Russian Journal of Non-Ferrous Metals最新文献

A solid waste from zinc production, zinc plant residue (ZPR) is a valuable resource for the recovery of zinc (Zn), lead (Pb), and silver (Ag). However, the ferritic structure of ZPR makes it difficult to leach these metals. Here, in order to increase the reactivity of the ZPR, mechanical activation using a high-energy ball mill was used. The sample mechanically activated for 15 min was subjected to two-stage leaching with the hydrochloric acid (HCl) solution. At the 1st stage, 74% of Zn was recovered from mechanically activated ZPR sample into the solution under the following conditions: 1 M HCl, 120 min leaching duration, liquid-to-solid ratio (L : S) of 4, the temperature of 25°C, and a rotation speed of 600 rpm. At the 2nd stage, 56% of Pb and 53% of Ag were recovered from the leaching residue, under the following optimized conditions: 8 M HCl, 120 min leaching duration, liquid-to-solid ratio (L : S) of 20, the temperature of 25°C, and a rotation speed of 600 rpm. Сonceptual flow-diagram of the zinc, lead and silver selective recovery from ZPR is proposed herein.

This paper presents the results of theoretical calculations of the reactivity of gold, molybdenite, stibnite, galena, chalcopyrite, arsenopyrite, and pyrite in comparison with experimental data on the floatability of monomineral fractions with butyl xanthate, measured contact angles, and variation in the kinetics of the potential of mineral electrodes. The calculation method establishes the following series of the reactivity and oxidation ability: Au < Sb₂S₃ < MoS₂ < PbS < CuFeS₂ < FeAsS < FeS₂. During flotation in the Hallimond tube, natural gold grains demonstrate the highest recovery (70%) in the range of pH 5–7 as compared to all the sulfides; molybdenite and stibnite are recovered under the same conditions at the level of 50%. With an increase in pH in an alkaline environment to pH 12, the floatability of all the sulfides decreases with the exception of chalcopyrite. It is found that the duration of conditioning with the collector required for the highest recovery is inverse to the reactivity value. The measured contact angle of a drop of water on an untreated surface is the highest for a gold plate (78°) and the lowest for pyrite (67°), but the greatest increase in the contact angle (by 15°) for pyrite is noted after treatment with butyl xanthate at a concentration of 10^–4 mol/L and pH 6; for molybdenite, treatment with butyl xanthate has almost no effect on the measured value of the contact angle. According to the value of the electrode potential in the region of pH 2.0–5.6, the following series is determined: Sb₂S₃ < PbS < CuFeS₂ < FeAsS < FeS₂. Theoretical calculations and experimental data of the study of monofractions of sulfides and gold establish that the conditions of the experiment (pH, duration of conditioning, concentration of the collector) significantly affect the floatability. The calculated data on the reactivity of chemical sulfide compounds and gold in comparison with experimental results show the importance of maintaining certain flotation conditions to create contrast in the floatability of minerals.

At the present time, aluminum alloys with silicon are the most widespread construction materials. In order to increase the mechanical properties of aluminum alloys, modifying with Sr, Ti, and B is used. However, in the foundries, when using scrap and secondary aluminum alloys, the modifying elements are accumulated in alloys in the form of intermetallic particles, which can lead to a decrease in the level of castability. This is connected with the fact that the used modifiers exert a short-term effect and cannot be activated upon remelting. Hence it is necessary to add the modifiers without taking into account the intermetallic particles already contained in the melt. This paper is devoted to studies on the effect of additions of Sr, Ti, and B on the fluidity of an A356.2 grade aluminum alloy determined by means of vacuum fluidity testing. It is shown that, when AlSr10 and AlTi5B1 commercial master alloys are used (containing up to 0.3 wt % Sr and 0.5 wt % Ti), no decrease in fluidity is observed. However, adding the same amount of Ti with the use of a homemade AlTi4 master alloy leads to a considerable decrease in the fluidity. With the help of scanning electron microscopy (SEM) and energy-dispersive X-ray spectroscopy (EDS), the microstructure and phase composition of master alloys and of an A356.2 grade alloy after adding the mentioned master alloys have been investigated. Additionally, the Thermo-Calc software package has been used to evaluate the effect of modifier addition exerted on the phase composition and phase transition temperature of the alloy. It has been established that the effect of the modifier addition on the fluidity of the A356.2 grade alloy is connected with the shape and size of crystals containing the modifying elements in the master alloy structure. When there are coarse crystals formed by such phases, it is quite possible that the crystals are dissolved incompletely, which could hinder the free flow of melt.

