(KOZLOV) INTL. SYMP. ON SUSTAINABLE MATERIALS RECYCLING PROCESSES AND PRODUCTS

Precious metals such as gold and silver are a priority in recycling processes due to their economic values. In particular, jewellery workshop wastes which contain free gold and silver particles are considered a very valuable waste. These metals are usually extracted from jewellery wastes via the cupellation method using metallic lead. In this study, a pyrometallurgical method using a mixture of fluxes has been considered to recover gold from floor wastes of jewellery workshops. The process yields a relatively high efficiency in recovery, as well as savings in time and energy with the use of non-contaminating chemicals. The effect of type and flux-to-waste weight ratio on the properties of slag and recovery of gold has been studied. XRD, XRF, and DTA analyses have been used to characterize the wastes and the formed slag and to investigate the effect of slag properties on the recovery. A maximum value of 63.26wt.% was obtained for the recovery of gold without using dangerous chemical such as lead or contaminating processes such as cyanide leaching.

Aluminum dross consists of a heterogeneous mixture of large lumps, fine oxides and metal pieces. Consequently, sampling requires considerable experience and effort. Additionally, the skimming procedure of the melt, the alloy composition, the type of fluxing agent, and the cooling method of the scum all control the amount of free-metal present in the dross [1]. In industrial practice, the formed dross in the Al-smelter is regularly removed and a part of the liquid metal can be squeezed out. Subsequently, the tilting drum furnace recovers most of the aluminum from the scum with the assistance of a crumbly salt slag [2]. Of significant interest is the recovery of the largest possible amount of metallic Al from the dross during the production process by using a dross press. The aim of this work is to compare the press system currently available at an Austrian Al-smelter with a rented dross press. First, an optimized time-distance diagram for the hired press is determined. Thereafter, the masses of recovered metallic Al are recorded for a period of one week. A part of the resulting hot scum of every charge is processed with the existing press, the other part is processed with the rented. As a result, the proportion of recovered Al based on the total amount of dross is determined for both press systems. Furthermore, a comparison in terms of geometry of the press head, economy and appearance of the dross compacts is carried out. The results are of great importance to the Al-processing company as the optimization of the recycling process depends on a higher aluminum output [3, 4].

FLOGEN Decision Making, Control, and Optimization system has been applied in Waltz Rotary Kiln that produces Zn from steel dust. This resulted in simultaneously reducing the specific coke/coal consumption, maximizing Zn yield, decreasing Zn losses in the slag, minimizing accretions and balls inside the furnace, increasing the operational time without stoppages and enabled greater flexibility in using multiple raw materials. This paper presents some of the above results along with the most recent developments of application in other processes

Dust in gas cleaning systems in the process of blister copper production is a waste of class 2 hazard. The accumulation of copper smelter dust may cause significant damage to the environment in the places of their storage. This dust contains considerable contents of zinc, lead, tin, and copper, which makes its use for recovery of these elements possible. There are, however, a number of characteristics such as complex multicomponent composition and high content of halogens. These physicochemical properties of the copper smelter dusts of FL PPM AO Uralelectromed (Russia) and PO Balkhashtsvetmet (Kazakhstan) were studied using chemical, X-ray phase, and electron microscopy methods. In both dust samples, the presence of lead in the form of sulfate and sulfide, of zinc in the form of orthostannate, and of ferrite, sulfide and copper in the form of chalcopyrite was identified. To obtain the intermediate products for the production of zinc, lead, tin and copper in the industrial processing of the copper smelter, dust can be most effectively carried out by the proposed process flowsheet with one pyrometallurgical treatment in a Waelz furnace with further leaching steps.

Nowadays, it is obvious that the share of the hydrometallurgical operations in the global volumes of non-ferrous metals production is gradually increasing [1]. This trend is specific to the Republic of Kazakhstan as well. Rapid development of the copper hydrometallurgy based on the processes of heap leaching (HL), solvent extraction (EX) and electrowinning (EW) resulting in getting highly-pure copper cathodes and economic efficiency has been specific to the country during recent years.
The Eastern mining-and-metallurgical research institute for non-ferrous metals (VNIItsvetmet) has been running the researches on application of HL-EX-EW processes for processing of copper-bearing ores of Kazakhstan deposits since 1997. The heap leaching tests include study of the ores’ material composition, bottle roll and column tests, selection of the optimal extractant for each pregnant leaching solution (PLS), etc. Research results can be used to come up with the feasibility studies, Process Procedures, basic design, and detailed engineering of the ore-processing plants [2].
There is a number of plants operating nowadays in Kazakhstan under HL-SX-EW technology which were designed and constructed on the basis of VNIItsvetmet research results. There are, for example, ore-processing plants at the deposits of Kounrad (annual capacity of 13 thousand tons of copper cathodes), Ayak-Kodzhan (annual capacity of 3 thousand tons of copper cathodes), Aktogay (annual capacity of 15 thousand tons of copper cathodes) and others [3].

