The process of separation in a ferrofluid is recommended for gold separation from placer beneficiation products. The process of magnetic fluid separation is based on the ponderomotive force of the inhomogeneous magnetic field appeared in ferrofluids in addition to the pushing gravity force. The horizontal component of this force in a separation medium participates in the movement of bodies along an equipotential surface across the working area – to the separation cell walls and towards the central plane of the pole gap, and the longitudinal component participates in the movement along the working area. In order to improve the technological parameters of the process, it is recommended to limit the transverse displacements of the bodies by vertical partitions installed in the separation medium along the separator pole gap. The theoretical study results regarding particle motion in the separator working area suggest that the wall effect is manifested in the appearance of a flow opposite to the direction of particle motion. This increases the hydrodynamic drag force and reduces the speed of particle movement. It is shown that the decrease in the time of light concentrate fraction presence in the separator working area with vertical walls promotes an increase in the productivity of the process with respect to the initial feed and heavy fraction productivity (gold extraction into the heavy fraction). The mathematical methods of experimental design were used to perform investigation tests of competing methods of separation on artificial mineral mixtures and heavy gold-bearing concentrates isolated from placer sands. It has been proved that the transition from ferrofluid volume separation to separation using the developed method increases the unit productivity by 9 %, and the gold extraction into the heavy fraction from 84,34 to 91,77 % due to light fraction losses reduced from 15,46 to 7,96 %. Heavy fraction yield lowered by 11,6 rel.% made it possible to obtain a material containing over 800 kg per ton of gold.

The article presents the results of material composition studies of a refractory gold-copper-arsenic concentrate. The nature of gold dissemination in the mineral components of the studied flotation concentrate shows that gold is more associated with sulfides and less with iron hydroxides. The results obtained indicate that gold is predominantly small. The process flow scheme is offered for processing of the studied flotation concentrate. It includes the following operations: ultrafine grinding, autoclave oxidation, alkaline atmospheric treatment of autoclave oxidation cake with subsequent sorption cyanidation. The effect of feed size on the behavior of components in autoclave oxidation was studied. This process was investigated using a sulfuric acid solution with a concentration of 50 g/l at the L : S = 2 : 1 ratio, oxygen pressure of 0,8–1,0 MPa, and temperature of 95±10 °C. It was found that the optimal duration of autoclave oxidation is 4 h. High performance was reached when the flotation concentrate was subjected to preliminary ultrafine grinding to –0,020 mm (85 %) Alkaline atmospheric treatment of the solid cake was carried out under the following conditions: L : S = 3 : 1 ratio, CaO feed – 100 g/kg, temperature – 95 °C, duration – 2 h. Fixed residue of autoclave oxidation was subjected to CIL for 8 h at the ratio of L : S = 3 : 1, pH = 9,5÷11,0, NaCN concentration – 1 g/l, coal feed – 5 vol.%. It was found that this technology provides up to 96 % gold recovery.

A thermodynamic analysis of phase equilibria in a Cu–Al–Cr–O system was performed. The study involved thermodynamic modeling of the liquidus surface of the Cu2O–Al2O3–Cr2O3 oxide phase diagram. To describe the thermodynamic activity of the molten oxide, an approximation of the sub-regular ionic solutions theory was used with the energy parameters determined in the modeling process. Melting characteristics of CuCrO2 were also evaluated during calculations. Calculation results were used to determine the coordinates of invariant equilibria points in the Cu2O–Al2O3–Cr2O3 ternary oxide system. The study also involved thermodynamic modeling of interactions in the Cu–Al–Cr–O system in the conditions of a copper-based metal melt. The temperature function of the reaction equilibrium constant was determined for the formation of solid CuCrO2 from the components of the Cu–Al–Cr–O molten metal system. The temperature function was obtained for the first order (Wagner’s) interaction parameter of Cr and O dissolved in liquid copper. The results of thermodynamic modeling for the Cu–Al–Cr–O system are represented as the surface of components solubility in metal, which allows us to relate the quantitative changes in the molten metal concentration to the qualitative changes in the composition of resulting reaction products. As a result of modeling, it was found that the given considerable concentrations of Al and Cr in the Cu–Al–Cr–O molten copper system form the |Al2O3, Cr2O3|ss solid solution particles as primary reaction products. The results of the study may be used to improve the chromium bronze smelting process.

