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Bismuth (III) sulfide has been widely researched in recent years due to its application, but little emphasis has been placed on research regarding its behavior at elevated temperatures. This is of great importance, considering that bismuth, in the form of Bi2S3, is found in copper sulfide concentrates and is considered one of the most harmful components, along with lead, arsenic and antimony. The removal of these substances is one of the basic tasks in the processes of pyrometallurgical extraction of copper, in order to obtain a high purity metal. In order to better understand the behavior of bismuth (III) sulfide during oxidation at elevated temperatures, this paper characterized the synthesized sample of Bi2S3 at room temperature and the oxidation products at 500 °C by X-Ray diffraction (XRD), as well as thermodynamic, thermal and kinetic analysis of the oxidation process of Bi2S3 at elevated temperatures. In order to understand the behavior of Bi2S3 during oxidation and the distribution of oxidation products, phase stability diagrams in the Bi-S-O system were constructed at different temperatures and the values of the Gibbs free energy change at 400 °C and 1000 °C were calculated. Kinetic analysis of Bi2S3 oxidation process was performed by Kissingers method in non-isothermal conditions.

In this paper, the influence of structural and textural characteristics of sulfide minerals on their leaching from a polymetallic concentrate by sulfuric acid and sodium nitrate solution is presented. The starting material was Pb–Zn–Cu sulphide polymetallic concentrate enriched during the flotation of a polymetallic ore in the "Rudnik" flotation plant (Rudnik – Serbia). Leaching experiments were carried out in a closed glass reactor, which provides stable hermetic conditions and allows heating at constant temperature. Chemical, XRD, qualitative and quantitative microscopic and SEM/EDX analyses were used to characterizes samples of the polymetallic concentrate and leach residue. It was determined that chalcopyrite, sphalerite, galena, pyrrhotite and quartz were present in the polymetallic concentrate. The content of sulphide minerals was 69.5%, of which 60.9% occurred as liberated grains: 88.3% of chalcopyrite, 59.3% of sphalerite, 25.1% of galena and 51.6% of pirrhotite. The rest of chalcopyrite, sphalerite, galena and pirrhotite grains were in the forms of inclusions, impregnations, and simple and complex intergrowths. During the leaching process by sodium nitrate and sulphuric acid solution, it was shown previously that the leaching rate of sulphide minerals decreased with time while a part of the sulphide minerals remained in the leach residue. After leaching at 80°C for 120 min, the yields were 69.8, 82.7 and 67.1% for Cu, Zn and Fe, respectively. Lead, in the form of insoluble anglesite, remained in the leach residue. In addition to the anglesite, unleached sulfide minerals and quartz, elemental sulfur was found in the solid residue. The content of sulphide minerals was 35% of which 33.7% minerals occur independently. In specific, 54.7% of chalcopyrite, 31.9% of sphalerite, 8.2% of galena and 37.6% of pyrrhotite appear as separate grains with highly corroded surfaces. Therefore, the structural assembly of sulphide grains in the polymetallic concentrate is favourable and it is not the reason for the observed decrease in the leaching rate in the final process stages. The obtained findings may be explained by the presence of elemental sulphur that is formed during the reaction and precipitated at the grain surfaces, thus creating a diffusion barrier for the leach solution. [Project of the Serbian Ministry of Education, Science and Technological Development, Grant no. TR34023]

The 6000 series alloys belong to the group of aluminium alloys that contain magnesium and silicon as their two main alloying elements. In addition to these two alloying elements, the alloys contain manganese and other elements, in accordance to the type of alloy. Alloys from this series belong to the group of aluminium alloys which are susceptible to thermo-mechanical treatment. These alloys exhibit the best mechanical and physical properties when they are artificially aged, with the occurrence of the strengthening β'' phase. The process of ageing includes solution heat treatment, quenching and ageing at predefined temperatures for a specified amount of time. All the aforementioned processes have a direct impact on the physical and mechanical properties of the alloy following the performed thermal treatment. In this paper the influence of the temperature of solution heat treatment on the properties of two aluminium alloys belonging to the 6000 series was examined, EN AW-6060 and EN AW-6082. The samples were examined at five different temperatures varying from 510-590°C. In order to examine the influence of the temperature of solution heat treatment, measurements of the hardness and electrical conductivity of the samples were performed, following adequate thermal treatment. After the testing, analysis of the results showed that with the increase of the temperature of soluble annealing, there occurred an increase in hardness, and a decrease in electrical conductivity in the aged samples, due to a better homogenization which caused a better distribution of metastable phases.