In this study, the effects of different treatments (annealing, solid solution and Solution + aging) on the bending and thermal conductivity of SiC_p/Al composites fabricated by the pressure infiltration method were investigated. The fracture form of the composites was indicated to be characteristic brittle fracture with local ductile fracture. The bending strength of the composites was 674 MPa with Solution + aging, which is 57% higher than that in the as-cast condition. The microhardnesses of the composites increased after heat treatment, resulting in the maximum microhardness 276 HV with Solution + aging. By calculating the thermal conductivity of the composites, the order was determined to be cast < annealed < solid solution < solution + aging, and the thermal conductivity with solution + aging treatment reached 182 m^–1 K^–1, which is higher than 153 m^–1 K^–1 in the as-cast condition.

Red mud is another worldwide problem after the bulk solid waste of steel slag.The reaction time between phases of aluminate cement clinker in the molten state is approximately 20 min, and the phase composition obtained is CA. After quenching, a large area of the glass phase appeared in the SEM images of the aluminate cement clinker. The compressive strength and flexural strength at 28 days reached 77.7 and 7.6 MPa, respectively, and the hydration strengths at 1, 3, and 28 days were higher than the strength standard of CA50II aluminate cement.Reconstruction of iron extraction tailings from red mud melting reduction is an effective technology to solve the problems of low cementitious activity, complex composition and large chemical fluctuation of red mud, and it has become an effective technology to improve the comprehensive utilization rate of red mud and promote energy savings and emission reduction.

The efficiency of using rare earth metals largely depends on their impurity composition, which affects the structure and properties of materials. Before the analytical control of materials based on rare earth elements (REEs) and the starting materials for their production, the task is to determine both macrocomponents with high accuracy and impurities with high sensitivity, correctness, and precision. To determine the impurities in REE-based materials in the range from 10^–5 to 5.0 wt %, a complex of methods of atomic emission and mass spectral analysis is frequently used. However, the analysis of REE-based materials, even using these modern highly sensitive methods, is a difficult task due to spectral and matrix interferences. Therefore, different separation/preconcentration procedures are needed to determine both rare earth and non-rare-earth impurities. This article reviews publications of preconcentration methods for spectral and mass spectral methods of analysis of materials based on REEs and some other analytical methods. It is shown that the most common approaches are liquid extraction and chromatography. Sorption, cloud-point extraction, and precipitation are also used. There is no universal approach. Each method discussed in this article has its advantages and limitations. The analytical completion of the method confirms the effectiveness of the selected separation/preconcentration method in each specific case.

The effect of the cold rolling reduction ratio (ε_h) on the microstructure and the complex of mechanical and technological properties of cold-rolled sheets from aluminum alloy V-1579 of the Al–Mg–Sc system has been studied. The influence of the final annealing temperature of sheets rolled with different reduction ratios has been examined as well. The character of plastic anisotropy has been found to change slightly with an increase in ε_h during cold rolling; an increase in tensile strength and yield strength with a decrease in relative elongation is observed. In this case, the anisotropy of the ultimate strength and yield strength is nearly absent. With an increase in the reduction ratio to 30–40%, the anisotropy of the relative elongation increases: the relative elongation in the rolling direction decreases more rapidly. However, after rolling with ε_h > 50%, the elongation anisotropy almost disappears. Regardless of the annealing temperature, samples rolled with a higher reduction ratio have higher strength characteristics. With an increase in the annealing temperature, the ultimate strength and yield strength decrease, while the relative elongation increases. In this case, softening with the annealing temperature occurs more intensely for samples rolled with a lower reduction. For all analyzed regimes, the character of the distribution of anisotropy indices in the sheet plane does not decrease after annealing and corresponds to the deformation type of textures. Moreover, the in-plane anisotropy coefficient decreases after annealing in comparison with a cold-rolled sample. At the same time, the technological properties of samples rolled with a higher degree of deformation are higher after annealing than those of samples rolled with a lower reduction regardless of the annealing temperature.

