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Feature Papers in Extractive Metallurgy
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Feature Papers in Extractive Metallurgy

A special issue of Metals (ISSN 2075-4701). This special issue belongs to the section "Extractive Metallurgy".

Deadline for manuscript submissions: 10 April 2025 | Viewed by 9684

Special Issue Editor

Dr. Srecko Stopic

E-Mail Website
Guest Editor
IME Process Metallurgy and Metal Recycling Department, RWTH Aachen University, 52056 Aachen, Germany
Interests: waste water treatment; synthesis of metallic; oxidic and composite nanopowder; recycling of dust and FeZn-concentrates; environment protection; unit operations in non-ferrous metallurgy; hydrometallurgy and rare earth elements; hydrogen reduction; titanium and aluminium residues
Special Issues, Collections and Topics in MDPI journals

Special Issue Information

Dear Colleagues,

Extractive metallurgy deals with the processes for the recovery of valuable metals from ores and concentrates (primary metallurgy) or waste raw materials such as slags, slime and flying ashes (recycling or secondary metallurgy). Regarding the type of obtained metals, these processes are divided in five different groups: extractive metallurgy of iron and steel, non-ferrous extractive metallurgy, extractive metallurgy of precious metals, extractive metallurgy of rare earth elements and refractory metal extractive metallurgy. These processes in extractive metallurgy include unit processes for separating highly pure metals from undesirable metals in an economically efficient system. Decarbonated processes will be considered using green hydrogen in order to promote extractive metallurgy aimed towards an environmental protection and zero-waste concept.

Unit metallurgical operation processes are usually separated into three categories: 1) hydrometallurgy (leaching, mixing, neutralization, precipitation, cementation, crystallization), 2) pyrometallurgy (roasting, smelting), and 3) electrometallurgy (aqueous electrolysis and molten salt electrolysis). In hydrometallurgy, the target metal is first transferred from ores and concentrates to a solution using selective dissolution (leaching; dry digestion) under an atmospheric pressure below 100 °C and under a high pressure (40-50 bar) and high temperature (below 270°C) in an autoclave and tube reactor. The purification of the obtained solution was performed using neutralization agents such as sodium hydroxide and calcium carbonate or more selective precipitation agents such as sodium carbonate and oxalic acid. The separation of metals is possible using liquids/liquid processes (solvent extraction in a mixer-settler) and solid–liquid (filtration in filter-press under high pressure) methods. Crystallization is the process by which a metallic compound is converted from a liquid into a solid crystalline state via a supersaturated solution. The final step is metal production using electrochemical methods (aqueous electrolysis for basic metals such as copper, zinc, silver and molten salt electrolysis for rare earth elements and aluminium). Advanced processes for metal production, such as ultrasonic spray pyrolysis and microwave-assisted leaching, can be combined with reduction processes.

Some preparation for the leaching process is performed via a roasting process in a rotary furnace, where the sulfidic ore was first oxidized in an oxidic form, which is suitable for the metal transfer to water solution. During the smelting process, the target metal is further refined at high temperatures and reduced to its pure form. The pyrometallurgical treatment of the ore was performed in an electric furnace and combined with refining during distillationCircular hydrometallurgy can be involved in this consideration, enabling the design of energy-efficient and resource-efficient flowsheets or unit processes that consume the minimum quantities of reagents and result in minimum waste. Treatment of waste water from metallurgical processes is an important subject considering the consumption of water and energy must also be reduced to an absolute minimum. 

Since metals are manly existent in the solid and liquid state, analysis of the processes involved focuses on solid–liquid, liquid–liquid, liquid–gas, solid–solid, solid–liquid–gas, and solid–gas reactions. The theory of metallurgical processes will be deeply involved in this consideration determining reaction mechanisms (reaction models) on which kinetic models are based. Designing an industrial process requires a kinetic model in the first place. Kinetic models describe at which rate a reaction is happening (reaction and reverse reaction). If or under which conditions a reaction happens is part of thermochemical calculation. Computational thermochemistry can assist in the prediction of different chemical reactions and material selection in these extreme operation conditions to select refractory materials in contact with metallic melts and high corrosive media. The FactSage thermochemical software and its specialized databases can be used to perform these simulations that are proven here to match the available data found in the literature. The OLI, HSC and other software can be used to perform these simulations for hydrometallurgical processes in order to enable the selective winning of metals from solution.

