Arailym Mukangaliyeva

Nitric–sulfuric acid leaching of substandard molybdenite concentrate from the Aktogay deposit (Kazakhstan) transfers only part of the molybdenum into solution: under the baseline process conditions, approximately 30% of the sulfide is oxidized, while roughly 70% of the molybdenum remains in the leach cake as unoxidized molybdenite. Molybdenum is thus distributed between two technologically dissimilar streams—the solution and the solid cake—and complete recovery requires processing of both. In the present work, both branches are combined into a single integrated scheme applied to a common feedstock. In the first (sorption) branch, molybdenum is concentrated from the solution. Among four anionites tested (Purolite A-100, Amberlite IRA-95, AV-17-8, and Lewatit M-800), Amberlite IRA-95 exhibited the best performance (sorption 84.21%, desorption with ammonia solution 82.15%, and selectivity coefficients Mo/Cu = 304.7 and Mo/Fe = 192.2). To remove iron, copper, and silicon impurities prior to concentration, a two-stage scheme is proposed incorporating preliminary impurity sorption on KU2-8 cationite (separation coefficients Mo/Cu = 5.7, Mo/Fe = 3.58, Mo/SiO₂ = 2.17). In the second (roasting) branch, the cake is processed: the cake, granulated with molasses, is subjected to oxidative roasting at 600 °C for 150 min under an oxygen flow (2 dm³/min) until complete desulfurization is achieved, after which the calcine is leached with ammonia. Both streams converge into a single product: the ammoniacal desorbate from the sorption branch and the alkaline solution from the calcine are acidified with nitric acid to pH 2–3, ammonium paramolybdate is precipitated by evaporation, and the precipitate is calcined to molybdenum trioxide. The resulting MoO₃, according to XRD data, is represented predominantly by orthorhombic α-MoO₃ (molybdite). Overall, the proposed two-branch scheme closes the molybdenum material balance for the substandard concentrate from both sides and outlines a technically straightforward pathway for bringing stockpiled technogenic raw material into processing.

TiN/CrN multilayer coatings with bilayer periods of 20 and 30 nm and TiN:CrN layer thickness ratios of 1:1, 1:2 and 2:1 were deposited on 40Kh steel substrates by pulsed direct current magnetron sputtering (pDCMS). The phase composition (XRD), microstructure (SEM), mechanical (nanoindentation, scratch testing), tribological (dry sliding and boundary lubrication), and corrosion (potentiodynamic polarization in 3.5 wt.% NaCl) characteristics of the coatings were examined. Increasing the TiN volume fraction increased nanohardness and elastic modulus reaching a maximum H³/E² = 0.186 GPa. The Λ30-TiN(20)/CrN(10) coating showed the best adhesion (L_c1 = 14.4 N, L_c2 = 17.7 N, CPR_S = 48 N²) and the lowest wear rate both under dry sliding and under boundary lubrication (1.2 × 10⁻⁵ mm³/(N·m)). In contrast, CrN dominance (Λ30-TiN(10)/CrN(20)) sharply degraded the tribological behaviour (the wear rate increased by almost an order of magnitude) and caused catastrophic localized pitting in the corrosion tests. At the same time, the best corrosion resistance (E_corr ≈ −0.47 V, the most extended quasi-passive region) was achieved at the smallest bilayer period. A balanced composition, Λ20-TiN(10)/CrN(10), owing to the highest density of interlayer boundaries, effectively blocks through-thickness growth defects. The architectures that are optimal in terms of mechanical/tribological and of corrosion criteria do not coincide, which indicates that the TiN:CrN ratio has to be chosen according to the dominant type of service loading. The results obtained show that varying the thickness ratio of the TiN and CrN layers at bilayer periods of 20 and 30 nm makes it possible to tune the balance of hardness, wear resistance, adhesion and corrosion resistance of multilayer coatings on structural steels.