Raw materials containing zinc, processed at the Chelyabinsk Zinc Plant, has considerable content of lead. According to the Plant technology, lead is recovered in a lead cake (40-45% of Pb)-solid residue from Waelz-oxide leaching. Lead is contained in cake in sulfate form.
Application of PbCO₃, containing raw materials in lead production allows to decrease the flux consumption, and yields dump slags and SO₂ discharges with gases during smelting in short-drum furnaces. Carbonization of lead can be carried out by processing the sulfate zinc cake by using a hot solution of Na₂ CO₃. It is reasonable to carry out the lead cake carbonization in hydrometallurgical production conditions.
For the purpose of the mastering of carbonization of the whole amount of obtained lead cakes in the Chelyabinsk Zinc Plant, the laboratory carried out experimental-industrial testing with definition of optimal carbonization modes.
Analysis of the product obtained during testing has shown that it contains 76% of PbCO₃ and 11% of complex hydrocarbonate of lead and sodium.
For the purpose of obtaining a required quality marketable product (40% of Pb, 9% of Zn, 2% of Na, and 4% of S), the following measures are required: maximal extraction of Zn in solution on the stages of Waelz-oxide leaching, preliminary washing of sulfate cake from acid and water-soluble sulfates, and the washing of carbonized product from Na2SO4.
On the basis of experimental results, the the technological and apparatus scheme of the process was developed.

Modern experimental material has given reason to believe that the key points in the development of scientific concepts about the nature and mechanism of physicochemical processes are the following provisions of M Faraday: the identity of energy manifestations in the interaction of material objects and the discrete nature of electric current. Developed without taking into account the work of M. Faraday, the theory allowed not to take into account the identity of energy manifestations in the interaction of material objects. Hence, there was a lack of work to determine the real mechanism of heat transfer between material objects. This circumstance influenced the lack of attention to the use of the discontinuity of electric current for practical use. We have shown that a change in a wide range of electrical signal parameters can promote unusual chemical reactions and physicochemical processes at the interface and in condensed systems. Phase transitions in an oxide melt can occur without noticeable thermal effects. That is, the structure of this liquid does not only depend on the chemical composition and temperature. Under the influence of electromagnetic fields, the conductivity of the melts may decrease with increasing temperature and change at a constant temperature. Crossed electromagnetic fields cause phase and quantitative division of melts of both synthetic oxide melts, and oxide-sulfide multicomponent systems, etc. The possibility of dissolving metallic molybdenum in alkaline solutions has been established experimentally. The dissolution rate is not proportional to the frequency of the current and the dissolution stops as the current frequency increases. Dissolution ceases at any current parameters and concentrations of potassium oxide at temperatures above 75 ^oC. The dissolution of molybdenum does not occur at any current parameters if the concentration of potassium oxide exceeds 9%. It was shown that the electrical signal at the metal aluminum / aluminate solution interface accelerates the decomposition of the aluminate solution by at least 4 times (in some cases, from 45 hours to 8 hours). Studies have been conducted on the use of a sulfurgraphite composite electrode for organizing a parallel process for the formation of a leaching agent (sulfuric acid, sodium thiosulfate, etc.) and for the extraction of metals into a solution from various metal-containing raw materials. These and our other experimental data can serve as a basis for revising some theoretical concepts in the natural sciences and creating effective technological processes.

One of the resources in the production of non-ferrous metals is use of waste iron and the steel industry, in which the content of non-ferrous metals are kept up to industrial conditions. Thus, in dusts of gas purification of some plants of ferrous metallurgy, the zinc content is as high as 15%. The results of the study of the binder agent effect during the briquetting of charge include the type of the carbonaceous reducing agent, the consumption of reducing agent, and the fineness of charge components on the process of carbothermal reduction of zinc from oxidized zinc ore with the addition of stale dust of gas cleaning of blast furnace smelting. Bentonite, hydrated lime, and treacle were tested as a binding agent during briquetting of charge. It is established that the optimum binding agent is treacle in an amount of 4.5-5.0% by the weight of the ore. It is shown that the residual zinc content in a product of the reduction roasting, when using the special coke received from coal of Shubarkol, deposit is 1.9 times less than when using anthracite. It is also 3.3 times less than when using metallurgical coke, i.e. special coke is the most fissile reducing agent. The carbon consumption during carbothermal reduction of zinc from oxide ore with the addition of dust is 22-24% lower than in case of zinc recovery from ore. It was found that crushing of charge to class + 0.071-0.04 microns reduces the degree of zinc sublimation. If the size of the charge is 1.0 microns, then the residual zinc content is increased in the cinder. High recovery efficiency is achieved with the following composition of charge, wt. %: oxidized zinc ore is 53.8; dust of gas purification of blast furnace smelting is 26.9; special coke is 21.0; treacle is 5.3.

Lead is one of the metals that are included into the material production area multiple times because its losses during industrial operations are minimal. That is why the fraction of secondary lead in overall lead production is high. The secondary lead production in the world amounted 55.8 % of the overall amount of produced metal [1, 2].Development of the nuclear industry requires an increased amount of production of pure lead and Pb-Bi alloys of desired composition to be used as liquid metal heat carriers [3]. To obtain pure metallic lead from secondary materials, the method of electrochemical reduction of metallic lead from chloride melts was used [4]. The equilibrium potentials of the pseudo-binary liquid metal Pb-SbBi system was measured in the KCl-PbCl melt in the temperature region of 723–893 K. The thermodynamic characteristics of the Pb-SbBiij system in the liquid state were calculated [5]. To develop the technology of the electrolytic lead obtained in molten chloride systems, it is important to understand the mechanism of the processes that take place in the liquid metal electrodes. There is a lack of information on the liquid metal electrode solubility in the Bi-Sb-Pb alloys in the KCl-PbCl melt. The anode dissolution of alloys was studied by the current cut-off from the stationary conditions in the galvanostatic regime using a galvanostate–potentiostate IPC-Pro. The influence of the liquid metal bismuth-antimony-lead systems on the anode polarization in the molten lead and potassium chloride mixtures is established. According to the form of the concentration dependence of polarization curves, we assumed that the anode process in the liquid metal alloys in the KCl-PbCl₂ (50-50 mol. %) melt has a diffusion character. The parameters of electrochemical lead obtained from secondary materials were determined.