This paper examines the effects of structural-textural characteristics of sulfide minerals on their leaching from polymetallic concentrates with sulfuric acid and hydrogen peroxide solutions. The polymetallic concentrate was obtained by flotation of polymetallic ore from the Rudnik deposit in Serbia. X-ray diffraction (XRD), qualitative and quantitative mineralogical, scanning electron microscopy (SEM/EDX), and chemical analyses were used to characterize the polymetallic concentrate and leach residue. The polymetallic concentrate contained chalcopyrite, galena, sphalerite, pyrrhotite, and quartz. The total content of sulfide minerals was 69.5%, and the occurrence of free sulfide mineral grains was about 60.9%. The comprehensive thermodynamic analysis was done by HSC Chemistry^® package 9.9.2.3 to determine optimal experimental leaching conditions. Chalcopyrite, sphalerite, and pyrrhotite oxidized during leaching, and dissolution occurred. The oxidized galena remains in the solid residual as insoluble anglesite. Also, elemental sulfur and unleached minerals of copper, zinc, and iron were found in the leach residues. It was found that the structural assembly of sulfide minerals in the leach residue is very favorable and that undissolved sulfide grains are primarily present in free form. Accordingly, there was no reason to reduce the leaching rate with time. The presence of elemental sulfur and anglesite formed in the leaching process and precipitated on the surface of mineral grains was confirmed by XRD, quantitative and qualitative mineralogical analysis, and SEM/EDX.

The results of the studies on the use of collector reagents in the form of a reverse microemulsion (RME) of the water-in-oil type (i.e., water droplets are suspended in the oil phase) for the flotation extraction of lead and zinc minerals are presented. Lead and zinc concentrates and a lead–zinc ore are used as the initial samples for flotation. The concentration of galena in the lead concentrate is 74.7%, and the concentration of sphalerite in the zinc concentrate is 78.7%. Basic collector reagents in the composition of the RME are potassium butyl xanthate (PBX) and kerosene. A nonionic surfactant (NSA) is used to stabilize the RME. Casein is used as additives to the main reagents to eliminate the negative effect of osmotic pressure upon preparing the RME. The transformation of casein to the active soluble form is carried out using sodium sulfide. The particle size in the reverse microemulsion is 12.38 nm. The following options for supplying reagents to the flotation pulp are studied in flotation tests: RME, RME + foaming agent, and potassium butyl xanthate + foaming agent. A T-92 reagent is used as the foaming agent. The consumption of PBX in the composition of the RME and in the classical supply is 26 g/t. The results of laboratory tests show that the method of supplying flotation reagents in the form of an RME leads to an increase both in the flotation rate of lead and zinc sulfides and in their recovery into a foam product. Tests with the use of an RME in the collective flotation cycle of a lead–zinc ore show an increase in the extraction of lead into the total concentrate by 10.8% and zinc by 38.5% in comparison with the classical supply of reagents (collector + foaming agent) in addition to an increase in the flotation rate. An increased selectivity of the action of an RME in relation to zinc sulfides in comparison with lead sulfides is noted. The flotation rate coefficient of sphalerite is 7.8-fold higher when compared to galena. The gain in the extraction into the total zinc concentrate is also higher and is 16.78%, while the gain into the lead concentrate is 1.9% under the same conditions.