Dr. Srecko Stopic
Guest Editor

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Keywords

  • extractive metallurgy
  • unit operations
  • hydrometallurgy
  • pyrometallurgy
  • electrometallurgy
  • precious metals
  • refractory metals
  • rare earth elements
  • kinetics
  • thermochemistry
  • simulation
  • iron and steel
  • modelling
  • environmental protection
  • hydrogen
  • decarbonation
  • kinetics
  • reduction
  • oxidation

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Published Papers (6 papers)

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Research

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21 pages, 13790 KiB  
Article
Characterisation of Varying Iron Ores and Their Thermal Decomposition Kinetics Under HIsarna Ironmaking Conditions
by Philipp Leerhoff, Johannes C. Brouwer, Amir Mohseni Armaki, Christiaan Zeilstra, Koen Meijer, Jan van der Stel, Shoshan T. Abrahami, Neslihan Dogan and Yongxiang Yang
Metals 2024, 14(11), 1271; https://doi.org/10.3390/met14111271 - 8 Nov 2024
Viewed by 662
Abstract
In the pre-reduction cyclone of the HIsarna process, both thermal decomposition and gas reduction of the injected iron ores occur simultaneously at gas temperatures of 1723–1773 K. In this study, the kinetics of the thermal decomposition of three iron ores (namely OreA, OreB [...] Read more.
In the pre-reduction cyclone of the HIsarna process, both thermal decomposition and gas reduction of the injected iron ores occur simultaneously at gas temperatures of 1723–1773 K. In this study, the kinetics of the thermal decomposition of three iron ores (namely OreA, OreB and OreC) for HIsarna ironmaking were analysed as an isolated process with a symmetrical thermogravimetric analyser (TGA) under an inert atmosphere. Using various methods, the chemical and mineralogical composition, particle size distribution, morphology and phase distribution of the ores were analysed. The ores differ in their mineralogy and morphology, where OreA only contains hematite as iron-bearing phase and OreB and OreC include goethite and hematite. To obtain the kinetic parameters in non-isothermal conditions, the Coats–Redfern Integral Method was applied for heating rates of 1, 2 and 5 K/min and a maximum temperature of 1773 K. The TGA results indicate that goethite and hematite decomposition occur as a two-stage process in an inert atmosphere of Ar. The proposed reaction mechanism for the first stage of goethite decomposition is chemical reaction with an activation energy ranging from 46.55 to 60.38 kJ/mol for OreB and from 69.90 to 134.47 kJ/mol for OreC. The proposed reaction mechanism for the second stage of goethite decomposition is diffusion, showing an activation energy ranging between 24.43 and 44.76 kJ/mol for OreB and between 3.32 and 23.29 kJ/mol for OreC. In terms of hematite decomposition, only the first stage was analysed. The proposed reaction mechanism is chemical reaction control. OreA shows an activation energy of 545.47 to 670.50 kJ/mol, OreB one of 587.68 to 831.54 kJ/mol and OreC one of 424.31 to 592.32 kJ/mol. Full article
(This article belongs to the Special Issue Feature Papers in Extractive Metallurgy)
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17 pages, 5401 KiB  
Article
Mineralogical Characterisation of Copper Slag and Phase Transformation after Carbocatalytic Reduction for Hydrometallurgical Extraction of Copper and Cobalt
by Tina Chanda Phiri, Pritam Singh and Aleksandar N. Nikoloski
Metals 2024, 14(10), 1119; https://doi.org/10.3390/met14101119 - 1 Oct 2024
Viewed by 748
Abstract
Copper smelting slag is a significant potential resource for cobalt and copper. The recovery of copper and cobalt from copper slag could significantly augment the supply of these metals, which are essential to facilitating the transition to green energy while simultaneously addressing environmental [...] Read more.
Copper smelting slag is a significant potential resource for cobalt and copper. The recovery of copper and cobalt from copper slag could significantly augment the supply of these metals, which are essential to facilitating the transition to green energy while simultaneously addressing environmental concerns regarding slag disposal. However, the complex mineral composition of copper slag poses an enormous challenge. This study investigated the mineralogical and chemical characteristics of copper slag, which are vital for devising the most effective processing techniques. XRD and FESEM-EDS were employed to examine the morphologies of copper slag before and after the reduction process. The effects of borax and charcoal (carbocatalytic) reduction on phase transformation were evaluated. The XRD analysis revealed that the primary phases in the copper slag were Fe2SiO4 and Fe3O4. The FESEM-EDS analysis verified the presence of these phases and yielded supplementary details regarding metal embedment in the Fe2SiO4, Fe3O4, and Cu phases. The carbocatalytic reduction process expedited the transformation of copper slag microstructures from crystalline dendritic to amorphous and metallic phases. Finally, leaching experiments demonstrated the potential benefits of carbocatalytic reduction by yielding high extractions of Cu, Co, and Fe. Full article
(This article belongs to the Special Issue Feature Papers in Extractive Metallurgy)
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13 pages, 3441 KiB  
Article
Electrochemical Behaviour of an Au-Ge Alloy in an Artificial Saliva and Sweat Solution
by Gyöngyi Vastag, Peter Majerič, Vojkan Lazić and Rebeka Rudolf
Metals 2024, 14(6), 668; https://doi.org/10.3390/met14060668 - 5 Jun 2024