Recently an innovative, patent pending reactor system based on the PBET method [1] (LABQA-RSGB), which simulates the human gastrointestinal tract, was developed and metal bioaccessibility was evaluated for mining waste solid samples [2]. Results obtained with this system are on par with those of US EPAs equipment from SW-846 Test Method 1340 [3].
The LABQA-RSGB system simulates stomach and small bowel conditions, while allowing for monitoring, pH adjustments and development of kinetic studies without interrupting the process nor altering the reactors’ temperature.
The current paper describes the improvements carried out on the LABQA-RSGB, in order to minimize systematic errors and potential sources of cross contamination, as well as allow design and reactor operation optimization [4]. Results of the bioaccessible fraction extracted with the new equipment (LABQA-SRSGB) were compared with those of the original LABQA-RSGB and US EPA equipments, using a reference material, internal controls and samples.
Coupled with continuous and simultaneous monitoring of pH, temperature and stirring within each reactor, the enhancements implemented in the LABQA-RSGB provide reliable results for various potentially toxic elements in different matrices.

The Institute of Chemistry and Chemical Technology (Siberian branch of the Russian Academy of Sciences) designed new "mixer-settler" type of extractor ESOT - 1.0 -15.0 (poly-propylene) and ESOT -0.8-5.5 (polyethylene with titan turbine type mixers). In 2013, these extractors were installed and tested in the indium extraction department of the hydrometallurgical shop of the Chelyabinsk Zinc Plant.
The modernized extraction unit is a cascade of three extractions (ESOT - 1.0 - 15.0) and six re-extractions (ESOT - 0.8 -5.5) which are sequentially connected blocks. Production capacity of the unit is 15m³/h of solution, counted as total volume of both phases.
Extractor ESOT - 1.0 - 15.0 is designed for indium extraction from sulphate-chloride acid solutions in raised temperatures (about 600°C) with a wide productive capacity range (max.15 m³/h of solution as total volume of phases). Extractor ESOT - 0.8 -5.5 is designed for the processes of indium re-extraction and extracting agent washing. Its production capacity does not exceed 5 m³/h of solution, counted as total volume of phases.
Application of the units ESOT - 1.0 - 15 and ESOT - 0.8 - 5.5 made it possible to carry out the following measurements:
- Efficient extraction in a wide range of the unit productive capacity (3-8 m³/h) of water phase with organic to water phases ratio of 1:3 (not counting recirculation of organic phase);
- Minimization of bilateral carry-over of water and organic phases (organic phase carry-over with raffinate was 0.2-0.5%, while water phase carry-over, saturated with extracting agent, was less than 0.3%);
- Minimization of indium loss with raffinate (to 6-7 mg/l with productivity 5 - 7.5 m3/h of water phase);
- Ensuring the reliable performance of the extraction unit with higher silica acid concentration in the initial solution (to 0.4 g/dm3);
- Consumption decrease on the unit production (cost decrease of basic materials by more than 10 times);
- Maintenance simplification and extraction unit repair.

Currently, a number of countries are developing new nitride (UN-PuN) fuel for fast-neutron nuclear reactors [1]. At the same time, methods for nitride SNF processing are developed. These methods are proposed to abandon water technologies in favor of pyrochemical methods, which use molten salts [2, 3].
As nitrides are electronically conductive, an initial opening of nitride SNF was suggested to be performed by electrochemical dissolution with the transfer of SNF components into the molten LiCl-KCl eutectic. It turned out, however, that the reaction UN - 3e = U³⁺ + 0.5N₂↑ is accompanied by the UNCl formation reaction. UNCl is an insulator, it covers the anode and dissolution stops. Currently, the research is suspended.
Another method is “soft” chlorination (i.e. without chlorine gas). In the (LiCl-KCl) _eut. melt, the following reactions are possible:
UN + 1.5CdCl₂ = UCl₃ + 1.5Cd + 0.5N₂ ΔG = -60.6 kJ/mol at 500°C (1)
PuN + 1.5CdCl₂ = PuCl₃ + 1.5Cd + 0.5N₂ ΔG = -149 kJ/mol at 500°C (2)
Experimental verification, however, revealed that at 500 0C the reactions of formation of a number of other stoichiometric and non-stoichiometric nitrides - UN_1.5, UN_1.55, UN_1.5, UN_1.55, UN_1.69, UN_1.74, UN₂ and UNCl proceed along with reaction (1). The UN → UCl₃ conversion degree is ~ 30%. The rest of the uranium was found as a black precipitate that consisted of a mixture of UNCl and various nitrides. Using thermodynamic modeling, it was determined that, at a temperature of 750°C and above all nitrides, including UNCl, dissolve in an excess of CdCl₂ to form UCl₃. The experiment confirmed the calculation results completely. It was also found that the CdCl₂ substitution by PbCl₂ allows reduction of the process temperature to 650°C, but in this case, a UCl₃ + UCl₄ mixture forms.
Another likely the first stage of the nitride SNF processing can be voloxidation, i.e. conversion of all nitrides to oxides by heating in air. For example, the uranium oxidation chain is as follows:
UN → (U₂N₃+UO₂) → UO₂ → U₃O₇ → U₃O₈ → U₂O₆ (gas) (slowly)
An important advantage of this approach is that we obtain a universal process suitable for processing both nitride and oxide SNF.