Copper is one of the main alloying elements for aluminum casting alloys. As an alloying element, copper significantly increases the tensile strength and toughness of alloys based on aluminum. The copper content in the industrial casting aluminum alloys ranges from 3,5 to 11 wt.%. However, despite the positive effect on the mechanical properties, copper has a negative influence on the corrosion resistance of aluminum and its alloys. In order to further improve the properties of Al-Cu alloys they are additional alloyed with elements such as zinc, magnesium and others. In this work experimental and analytical examination of the impact of zinc on the microstructure and phase transformations of Al-Cu alloys was carried out. In order to determine the effect of the addition of zinc to the structure and phase transformations of Al-Cu alloys two alloys of Al-Cu-Zn system with selected compositions were prepared and then examined using scanning electron microscopy with energy-dispersive spectroscopy (SEM-EDX). The experimental results were compared with the results of thermodynamic calculations of phase equilibria.

Besides iron ore, the main raw material of iron and steel production is steel scrap. This paper presents the quality and sources of creation the iron and steel scrap and estimation of their creation in the future. The content of impurities and trace elements to the scrap is very important and influencing to the quality of the obtained steel. Alloyed steel scrap known composition can often be used as an addition to a metal charge for steel production of the desired composition. Considering the steel scrap formation, the three major groups are elaborated: own scrap or circulation scrap, processing scrap and amortization scrap. The balancing model for estimating of steel scrap creation is based on the calculating the coefficients of the generation circulation, processing and amortization scrap, which are used as the basis for successful modelling.

The paper presents DTA/TG results of polymetallic sulphide copper concentrate from the mine 'Veliki Krivelj' (Serbia) at 25-1000 °C. The reaction mechanism at elevated temperatures was proposed. As confirmation to the proposed mechanism, the results of EDXRF and, XRD analysis of the initial sample and the oxidation products at 550 and 950 °C, and the results of SEM/EDS analysis of the initial sample and the oxidation products at 675 ° C were presented. It can be concluded that the oxidation process goes through sulfide oxidation with characteristic exothermic effects, followed by sulfates and oxy- sulfates formation and their. Kinetic analysis of the oxidation process concentrates the test was performed according to the methods of Kissinger and Ozawa in non-isothermal conditions. The results of kinetic studies have shown that the oxidation process in the whole investigated temperature range is located in the kinetic field.

Procedures for copper secondary raw materials processing include two basic stages: pretreatment of the copper waste and its further metallurgical processing. For copper waste pretreatment technology, there are different applied procedures depending on the type of raw material. All operations of pretreatment are influencing the quality of metallurgical processing. For metallurgical processing of raw materials prepared for the purpose of obtaining copper and copper alloys the shaft, flaming and short-drum furnaces, converters and electric furnaces (electric resistant, electric arc and induction furnaces) are used.

Selective arsenic extraction from enargite based complex concentrate from Copper Mine in Bor (Serbia), using sodium hypochlorite as a leaching agent, was investigated in this paper. The aim was to assess the optimal conditions for the most efficient arsenic removal from the investigated concentrate, based on factorial design applied to experimentally obtained data. Five important factors with three factor levels were used as the input variables and experimentally obtained arsenic extraction yield was taken as the output variable. The first and the second final order model equations were obtained. It was found that the leaching temperature had the strongest effect on the arsenic extraction. The strongest positive interaction was between the sodium hypochlorite molar concentration and the stirring speed during extraction. [Projekat Ministarstva nauke Republike Srbije, br. TR 34023]

In this work, the process of the chalcopyrite leaching in sulphuric acid solution was investigated. Sodium nitrate was used as oxidant in the leaching process. Chemical reactions of leaching and their thermodynamic possibilities are predicted based on the calculated Gibbs energies and analysis of E−pH diagrams. The negative values of the Gibbs energy show that all chemical reactions are thermodynamically feasible at atmospheric pressure and in a temperature range 25-90°C. At high electrode potential and low pH values, Cu2+, Fe2+ and Fe3+ ions exist in water solutions. The increase of temperature reduces the probability of Fe3+ ion existence in the system. The chalcopyrite concentrate, enriched in the “Rudnik” flotation plant, with 27.08% Cu, 25.12% Fe, 4.15% Zn and 2.28% Pb was used in the work. XRD and DTA analysis of the concentrate reveals that the sample contains mainly the chalcopyrite with small amount of sphalerite. For the description of the reaction of leaching process the leach residuals, obtained at different conditions, were chosen for XRD, TG/DTA and SEM/EDX analyses. The elemental sulphur and chalcopyrite phases identified in leach residuals confirm our prediction that the elemental sulphur is formed during the leaching process. Accordingly, elemental sulphur is the main product of the reaction, while a minor amount of sulphide sulphur is oxidized to sulphate during the leaching. The sulphur formed during the reaction was precipitated at the particle surfaces, and slowed down the leaching rate in the final stage of leaching process. In the initial stage, the reaction rate was controlled by the surface reaction. The mechanism, latter has been changed into a diffusion controlled one.