Spent titanium chlorinator melt is a potential technogenic source of scandium, but its recovery is complicated by high contents of iron, aluminium and alkali and alkaline-earth chlorides. This study assessed a sequence of hydrochloric acid leaching, Fe(III) reduction with ascorbic acid, sorption on the strong-acid cation exchanger Lewatit MonoPlus SP112H, desorption with acidified ammonium sulfate solution, oxalate precipitation, calcination and an additional column purification. In a scaled-up test, leaching of 4 kg of the spent melt with 5% HCl produced 25.5 L of filtrate containing 475.30 mg Sc. Two-stage sorption recovered 90.9% of the scandium, and the overall desorption degree reached 94.8%. The kinetic data were better described by the non-linear pseudo-second-order model (R² = 0.890–0.938). Precipitation and calcination gave 0.60 g of an intermediate oxide product with 65.0 wt% Sc, and the additional purification 0.45 g of a final oxide product in which X-ray diffraction identified cubic Sc₂O₃ as the predominant crystalline phase; the elemental analysis gave a purity close to 98 wt%. Recovery into the final oxide reached 61.92% of the scandium in the filtrate. Iron co-sorption and scandium losses during the additional purification remained the principal limitations of the process.

In this study, the partial pressure values of magnesium over Mg–Ag system alloys were determined by the boiling point method and are presented as a temperature–concentration dependence. A similar dependence for the partial vapor pressure of silver was obtained with the numerical integration of the Gibbs–Duhem equation. The boundaries of the vapor–liquid equilibrium fields were calculated at atmospheric pressure (101.3 kPa) and under vacuum (1.33 kPa). A complete phase diagram was constructed, including the boundaries of the liquid–vapor phase transition at the specified pressures. It was shown that the composition of the equilibrium vapor phase is represented almost entirely by magnesium over nearly the entire range of component concentrations. Thus, when the melt contains 1 wt. % in the melt and exhibits a boiling temperature of 1187 °C (1460 K), the vapor phase contains 94.67 wt. % magnesium, with silver accounting for the remainder. Therefore, the separation of liquid magnesium–silver alloys presents no significant technological difficulties. Based on the thermodynamic activities of the components, the partial and integral mixing functions, namely, entropy and enthalpy, were determined. The thermodynamic functions of formation and evaporation of Mg–Ag system alloys may be used for energy calculations of distillation processes and will supplement the physicochemical database.

The development of multilayer coatings based on titanium carbides and nitrides remains one of the most active areas in materials science, owing to their ability to markedly enhance wear resistance and extend the service life of machine components. Particular interest is currently focused on tailoring conventional TiN/TiCN architectures through alloying metal additions. In this study, the tribological and mechanical performance of aluminum- and zirconium-doped TiN/TiCN multilayer coatings deposited by direct-current magnetron sputtering onto 41Cr4 steel was investigated. The morphology, elemental distribution, and phase constitution of the multilayer coatings were examined. It is shown that increasing the number of bilayers from two to four in TiN/TiCN–based multilayer coatings leads to improved tribomechanical characteristics. It was determined that zirconium provides a more pronounced beneficial effect than aluminum. The four-bilayer TiZrN/TiZrCN coating simultaneously exhibited the lowest coefficient of friction (0.11) and wear rate (10⁻⁶ mm³ m⁻¹ N⁻¹) at a hardness of 16.4 GPa.

Depletion of reserves of rich copper–porphyry ore deposits necessitates the development of highly efficient methods for Mo (VI) extraction from complex, corrosive hydro-metallurgical media. The present study undertakes a comprehensive assessment of sorptive concentration of Mo (VI) from strongly acidic sulfate solutions (120 g/L H₂SO₄) by employing a spectrum of commercially available strong- and weak-base anion-exchange resins. It has been established that the macroporous weak-base anion exchanger Purolite A-100 demonstrates decisive superiority over gel-type analogs (Lewatit M-800, AB-17), facilitating unimpeded intra-gel diffusion of bulky molybdenyl sulfato-complexes anions, thereby circumventing the obstructive “sieve effect.” Thermodynamic and kinetic investigations revealed that the sorption process exhibits pronounced concentration- and pH-dependent characteristics. Peak extraction efficiency (up to 95.91%) is achieved at pH ≈ 1, a finding that correlates with the region of maximal protonation of tertiary amino groups within the resin matrix. Kinetic acceleration of mass transfer upon heating to 80 °C has been experimentally confirmed, yielding 94.6% extraction within 60 min. The obtained results corroborate the prospective integration of macroporous weak-base anion exchangers into operational hydro-metallurgical schemes as an environmentally benign and efficacious alternative to conventional solvent extraction of molybdenum.