As a means of addressing global warming, the world is increasingly turning to the use of Li-ion batteries in electric vehicles and as storage batteries in the home. Therefore, there is a growing need for Li. I propose a method for recovering Li from used Li-ion batteries by using innovative dialysis, wherein Li only permeates from the positive electrode side to the negative electrode side through a Li ionic conductor functioning as a Li separation membrane (LISM). Measurements of the Li ion concentration at the negative electrode side, as a function of dialysis duration, showed that the Li recovery ratio increased to approximately 8.6% after 72 h with 5V applied electric voltage. Moreover, other ions in a solution of used Li-ion batteries did not permeate the LISM.
Figure 1 shows the proposed Li recovery method. This innovative method involves the use of an LISM whereby only Li ions in a solution of used Li-ion batteries permeate from the positive electrode side to the negative electrode side during electrodialysis; the other ions, including Co, Al, and F, do not permeate the membrane. Li_0.29La_0.57TiO₃ was selected as the LISM. The positive side of the dialysis cell was filled with used Li-ion battery solution. Then the negative side was filled with distilled water. The applied dialysis voltage was 5 V, and electrode area was 16 cm². The Li recovery ratio increased with electrodialysis time. Then, Co, Al, and F were not permeated.
After electrodialysis, CO₂ gas was bubbled in the Li recovery water to produce lithium carbonate (Li₂CO₃) as a raw material for Li-ion batteries. The Li₂CO₃ deposition was easily generated by the reaction of CO₂ gas and the Li recovery solution as a lithium hydroxide (LiOH) solution (Fig. 2).

This article gives the results of the mastering of the technology of Waelz oxide calcinations in rotary furnaces in the Chelyabinsk Zinc plant. A flow hardware diagram is shown together with calcinations process modes.
Waelz oxide calcinations technology includes the following measures: pelletizing of powdered oxide into pellets, calcinations in pipe furnaces, pellet cooling, milling of calcined oxide in ball-rod mill, gas cooling, and cleaning with secondary fumes' recovering. Calcined products are prepared to be leached, while secondary fumes are washed with sodium carbonate and water from chlorine and fluorine.
Calcination is carried out in oxidizing the atmosphere at the temperature of 900-1100C for efficient removal of halides and oxidation of iron (II), arsenic, and metal sulfides. Residence time of the material in high temperature zones is not less than 2 -3 hours.
The calcinations technology, mastered in the Chelyabinsk Zinc plant, allows the carrying out the following measures:
- Removal of Waelz oxide halides (up to a residual content of Cl-0.06% and F-0.01%);
- Oxidation of Fe (II) and As, reduced their passing into solution during Waelz oxide leaching;
- Increase of solubility of zinc (up to 91%) and cadmium (80%) in Waelz oxide, simplifying its leaching technology and reducing metal loss;
- Reduction of material amount approximately by 2 times, increasing the leaching flowsheet productivity.
As a result of the calcinations technology, the shop processing Waelz oxide efficiency was increased by 33-36%. The wash water volume is 15-20 times lower during secondary fumes washing than during Waelz oxide washing, and the obtained solution is suitable for concentration and evaporation.

The objective of the work was a model analysis of possible methods to decrease the consumption of carbon energy resources and associated emissions of CO₂ into the atmosphere during fuming and Waelz processing of zinc-bearing middlings. The METSIM models of fuming process for zinc slag from lead smelting and Waelz process for the charge, based on zinc residues of electro-lytic zinc operation, were developed by the authors and used for this analysis. Adaptation of models to the data of industrial processes made it possible to use them for the analysis of options to decrease energy consumption and CO₂ emission with changes in operating parameters of the studied processes. According to the model analysis, carbon consumption and CO₂ emissions into the atmosphere during zinc slag fuming can be decreased when the blast is heated and the O₂/C ratio is decreased, while oxygen enrichment of the blast is inefficient. During the Waelz pro-cessing of charge, based on zinc residues, the highest estimated effect in carbon energy resources saving is achieved by the use of additional oxygen blasting and heated air blasting with associat-ed decrease in air suction into the kiln from the atmosphere. Thus, the model analysis made it possible to compare and optimize various options to decrease the consumption of carbon energy resources and CO₂ emission into the atmosphere during processing of zinc-bearing middlings.

Gas cleaning dusts, forming in ferrous and non-ferrous metallurgy, have a high content of zinc, lead, copper and other components. These metals may be extracted from steel electrosmelting dust and copper smelting dust for matte into the intermediate products for their production. In the Russian Federation (RF), steel electrosmelting dusts, containing 30% or more of zinc [1], began to be recycled only in recent years [2]. Millions of such dusts disposal tonnes have been accumulated. Copper smelting dust for matte contains 10-25% of zinc and 10-30% of lead that makes it perspective for non-ferrous metals recovery [3]. The technological flowsheets of metallurgical dusts processing of steel and copper production are given in this work at the conditions of Chelyabinsk Zinc Plant, PJSC. The main flowsheet with intermediate products obtaining for zinc, lead and iron production, as well as an auxiliary flowsheet with zinc powder and lead fumes production are presented for steel electrosmelting dust. Both flowsheets are presented for coper smelting dust: a functional flowsheet with two pyrometallurgical stages with intermediate products obtaining for zinc, lead, tin and copper production and a developed flowsheet with one pyrometallurgical stage. The valuable components extraction from wastes of steel and copper production contributes to increase the economic and ecological efficiency of production in the nonferrous-metals industry by means of raw materials economy and implication in recycling of resulting and non-utilizable wastes.