The paper studies the scientific basis of the pyrometallurgical treatment process for electric steelmaking dust containing zinc ferrites. Thermodynamic analysis of zinc ferrite decomposition by lime was performed. According to the calculated data analysis, dust requires adding at least 46 % of CaO to decompose more than 90 % of ZnFe2O4, and at least 60 % of CaO to decompose more than 95 % of ZnFe2O4. The calculation results were verified by the laboratory furnace experiments. Experimental dust calcination in air with lime added up to 60 % of dust mass at a temperature of 1000 °C and a holding time of 4 h confirmed that zinc ferrite is decomposed by calcium oxide with the formation of zinc oxide and dicalcium ferrite. In addition, 50 kg of sublimates per 1 ton of dust were obtained containing 29 % of lead and 15 % of zinc. Dust calcination with the addition of lime can be used to transform zinc from ferrite to a soluble oxide form. Intermediate products resulting from calcination can be used for zinc and lead recovery. After zinc leaching it is possible to obtain the iron-containing product applicable in ferrous metallurgy. The approach has a variety of technological advantages in comparison with the known Waelz process. In particular, calcination with lime requires lower temperature (1000 °C) than the known technology (1250 °C), it eliminates the second stage of Waelz treatment necessary to purify zinc oxide fed for leaching from halides, significantly reduces coke consumption and simplifies gas cleaning from dust due to the 6–8 times lower quantity of sublimates.

The object of the study was oxidized copper ore of the Zhezkazgan deposit and technical sulfur, oil industry waste. The oxidized copper ore – sulfur system was studied to explore the possibility of sulfidation of oxidized copper ores with sulfur. Oxidized copper ore is involved in production in view of depleted sulfide copper minerals. Many studies focuses on the sulfidation of oxidized copper minerals in order to improve the efficiency of copper extraction from this type of feed. It is also important to study the sulfidation of oxidized copper ores with technical sulfur as an oil industry waste. The thermodynamic evaluation of metal oxides sulfidation using hydrogen sulfide, sulfur or other sulfur-containing compounds is of interest in terms of preparing metallurgical raw materials for enrichment. The use of technical sulfur also solves the oil industry problems. Thermal and X-ray diffraction analyzes were used to study the oxidized copper ore – sulfur system. Thermal analysis was performed on the Q-1000/D derivatograph (F. Paulik, J. Paulik and L. Erdey system) manufactured by MOM, Hungary. Due to the peculiar thermal behavior of sulfur (low melting and boiling points) included in the charge composition (low interaction temperature) the heating temperature of a number of samples was limited to 20~650 °C. Heating was performed in a dynamic mode with calcined Al2O3 as a reference substance and a test charge of 100 mg. It was found that sulfur reacts with oxidized copper minerals at the non-isothermal heating of the reaction mixture in the temperature range 160–350 °С, and the sulfidation reaction is accompanied by the release of heat and sulfur dioxide. The results of X-ray diffraction analysis of products after thermal interaction confirm the copper sulfide formation.