Viewed by 784
Abstract
In modern times, more and more different materials (including alloys) are in direct contact with human electrolytes (sweat, saliva, lymph, blood, etc.). One of the most important properties for the use of these materials is therefore their chemical inertness or resistance to corrosion [...] Read more.
In modern times, more and more different materials (including alloys) are in direct contact with human electrolytes (sweat, saliva, lymph, blood, etc.). One of the most important properties for the use of these materials is therefore their chemical inertness or resistance to corrosion when they are in contact with human electrolytes. Consequently, during the development of such new materials, it is necessary to study and understand their basic electrochemical behaviour in a given environment. The purpose of this research was to monitor the electrochemical behaviour of the new Au-Ge alloy in artificial sweat and artificial saliva solutions, depending on the electrolyte composition and exposure time. This new alloy represents a potential material for use in dentistry or for jewellery. The obtained results of the study show that the immersion time and the pH value have a significantly greater influence on the corrosion resistance of the new Au-Ge alloy than the composition of the electrolyte solution. The results of the SEM/EDX analysis additionally confirm the main results of the electrochemical measurements. Full article
(This article belongs to the Special Issue Feature Papers in Extractive Metallurgy)
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18 pages, 2358 KiB  
Article
Importance of Changes in the Copper Production Process through Mining and Metallurgical Activities on the Surface Water Quality in the Bor Area, Serbia
by Radmila Marković, Vesna M. Marjanović, Zoran Stevanović, Vojka Gardić, Jelena Petrović, Renata Kovačević, Zoran Štirbanović and Bernd Friedrich
Metals 2024, 14(6), 649; https://doi.org/10.3390/met14060649 - 29 May 2024
Viewed by 961
Abstract
This paper considers the impact of copper mining-influenced water and metallurgical wastewater on the surface water in the Bor area, Serbia. Sampling, realized through the four campaigns (2020–2021), confirmed that both types of water, discharged without appropriate treatment in the Bor River, had [...] Read more.
This paper considers the impact of copper mining-influenced water and metallurgical wastewater on the surface water in the Bor area, Serbia. Sampling, realized through the four campaigns (2020–2021), confirmed that both types of water, discharged without appropriate treatment in the Bor River, had a signific impact on the concentration of metal ions, pH and electrical conductivity on the watercourse in the Bor area. The highest concentrations of the following metal ions, Cu—271 mg/L, As—25,991 μg/L, Ni—13,856 μg/L, Cd—2627 μg/L, and Pb—2855 μg/L, were registered in the metallurgical wastewater samples. After changes occurred in the copper production process by stopping the discharge of untreated wastewater into the Bor River, the concentrations of monitored elements were drastically decreased. In the period 2022–2024, the concentration values for Cu, As and Pb ions were below the maximum allowable value, and the concentration values of Ni and Cd ions were also decreased. The values for pH and electrical conductivity were in the maximum allowable range. The return of wastewater to the copper production process would lead to both a reduction in the primary water consumption and reduction in the negative impact on the environment. Full article
(This article belongs to the Special Issue Feature Papers in Extractive Metallurgy)
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12 pages, 23907 KiB  
Article
From Bauxite as a Critical Material to the Required Properties of Cast Aluminum Alloys for Use in Electro Automotive Parts
by Mile Djurdjevic, Srecko Manasijevic, Marija Mihailović and Srecko Stopic
Metals 2023, 13(11), 1796; https://doi.org/10.3390/met13111796 - 25 Oct 2023
Cited by 6 | Viewed by 2198
Abstract
There is a long process to transform bauxite, a critical raw material, into a substance with the required properties of cast aluminum alloys for use in electro automotive parts. Thanks to its unique properties, aluminum has become the material of choice for clean [...] Read more.
There is a long process to transform bauxite, a critical raw material, into a substance with the required properties of cast aluminum alloys for use in electro automotive parts. Thanks to its unique properties, aluminum has become the material of choice for clean technology manufacturers in applications such as use in the automotive industry, renewable energy, batteries, electrical systems, resource-saving packaging, energy efficient buildings and clean mobility. Restructuring of the economy, the oil crisis, air pollution and global warming are some of the factors that have moved the automotive industry towards electrification since the beginning of the 21st century. This paper aims to highlight the required properties of cast aluminum alloys applied to the production of electro automotive parts, such as their mechanical and thermophysical properties, dimensional stability, corrosion resistance, electromagnetic compatibility and crashworthiness. Furthermore, this paper discusses which of the cast aluminum–silicon alloys, as well as the heat treatments and casting processes, are most suitable. Full article
(This article belongs to the Special Issue Feature Papers in Extractive Metallurgy)
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Review