The selective recovery of valuable metals from metal-containing residues not only conserves the primary resources, but also improves the availability of raw materials. First and foremost, the focus must be kept on previously unrecycled wastes as these have been removed from the circular resource flow.
The recycling of used batteries effects not only the treatment of hazardous waste, but also the recovery of valuable elements used in this field. On the commonly used pyrometallurgical route, mostly only the main metals are recovered. The application of hydrometallurgy remedies this problem and is mentioned in various research papers [1]. This process route gives the possibility of recycling for materials such as rare earths, cobalt and nickel which are often slagged in the pyrometallurgical process [2]. The recycling of metal-containing residues from the battery sector by hydrometallurgical means offers a wide range of possibilities. It is assumed that many different residues, as well as nickel-cadmium or nickel-metal hydride batteries and lithium-ion batteries can be recycled. Recycling processes for these metal-containing residues are divided in chemical processes (leaching, selective precipitation, solvent extraction) and mechanical and/or thermal processes [2,3].
The optimization of leaching parameters in the field of recycling of metal-containing residues represents a complex topic in the literature. In addition to the selection of an appropriate leaching medium, the variation of different leaching parameters such as temperature, time, solid-liquid ratio and concentration of the leaching medium have to be investigated in order to obtain the best possible result. Efficient leaching can only occur if there is an optimized process window with upper and lower limits for the respective parameters [4]. For experimental design and evaluation, a statistical software for design of experiments based on a fully factorial model serves for the interpretation of the process area [5].

Iron and steel making is accompanied by generations of various types of by-products and waste materials which usually need some pre-treatment to be usable [1]. The resource efficiency, environmental, and economic benefits are vital keys to motivate the re-circulation of steel mill residues and recovery of their associated minerals as far as possible to save the virgin resources and reduce material sent to landfills. Nowadays, the steel industry pays more attention to adopt a circular economy model to reach zero waste through reuse and recycling of all by-products. In this context, briquetting can play an important role in residues re-circulation in the steel industry and circular economy [2-5]. The developed briquettes should have adequate chemical composition and mechanical strength to be suitable for usage in iron and steel production units [6, 7]. In the present study, the residues rich with lime and metallic iron are selected for developing briquettes suitable for basic oxygen furnace (BOF) implementation. The briquetting is performed with binders which have low sulfur content to enhance the recycling efficiency. Various recipes are designed and produced using lab scale hydraulic press and pilot scale roller press. The mechanical strength of the developed briquettes is evaluated using cold compression strength device and drop test. The potential of the developed briquettes on saving lime and scrap will be addressed. The gained knowledge can contribute to the enhancement of residues re-circulation in other metallurgical sectors.

The Chelyabinsk Zinc Plant developed the technology of processing of zinc-, lead- and tin-containing copper industry dusts, including the following stages:
-Pyrometallurgical stage: calcinations with addition of sulphidizer, flux and reducing agent to the product, where lead is removed from the product with transfer in processed sublimates, while zinc and tin stay in cinders;
- Hydrometallurgical stage: high-temperature leaching of cinder, where zinc, iron, copper, etc. are extracted in solution during the obtainment of tin-concentrating solid residue.
Here we consider the hydrometallurgical stage of obtaining of tin-containing concentrate from cinder with low content of lead (less than 1%).
Here is shown the low extraction of zinc in solution and absence of selective separation of tin and lead with acid sulfuric-acid dust leaching without application of the pyrometallurgical stage.
There-stage leaching (similar to the technology of hydrometallurgical processing of Waelz-oxides, existing in Chelyabinsk Zinc Plant) and one-stage high-temperature leaching were researched for obtaining cinder. Three-stage product leaching is low-efficient, because it requires a lot of equipment and does not provide the required concentration of tin in solid residue.
About 98% of zinc contained in cinder, and more than 95% or copper and iron is transferred in solution during the high-temperature product leaching by waste zinc electrolytes with addition of sulfuric acid (t= 80-90°C, concentration of H₂/SO₄ is 160-170g/dm³). The obtained solution is required for application in the technological cycle of the zinc plant. Solid residue contains 14-21% of tin, which allows its use at tin enterprises.

The rotary kiln process that produces magnesite sinter creates a considerable amount of dust that contains up to 96% MgO [1]. Usually the quantity of the produced dust is 16% of the quantity of the magnesite concentrate charged in the Rotary Kiln. Up to now, about 90% of the dust is recycled with the feed of the Rotary Kiln, while about 10% of this quantity is lost with the gas.
The quantity of the dust recycled creates various problems in the Rotary Kiln such as process disturbances, creation of accretions that decrease the active volume, and decreases in the productivity of magnesite sinter.
Another alternative is to stop dust recycling in the Rotary Kiln and use it as a raw material to produce magnesium sulphate in a separate unit after the dedusting chamber.
Eliminating dust recycling in the Rotary Kiln will improve the stability and efficiency of the process, increase the production rate since new magnesite concentrate will be charged in the feed instead of the dust, and significantly decrease the production cost of the magnesite sinter. The magnesium sulphate produced in this way will also constitute a new marketable product that will increase the profit of the company.
In this paper, the production of magnesium sulphate using the magnesite sinter Rotary Kiln dust as a raw material will be studied and evaluated and the best production technology will be suggested while, in a subsequent publication, a description of the project on building and commissioning of magnesium sulphate production unit and its process will be described.