The paper studies rhenium (VII) sorption from sulfuric acid solutions by impregnates based on macroporous polymer carriers (copolymers of styrene with divinylbenzene, weak acid cation exchange resion) containing commercial trialkylamine (ТAA). The study provides equilibrium and kinetic characteristics of rhenium recovery by the impregnate based on the macroporous weakly acidic cation exchange resin (K-TAA) having the best rhenium capacity. The maximum coefficient of rhenium distribution in the K-TAA impregnate is observed in sorption from pH = 2 solutions. The rhenium sorption isotherm is described by the Langmuir equation with the K = 29±2 ml/g constant. A limited solution volume method was used to obtain the integral kinetic curves of sorption with a half-reaction time value considered to calculate the effective coefficients of rhenium diffusion in the impregnate amounted to (3,8·10–11 (295 K) and 1,3·10–10 (308 K) m2/s). Kinetic results linearized by the equations of models (pseudo-first, pseudo-second order, Elovich and inner diffusion) showed that kinetic curves with the highest correlation degree are described by the pseudo-second order equation with the 0,00056 (295 K) and 0,00059 (308 K) g·mg–1·min–1 rate constants. The apparent activation energy of rhenium sorption (39±2 kJ/mol) was calculated using the Arrhenius equation. The K-TAA impregnate was tested for rhenium sorption from the eluate obtained by rhenium desorption from the Purolite A170, weak base anion exchange resin pre-saturated with rhenium from the complex pregnant solution for leaching of products derived from poor rhenium-containing copper sulfide raw materials processed.

The paper presents the results obtained when studying how the condition of the casting wheel working surface in the rotary continuous casting machine (CCM) influences the quality of copper metal products on the Southwire modern high-tech continuous casting and rolling line at PJSC «Artemovsk Non-Ferrous Metals Processing Works». Industrial research identified the main defects occurred on the casting wheel working surface during its operation: transverse cracks located on the working surface in planes perpendicular to the casting direction – both at the trapezoid base and on its side faces (10–45 mm long cracks located 7–40 mm apart); dents, longitudinal dimples and scratches along the direction of billet movement mainly in the obtuse angles of the trapezoid and in areas adjacent thereto; deformed wheel profile in the corners of the working channel, primarily due to friction wear. It was found that the main causes of surface and internal cracks in the wheel are challenging temperature modes of operation associated with the technology of copper casting on the rotary CCM. Alternating cycles of heating and cooling of individual sections of the casting wheel cause two-dimensional tensile stresses in its internal layers resulting in cracks. An equally important factor in crack formation is further excessive secondary cooling of the wheel with water as it is followed by reheating of the billet surface. However, a lowered temperature gradient of the wheel surface between the cooling areas will reduce the degree of surface deformation, increase the service life and improve the quality of continuously cast billets and finished steel.

The relevance of this paper is connected with rising accuracy requirements to stamped parts made of aged aluminium alloys applied also for layered composite making. These requirements can be met by controlling the sheet blank structure, and particularly its phase composition. The paper provides experimental results obtained when studying the effect of aging modes on the composition, dispersed phase distribution pattern and formability of sheet samples made of D16 (AA2024) aluminium alloy. Heat treatment consisted in quenching from a temperature of 500 °С into room temperature water and further aging: natural aging during 7 days, artificial aging at temperatures of 50, 100, 150 and 200 °С and holding at each temperature during 15, 30, 60, 120 and 240 minutes. The quantitative method is proposed to evaluate the dispersed phase distribution pattern by microstructure pictures. Formability was evaluated using the stamping number, i.e. a proof/ultimate factor. It was found that the stamping number rises as the aging temperature and holding time are increased, which shows the lower alloy applicability for sheet stamping operations. No dispersed phase was formed when aged at t = 50 °С in both optical metallography and scan electron microscopy cases. The non-uniformity of dispersed phase distribution inside a grain rises at initial aging stages with a holding time less than 1 hour at 100, 150 and 200 °С and decreases with a further increase in the holding time up to 4 hours. No correlation was observed between the uniformity of phase distribution and the stamping number. The chemical composition of phases has a greater effect on the formability and changes depending on a heat treatment mode: annealing and natural aging primarily lead to the θ and S phase precipitation; aging at temperatures below 150 °С with a holding time less than 1 hour lead to the θ, S and T phase precipitation; θ phase appears after aging at temperatures over 150 °C with long holding times.