Physico-chemical processes that take place during the refining process in the extractive metallurgy of lead, are connected with ternary Pb−Zn−Ag system, which is necessary to study from the theoretical practical and aspects. Such investigation is important from production point of view, because of the phenomena that occur during desilvering of lead which is one of the important stages during lead refining process. Process of lead desilvering binds to ternary system Pb−Zn−Ag, which was the reason for numerous investigations, both from thermodynamic point of view and in terms of testing and determining the phase diagram, bearing in mind the theoretical, and practical importance of knowledge about the processes which are going in investigated system. The paper presents the results of thermodynamic analysis and investigation of phase equilibria of the Pb−Zn−Ag ternary system using the method of thermodynamic predictions and phase diagrams calculations, respectively, and the experimental results of metalography obtained by optical microscopy. Phase diagram of the vertical section Pb−Zn80Ag20 is presented, obtained by CALPHAD calculation methodology, and using PANDAT thermodynamic software, compared to experimental results obtained by DTA analysis. The results show a pronounced break in solubility, which is characteristic for the whole ternary Pb−Zn−Ag system. Also, it can be noticed that the thermodynamic properties follow the behavior of this system, which is expressed through positive deviation of Raoult’s law, pointing to the lack of lead affinity compared to the other two components in the system. The optical microscopy results of the investigated system show the following: - Sample L1 (weight% Pb = 98): the structure of the observed section shows double eutectic (Pbsol+Zn−Agsol) which lies in the base of the primary crystals of lead (Pbsol) - Samples L2−L5: the structure consists of a dual eutectic (Pbsol+Zn−Agsol) and primary crystals Zn−Agsol Also, it can be noticed certain structural inhomogenity, as a consequence of stratification that occurs in the ternary Pb−Zn−Ag system. However the metalography investigation results confirm the results obtained by defining the phase diagram and mutually agree relatively well in accordance with existing literature data.

Life-cycle assessment (LCA) presents a relatively new approach, which allows comprehensive environmental consequences analysis of a product system over its entire life. This analysis is increasingly being used in the industry, as a tool for investigation of the influence of the product system on the environment, and serves as a protection and prevention tool in ecological management. This method is used to predict possible influences of a certain material to the environment through different development stages of the material. In LCA, the product systems are evaluated on a functionally equivalent basis, which, in this case, was 1000 cubic centimeters of an alloy. Two of the LCA phases, life-cycle inventory (LCA) and life-cycle impact assessment (LCIA), are needed to calculate the environmental impacts. Methodology of LCIA applied in this analysis aligns every input and output influence into 16 different categories, divided in two subcategories. The life-cycle assessment reaserch review of the leadfree solders Sn-Cu, SAC (Sn-Ag-Cu), BSA (Bi-Sb-Ag) and SABC (Sn-Ag-Bi-Cu) respectively, is given in this paper, from the environmental protection aspect starting from production, through application process and finally, reclamation at the end-of-life, i.e. recycling. There are several opportunities for reducing the overall environmental and human health impacts of solder used in electronics manufacturing based on the results of the LCA, such as: using secondary metals reclaimed through post-industrial recycling; power consumption reducing by replacing older, less efficient reflow assembly equipment, or by optimizing the current equipment to perform at the elevated temperatures required for lead-free soldering, etc. The LCA analysis was done comparatively in relation to widely used Sn-Pb solder material. Additionally, the impact factors of material consumption, energy use, water and air reserves, human health and ecotoxicity have been ALSO considered including the potentials for dissolution and recycling processes.

The kinetics of realgar (As2S2) oxidation was studied under isothermal and non-isothermal conditions. The obtained values of the activation energy indicate that the process occurs in the kinetic domainwith the realgar particles being converted to As2O3 and As4O6 (g). The very fast reaction rates were limited by the chemical reaction. The kinetic equation was found to be: –ln (1–α) = 4.56 x 103 x e(–8780/T) x t. The proposed reaction mechanism and chemical transformation investigated by ICP–AES, EDXRF and thermal analysis are discussed.

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