Technologies are getting more complex each day and with that the metals and alloys utilized are getting more specialized and unique in their composition. This in turn leads to an increase in the importance of the so-called high-tech metals [1]. Many such valuable elements are only produced as a by-product of another carrier metal in the absence of the specific minerals mined for their primary production. These minor, rare, valuable or special metals, however those technologically important hitchhikers are labelled, gained their importance in the last few decades [2]. As a result, they recently caught the attention of the recycling industry and as a consequence, industrial residues were landfilled for decades and by-products, as well as intermediate process streams, are still generated today without extracting these elements. A striking example of this is the iron precipitation "jarosite residue" from the hydrometallurgical zinc industry, which is the investigated material described in this paper.
As a result of low zinc and lead contents, a targeted economic recycling of this material also has to take into account the present minor elements, such as indium and silver. In this context, a pyrometallurgical process is investigated which recovers zinc, indium and silver simultaneously as a dust product and the iron, as an alloy. The technology investigated is a reductive vaporization step, exploiting the selective formation of volatile compounds especially of Indium and Silver by the addition of a chlorine carrier [3]. Therefore, the paper summarizes the fundamentals, such as morphology of jarosite and required pre-treatment of the material, to allow the formation of volatile indium- and silver-compounds.

The present study describes a zero discharge hydrometallurgical process for value addition of non-metallic LD Slag fines to multiple products of industrial importance. The process involves the quantitative separation and conversion of calcium along with some key nutrient elements which are part of LD Slag fines. This includes magnesium, iron, phosphorus, and manganese, which are used to form a new chemical compound viz Limegyp (Registered trade mark product) which finds application in the field of agriculture as a multi-nutrient soil conditioner. At the same time, the authors have also converted calcium into an insoluble anhydrite containing silica. The significance of the process lies in producing two types of products at the same time. One of the advantages of the process is that there is no generation of any type of gas or liquid pollutants. Hence it is strictly a zero discharge process which has enormous significance in the current global scenario. Another advantage of the process is that it reduces the recycling of LD Slag fines into iron making, thus limiting the entry of elements like phosphorus, alumina etc., in the steel making process. This innovative process is applied for patent vide Indian patent application No: P||1077||4||2019[1]. The present study further describes chemical and mineralogical characterization by different techniques such as ICP-OES Analysis, XRD, FTIR and Raman study.

Provision of a stable and regulated process is an urgent task during the processing of sulphide zinc concentrates with different chemical and particle size composition in fluid-bed furnaces. This problem is solved by choosing temperature conditions of roasting, and calculation of the charge composition as a mixture of various zinc concentrates.
The current trend in the change of zinc concentrates’ grain-size composition (average particle size decrease) and the increase of impurities of iron, lead, copper, and silica contained in them determines the necessity of the studies on the concentrates sintering ability during calcination, which is undesirable for the process in fluid-bed furnace.
The article considers the effect of particle size composition on the probability of agglomerative sinter formation during calcination and the effect of impurities in the concentrates on the strength of the received sinters. The threshold particle size of the concentrates (100 µm) was defined. If the threshold particle is less than 100 µm, then agglomerative sinter is formed in the process of roasting. In the roasting process of different concentrates with fixed values of particle size, temperature and time agglomerative sinters with different mechanical strength were obtained. Dependence of the sinter strength on the iron content in the concentrate from 20 kPa at 1.43 % Fe to 540 kPa at 14.85% Fe was determined.
Changes were made in the process of calculation and charge preparation for calcination in fluidized bed furnaces. Changes were also applied to the furnace design on the basis of current and previous researches. These changes made the prevention of adverse effects of the foregoing factors possible and ensured stable technology management.

Formation of skulls is one of the main disadvantages of the processes carried out in rotary kilns (productivity decrease, process chemistry violation).
Analysis of the skull formation process reveals the main causes of their growth:
-chemical composition of charge mixture (containing slag-forming compounds: CaO, SiO2, FeO);
-kiln rotation speed;
-feed material quantity;
-temperature conditions;
-grain size composition of charge mixture.
Setting operating conditions of rotary kiln in accordance with charge material composition makes it possible to avoid skull formation.
At the same time it is necessary to make the skull-formation in kiln as a means of the furnace refractory protection from chemical and thermal “corrosion”.
It is possible to solve the problem of the furnace operation without any skulls and refractory time facing more than 12 months by operating rotary kiln in variable silica ratio mode:
- Period 1, silicate unit (C/S) – 0,4 – 0,6 (skull is not formed). Duration is 2-4 days. Skull is removed if the furnace operation is more than 4 days;
- Period 2, silicate unit (C/S) – 1,4 – 1,6 (skull is formed). Duration is 1 day. Skull can be increased if the furnace operation is more than a day.
Provision of operation mode requires the variable silicate module:
- installation of thermal imager, controlling the furnace body temperature, which allows to estimate the skull thickness;
- repeating the furnace operation with the silicate module 1,4 - 1,6.

