved during anodic oxidation in melts containing potassium fluoride (KF) at a concentration of 0.01–0.04 mol/kg under the following conditions: temperature of 625 ± 10 K, voltage of 20 ± 5 V, and process duration of 5÷12 min in potentiostatic mode. The introduction of fluoride ions promotes the formation of a defect-rich oxide layer, thereby improving its electrochromic characteristics. The optimal synthesis conditions yield TiO₂ films with high corrosion resistance and reversible electrochromic behavior. Visual observations and quantitative measurements confirmed that these films exhibit intense dark-blue coloration under cathodic polarization and complete bleaching under anodic polarization. Long-term cycling tests in 1 M H₂SO₄ solution, equivalent to 2 N, demonstrated high stability of the electrochromic properties of the oxide layers, making them promising for use in indicator devices, such as displays and smart-window applications. The results also emphasize the importance of electrolyte composition and oxidation parameters for obtaining reproducible, high-quality electrochromic materials. The obtained data can be used for further optimization of synthesis processes and the development of TiO₂-based composite materials.

Thermodynamic calculations were used to determine the enthalpy, entropy, and Gibbs energy of formation of neodymium compounds: lanthanite Nd (Nd₂(CO₃)₃·8H₂O), tengerite (Nd₂(CO₃)₃·3H₂O), hydroxylbastnasite, and kozoite (NdHCO₃). The formation of neodymium carbonate precipitates with a tengerite-type structure without heating was studied during reverse precipitation, i.e., by feeding a neodymium nitric acid solution (~1 mol/L Nd) into a 20 % of ammonium carbonate salt solution with pH ≥ 9.0. This was confirmed by morphological and X-ray diffraction studies of the corresponding samples. The possibility of improving carbonate precipitation and subsequent pulp filtration was demonstrated by simplifying by preparation of neodymium carbonate powders with a tengerite-type structure and particles and agglomerates uniform in shape and size. The increase in process productivity was attributed to the use of feed solutions with higher neodymium concentrations and the elimination of stage in which the precipitate is held under the mother liquor for recrystallization. The use of a 20 % ammonium bicarbonate solution did not lead to the formation of precipitates with an ordered structure, because the pH of the initial reagent solution did not exceed 8.76 and therefore lay outside the region of neodymium carbonate formation with a tengerite-type structure, as established by thermodynamic analysis. The results indicated that further research aimed at optimizing neodymium carbonate precipitation from nitric acid solutions is promising for obtaining precipitates with the required characteristics for the development of functional materials.

The high-entropy CoCrFeMnNi Cantor alloy is promising for energy applications and space exploration due to its high corrosion resistance and excellent low-temperature ductility. Surface ion-plasma saturation of this alloy with nitrogen and carbon may further improve its service properties; however, this issue has not yet been studied in detail. In this work, uniaxial static tensile tests and impact toughness tests were used to study the effect of ion-plasma nitriding and nitrocarburizing at 400 and 500 °C for 1 h on the deformation behavior, mechanical properties, and impact toughness of the high-entropy Cantor alloy over a wide temperature range. It is found that the formation of a hardened surface layer consisting of heterophase composite and diffusion sublayers increased the yield strength of the alloy specimens by up to 25 % and was accompanied by a slight increase in tensile strength, up to 5 %, in the temperature range from –196 to +300 ℃. In the same temperature range, the elongation to fracture of specimens with hardened surface layers remains high (δ_U > 65 %). The development of dynamic strain aging in the Cantor alloy at a test temperature of 300 °C was experimentally confirmed, as indicated by serrated tensile curves. Surface ion-plasma nitriding was found to partially suppresses this effect, whereas it was completely absent in nitrocarburizing specimens. Ion-plasma treatment under the selected conditions has virtually no effect on the impact toughness of Cantor alloy specimens at temperatures from –196 to +23 °C. This confirms the beneficial effect of the treatment on the strength charac­teristics of the material without loss of its main advantages, namely high ductility and impact toughness.