The microstructure peculiarities of the new Al–Hf–Sc master alloys were studied using the methods of optical and scanning electronic (SEM) microscopy in combination with EDX analysis. The alloys studied included the meta-stable intermetallic compounds (aluminides) having cubic lattices identical to those in the matrix of aluminum alloys. Binary and ternary alloys were melted in graphite crucibles at a carbon-resistance furnace under an argon atmosphere. Al–0,96at.%Hf (5,98 wt.% Hf) and Al–0,59at.%Hf (3,77 wt.% Hf) alloys were prepared by superheating above the melting point up to about 200 and 400 degrees respectively. Melts were poured into a bronze casting form where crystallization rate was ~103 degrees/sec. Besides stable aluminides with tetragonal lattices, Al3Hf metastable aluminides with cubic lattices were formed only in the melt superheated by 400 degrees above the melting point. The degree of superheat for ternary alloys where Aln(Hf1–xScx) meta-stable aluminides were formed was 240, 270 and 370 degrees. The hafnium fraction in the Aln(Hf1–xScx) aluminides changed from 0,46 to 0,71 depending on the Hf : Sc ratio in the alloy. The master alloys produced (at.%): Al–0,26Hf–0,29Sc and Al–0,11Hf–0,25Sc (wt.%: Al–1,70Hf–0,47Sc and Al–0,75Hf–0,42Sc) demonstrate fine grain structures with meta-stable aluminides of Aln(Hf0,58Sc0,42) and Aln(Hf0,46Sc0,54) compositions respectively. Aluminide sizes are less than 12 and 7 μm. Their crystal lattice mismatch with the aluminum alloy matrix lattice is less than for Al3Sc. This fact allows us to expect high modifying effects of the experimental Al–Hf–Sc master alloys in their further application. In addition, replacement of expensive scandium with hafnium in the master alloys can reduce scandium consumption considerably.

The study covers the electrochemical and corrosion behavior of 4 alloys (wt.%): Al–6Ca (Al6Ca), Al–6Ca–1Fe (Al6Ca1Fe), Al–1Fe (Al1Fe), AK12M2. High Fe content (up to 1 %) in the alloys is required for high productivity of die-casting processes. Electrochemical tests were conducted in the 3 % NaCl aqueous solution at 26±0,5 °С using the IPC-Pro 3A (IPC-2000) digital potensiostat. Potentiodynamic anodic polarization was performed at a scan rate of 1 mV/s. The initial polarization potential was –800 mV (SHE). The potential scanning direction was reversed at a «critical» current density icr = 10 mA/cm2 with the same scan rate of polarization. The tendency of the alloy for pitting formation was determined by the Qdir/Qrev ratio (the amounts of electricity passed through the electrode before pits occur and before repassivation) and the bases of pitting resistance: difference between the pitting potential (Epit) and the equilibrium potential (Eeq); difference between the repassivation potential (Erep) and the equilibrium potential (Eeq). Corrosion tests of cast aluminum alloys were carried out by holding the samples in a salt spray chamber and in the 3 % NaCl aqueous solution for 700 h. The Olympus GX51 optical microscope was used to assess the morphology of sample surfaces after their holding. It is found that the Al6Ca1Fe and Al6Ca experimental alloys placed in the 3 % NaCl aqueous solution are not susceptible to pitting corrosion as opposed to the AK12M2 industrial alloy and Al1Fe. It is assumed that the higher corrosion resistance of Al6Ca1Fe is due to the entry of Fe into the Al10CaFe2 intermetallide. The intermetallide is not an effective cathode with respect to Fe due to significant negative potentials of Al and Ca. Al6Ca1Fe is a promising alloy for industrial use due to its high casting and mechanical properties that are not inferior to the eutectic silumin alloy and even surpass it in terms of corrosion resistance.