Tantalum rich ores containing oxidic minerals like tantalite or columbite are primarily mined by artisanal and small scale practices. [1] Major sources located in countries around the African Great Lakes like Congo and Rwanda control global output with a 60 % share. [2] Direct treatment of concentrates with a Ta₂O₅ content higher than 25 % takes place via leaching followed by liquid-liquid extraction. Recycling, chlorination and processing of low grade residues, slags, sludges or dusts represent aspiring alternatives accounting for approximately 30 % of the tantalum world production. [3] The pyrometallurgical manufacturing of synthetic tantalum concentrate (syncon) in a multi-stage process constitutes an established procedure for various input materials. [4] Within this study, the first step (smelting and reduction) is recreated in a small scale induction furnace as well as a DC-EAF. Huge amounts of high melting slag comprising mostly Al₂O₃, CaO, MgO, SiO₂, TiO₂ and ZrO₂ arise whilst Nb and Ta concentrate in the metal phase. Previous flow behaviour investigations [5] and viscosity calculations reveal low viscous slag to be crucial for good metal/slag separation at elevated CaO content. Therefore, a variation of slag basicity is tested for further process optimization and to attain technical standard regarding treatment time, tapping procedure and slag composition of < 0.2 % Ta₂O₅. Accumulation of value components was successfully realized and validated by SEM/EDX. Thus, yield, energy saving potential and other process adjustments for the syncon production can be investigated at the laboratory scale before upscaling to industrial quantity.

The purpose of our work was the application of instrumental and analytical methods for studying of changes that happen to plastic materials during the recycling process and the way they are affected by the additives. The research covered the studying of plastic materials microstructure, the specification of additives and the change of principal physical and mechanical properties during the recycling process.
The plastic materials analyzed were polyethylene PE, polypropylene PP and polystyrene PS. As recycling process we used extrusion in industrial scale. For the studying of microstructure were used infrared FT-IR and Raman spectroscopy methods and scanning electronic microscopy SEM, equipped with energy distribution system EDS for the qualitative analysis of chemical elements. Moreover we used X-ray diffractometry method to study the crystalline structure and the ability to determine the additives when they contained more than 5% of the total mass. Among the physical properties determined were specific gravity, density, melt flow index MFI, viscosity and average molecular mass. Mechanical properties were determined on polymeric rods with different diameters using the tensile test in one direction. The results obtained show the structural changes and the physico-mechanical properties during the recycling process and the influence of additive on them.

The objective of the work was to study the capabilities of the efficiency arsenic removal from the lead dusts which are either generated by the copper smelters or removed from lead operation cycles. Arsenic removal issue is the vital problem to be solved to get the dusts involved into the processing operation [1]. According to the sources, sulphatisation of the dusts with sulphuric acid at the temperature of 300-400°С is the most efficient way to get arsenic removed. In terms of arsenic removal rate and leaching agent consumption, the sulphatisation process is more efficient method in comparison with direct sulphuric leaching [1-3]. That is, it is predetermined by the fact that lead dusts contain arsenic compounds which are hardly soluble in sulfurous solutions, but get transformed and fumed into the gas phase at the increased temperatures specific to sulphatisation process [1].
Arsenic transition to gas phase using conventional dust sulphatisation process, however, requires both increased power consumption and installation of the complex systems to collect and utilize the fumes. That makes the sulphatisation process less environmentally friendly than direct sulphuric leaching. Besides, conventional sulphatisation process is less efficient in terms of lead, copper, and zinc recovery degrees.
The possibility to combine advantages of both the sulphatisation process and direct sulphuric leaching of the dusts without arsenic sublimation to gas phase was studied within the paper. It was found out that high degrees of arsenic, copper, and zinc recovery to the solutions could be achieved at a decrease of the sulphatisation process temperature to 100-150°С. This provides high quality of the lead products and prevents arsenic fuming. Further, processing of the product solutions including arsenic and valuable metals recovery to final products can be performed using commonly known methods [3-4].

We will present the Raman microspectroscopic detection of bornite [Cu₅FeS₄] -, chalcocite [Cu₂S] -, and covelitte [CuS] - bacterial interactions by Sulfobacillus thermosulfidooxidans. The absorption signals of amide I, K⁺-jarosite [KFe₃(SO₄)₂(OH)₆] and of the produced extracellular polymeric substances (EPS) from Sulfobacillus thermosulfidooxidans as a function of position on the surfaces of the bioleached bornite, chalcocite and covellite demonstrated their heterogeneity within the surface of the minerals. We will present a direct contact mechanism for the bioleaching of bornite [Cu₅FeS₄] -, chalcocite [Cu₂S] -, and covelitte [CuS]. [1-2]
Raman data were collected by a LabRAM from HORIBA Jobin Yvon equipped with a CCD detector. It is equipped with an Olympus BX41 microscope 50x. The 441.1 nm excitation laser beam was provided by a Helium-Cadmium laser. The laser power incident on the sample was 20 mW and the accumulation time 15-20 min for each spectrum.

We report for the first time the v(Cu-S) of bornite and chalcocite which are intermediates in the bioleaching of chalcopyrite and the bioleaching behavior of bornite, chalcocite and covellite with the bacteria Sulfobacillus thermo sulfidooxidans by Raman microspectroscopy and compare it with that previously reported for chalcopyrite. [3-4]