Recovery of scandium from chloride-bearing process liquors formed during titanium–magnesium production remains constrained by trace-level metal content and chemically aggressive solution matrices. Within the present study, the retention behaviour of Sc³⁺ species in strongly acidic chloride media was examined through batch-mode interaction with gel-type sulfonated cation exchangers, namely KU-2-8, Lewatit SP112H, Purosorb SAC140H, and Purolite C-150H. Quantitative evaluation of sorption efficiency was performed by calculating equilibrium uptake (q_e), phase distribution factor (K_d), and percentage recovery (R). Under identical liquid–solid ratios, the Lewatit SP112H matrix exhibited superior affinity toward dissolved scandium, achieving q_e = 179.82 mg/g and K_d = 172.41 mL/g. Equilibrium fitting procedures revealed that scandium uptake by Purosorb SAC140H conforms to monolayer-type retention described by the Langmuir formalism (R² = 0.9786), whereas sorption on Lewatit SP112H proceeds over energetically non-uniform sites and is more adequately represented by Freundlich and Dubinin–Radushkevich approximations. The observed retention characteristics establish a selection framework for ion-exchange media applicable to scandium concentration from acidic chloride hydrometallurgical streams.

The growing global demand for lithium, driven by its pivotal role in battery production, highlights the need for alternative technologies to recover this metal from low-grade and anthropogenic raw materials. This study investigates lithium extraction from aluminosilicate tailings of rare-metal production by sulfate roasting with concentrated sulfuric acid, followed by aqueous and hydrochloric acid leaching. Mineralogical analysis confirmed lithium mainly in muscovite and biotite (isomorphic substitutions) and partly as spodumene within the aluminosilicate matrix. The optimal parameters of thermochemical treatment were determined as 300 °C for 1 h at a liquid-to-solid ratio of 1:6. Subsequent aqueous leaching (90 °C, 1 h, L/S = 6:1) achieved a lithium recovery of 82.3%, while HCl proved less effective. Using response surface methodology (RSM) and a central composite design (CCD), a regression model was developed predicting up to 93.4% lithium extraction at 90 °C, a liquid-to-solid ratio of 10:1, and a leaching duration of 75 min. The calculated values showed good agreement with experimental data obtained at 90 °C, L/S = 10:1, and 30 min leaching, yielding 91.92% lithium recovery. These results confirm the efficiency of the proposed thermochemical approach and provide a scientific foundation for its further development and industrial scale-up.

This study explores the intensification of molybdenite concentrate processing through a synergistic hydrometallurgical approach using sulfuric acid, nitric acid, and their combination to enhance leaching efficiency while minimizing environmental impact. Molybdenum, a strategic metal widely used in advanced engineering and catalytic systems, presents extraction challenges due to the refractory nature of molybdenite (MoS₂). The experimental approach incorporated oxygen sparging and mechanoactivation to improve dissolution kinetics and molybdenum availability. A central composite design (CCD) of response surface methodology (RSM) was employed to develop a predictive model for optimizing the leaching parameters. Acid concentration, temperature, and leaching time were systematically varied, allowing for the identification of statistically significant factor interactions and optimal operating conditions. The model demonstrated strong predictive capability with high adjusted and predicted R² values, validating its suitability for process optimization. Optimal leaching conditions were identified as 50 g/dm³ HNO₃ + 200 g/dm³ H₂SO₄, a temperature of 95 °C, a leaching time of 240 min, and a solid-to-liquid ratio of 1:6, resulting in a maximum molybdenum extraction efficiency of 72.6%. This performance was attributed to enhanced oxidative decomposition and stable complexation of molybdenum species. This study provides a scalable and environmentally conscious framework for molybdenum extraction, with implications for sustainable metallurgy and industrial applications.