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15 pages, 7097 KiB  
Review
Recent Status of Production, Administration Policies, and Low-Carbon Technology Development of China’s Steel Industry
by Yufeng Qiao and Guang Wang
Metals 2024, 14(4), 480; https://doi.org/10.3390/met14040480 - 20 Apr 2024
Cited by 9 | Viewed by 3282
Abstract
In 2023, China’s crude steel production amount reached 1.019 billion tons, and the energy consumption of China’s steel industry amount reached 561 million tons of coal. China’s steel industry, with its dominant reliance on coal for energy and the primary use of blast [...] Read more.
In 2023, China’s crude steel production amount reached 1.019 billion tons, and the energy consumption of China’s steel industry amount reached 561 million tons of coal. China’s steel industry, with its dominant reliance on coal for energy and the primary use of blast furnaces and converters in production processes, as well as its massive output, has become the main field for achieving China’s “carbon peaking” and “carbon neutrality” goals. Firstly, this article summarizes the current production status of the steel industry and the situation of carbon emissions in the steel industry. Secondly, it discusses the dual-carbon policies based on the national and steel industry levels and outlines the future directions for China’s steel industry. Subsequently, it analyzes the current state of research and application of mature and emerging low-carbon technology in China’s steel industry and details the low-carbon plans of China’s steel companies using the low-carbon technology roadmaps of two representative steel companies as examples. Finally, the article gives policy suggestions for the further carbon reduction of China’s steel industry. The purpose of this paper is to show the efforts and contributions of China’s steel industry to the early realization of its “carbon peaking” and “carbon neutrality” goals. Full article
(This article belongs to the Special Issue Feature Papers in Extractive Metallurgy)
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