This paper discusses the results of the research carried out on the pilot zinc production wastewater treatment unit. The first stage of the pilot trials is chemical treatment of wastewaters (using reagents) and their concentration on the reverse osmosis unit. Deficiency of sulphurous zinc materials shows the need to engage recycled material in processing. During the recycling process, secondary raw materials are cleaned from impurities derived by sewage. Chlorides, sulfates and sodium fluorides are the main impurities removed by sewage. Standard limestone technology of wastewater treatment doesn't allow the possibility to remove the foregoing soluble impurities from the wastewaters. Return of wastewaters to the process isn't possible due to the harmful effect of sulphates, chloride, and fluoride on the process of zinc extraction.
Developed technology of the wastewater treatment allows use of the purified water in industrial production and directs the concentrate acquired from reverse osmosis to evaporation.
Optimal conditions and parameters of the following processes are defined:
- Chemical treatment of wastewater (adding reagents): рН = 11.3-11.6; residual hardness-less than 1.0 meq/l; heavy metals precipitation degree comprises 93-98.9%;
- Ultrafiltration: transmembrane pressure - 0.6 bar, partition coefficient - 85%; filtration rate - 375 l/m²h; filtrate turbidity - 0,6 NTU;
- Reverse osmosis: concentration of soluble salts using two-stage reverse osmosis (in the concentrate) is 2.27 mg/dm3 (at pressure on the 1st stage is 48-52 bar, on the 2nd _ 60-64 bar), total concentration of salts in the permeate is 27.4 mg/dm³

Apart from metals, the mining and metallurgical processing of non-ferrous metals such as Cu, Pb, Zn, Au, Ag produces large volumes of waste [3]. A particular challenge is generated by waste containing residual sulphides, like pyrite, as sulphides can, upon oxidation, cause so-called acid mine drainage. This paper presents the results of experiments for advanced removal of sulphur in order to obtain near zero-waste and valuable metals products as well as other by-products [5].
The main process applied is leaching under pressure in an alkaline media (K₂CO₃, Na₂CO₃, KOH, NaOH) using air or oxygen at low to moderate temperatures and pressure (120-155^oC and 4-8 atm.) [1-2][4].
Results show that more than 96-99% of sulphur can be removed by leaching of pyrite in one stage while from an alkaline solution (coming from pressure leaching), pure crystals of K₂SO₄ / Na₂SO₄ were obtained as valuable by-products.
This paper is part of the NEMO project which has received funding from the European Union, EU Horizon 2020 Programme under Grant Agreement No. 776846 - https://h2020-nemo.eu/.

The Chelyabinsk Zinc Plant carried out the pilot tests of flotation technology removal of sulfur from zinc cake on pilot pneumatic flotation machine CFM-180. A key principle of the operation of pneumatic machines CFM is pulp oxygenation with finely dispersed air bubbles in the ejector, which reduces flotation time and increases its selectivity.
Technological schemes of testing include basic flotation of original cake, control flotation of the chamber product, and two cleaner flotations of froth product.
In comparison with mechanical flotation machine, the following indicators increase during flotation of cake on CFM:
- Initial feed performance (by 4 times);
- Sulfur recovery into flotation concentrate (by 1.4 times);
- Silver recovery into flotation concentrate (by 1.2 times).
The washed chamber product (0.06% of sulfide sulfur and 2.98% of sulphate sulfur) and foam product (18.1% of sulfide sulfur) were obtained during testing. The results of laboratory studies of the processing of the flotation products are presented.
The flotation and zinc cake washing can reduce zinc cake output by 20-25%, which allows increase of the processing volumes of oxidized imported raw materials by the Waelz-process. Processing of chamber flotation product (zinc cake with low sulfur content) by the Waelz-process can improve the Waelz kiln performance and reduce the coke breeze consumption.
Foam product can be used as a sulfurizing additive under independent processing of copper plant dust with zinc, lead, and tin extraction into fumes.
On the basis of the carried out tests, the project of the processing site of zinc cakes by flotation on the basis of industrial machines CFM-600 and CFM -1400 has been realized.

Natural polymers as products of animal and plant organisms play an irreplaceable role in the life of human society. The main natural polymer raw materials are cellulose, starch, chitin and proteins, which are mainly processed by the food, textile, leather, wood-processing and paper industries. Industrial processing of natural polymers, besides valuable final products, also generates large quantities of by-products, i.e. waste of different composition and quality. Our contribution deals particularly with protein waste (predominantly collagen and keratin) generated by the leather, textile and meat industries. Leather industry is one of major producers of solid protein waste, which often contains also potentially hazardous chemicals. In spite of numerous technological solutions described in the literature for collagen-based wastes, huge amounts of this waste are still left unutilized [1] and its sustainable valorization remains challenging not only from the technological point of view, but also from the viewpoint of commercial application of the products. Common utilization of the products as animal feed or fertilizers may not satisfy the increasing market demand for advanced products, or can be limited due to hygienic regulations related to certain animal by-products; therefore, it is necessary to shift research efforts in protein waste processing towards protein-based products with higher utility value [2] and potential applications in other industries. This also applies to waste keratin (wool, hair, feather...), the unique structure of which makes it difficult to process and to find a feasible and efficient technology of its treatment [3].
We present several successful technological procedures for the processing of protein-based waste generated mainly by the leather, textile and meat industries, from laboratory experiments to scale-up from the laboratory to pilot scale and industrial production using mathematical-physical models verified by laboratory measurements. The procedures specifically include: 1) Processing of potentially hazardous chrome shavings from tanneries; 2) Technology of complete processing of green fleshings, another problematic primary waste from tanneries, into biodiesel and protein hydrolysate; 3) Hybrid technology applied to manipulation waste from footwear production; 4) Processing of protein waste generated during production of collagen casings for the meat industry; 5) Innovative method for the treatment of resistant keratin-based waste from textile and food industries.
The processing technologies are based on hydrolysis of the feedstock carried out in an acidic or alkaline environment. Reactions in an alkaline environment are usually catalyzed by proteolytic enzymes. We also present most recent progress in selected technologies, applications of hydrolysis products in agriculture including eco-farming, and discuss their potential as auxiliary agents in the construction, plastic and rubber industries.