Pyrometallurgical Extraction of Critical Metals for Sustainable Development

A special issue of Processes (ISSN 2227-9717). This special issue belongs to the section "Sustainable Processes".

Deadline for manuscript submissions: closed (31 December 2023) | Viewed by 14354

Special Issue Editors


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Guest Editor
Department of Materials Science and Engineering, University of Toronto, Toronto, ON L5L 1C6, Canada
Interests: sustainable materials; high-quality alloys; waste recycling
Special Issues, Collections and Topics in MDPI journals

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Guest Editor
Mining and Metallurgy, SNC-Lavalin, Toronto, ON M9C 5K1, Canada
Interests: pyrometallurgy; smelting; refining; converting; recycling; technology development

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Guest Editor
Department of Mechanical Engineering, École de Technologie Supérieure, 1100 Notre-Dame St W, Montreal, QC H3C 1K3, Canada
Interests: thermodynamics; high-temperature materials processing; recycling

Special Issue Information

Dear Colleagues,

Critical metals are subject to supply chain risks, but they are simultaneously essential to sustainable development. Key industry sectors and developmental initiatives such as renewable energy transition, advanced manufacturing, aerospace, defense, battery technologies, consumer electronics, electric vehicles, among others, are affected by the supply of critical metals.

Pressure on primary and secondary raw material resources will increase due to the increasing global population, industrialization, digitalization, increasing demand from developing countries, and the transition to climate neutrality. Hence, innovative, optimized, and more efficient extraction process routes and technologies are required to address the global demand.

This Special Issue focuses on the resource identification, pyrometallurgical extraction, separation, and refining of critical metals for sustainable development. Topics include but are not limited to novel/improved processes for the production of:

  • Ferroalloy metals: chromium, cobalt, manganese, nickel, niobium, tantalum, titanium, and vanadium;
  • Precious metals: gold, silver, and platinum group metals (iridium, palladium, platinum, rhodium, and ruthenium);
  • Other non-ferrous metals: aluminum, antimony, bismuth, cadmium, copper, indium, gallium, germanium, lead, lithium, and magnesium.

Prof. Dr. Mansoor Barati
Dr. Sina Mostaghel
Prof. Dr. Elmira Moosavi-Khoonsari
Guest Editors

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Keywords

  • critical metals
  • pyrometallurgy
  • smelting
  • refining
  • converting
  • recycling
  • circular economy

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Published Papers (5 papers)

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Research

18 pages, 9694 KiB  
Article
Development of a Process to Recycle NdFeB Permanent Magnets Based on the CaO-Al2O3-Nd2O3 Slag System
by Ludwig W. Blenau, Daniel Vogt, Oliver Lonski, Abuzar Abrar, Olga Fabrichnaya and Alexandros Charitos
Processes 2023, 11(6), 1783; https://doi.org/10.3390/pr11061783 - 11 Jun 2023
Cited by 2 | Viewed by 2214
Abstract
Nd, Pr and Dy are critical raw materials as major components for rare earth permanent magnets (REPM). These are integral for several components placed for example within electric vehicles and wind turbine generators. REE primary production is mainly realized in China (~80%) and [...] Read more.
Nd, Pr and Dy are critical raw materials as major components for rare earth permanent magnets (REPM). These are integral for several components placed for example within electric vehicles and wind turbine generators. REE primary production is mainly realized in China (~80%) and no REPM recycling industry has been established. Hydrometallurgical recycling routes lead to iron dissolution (66 wt. % Fe in REPM), while pyrometallurgical approaches that utilize SiO2 risk contaminating the produced iron phase. A two-step process is presented that (i) creates an FeOx-CaO-Al2O3-REE2O3 molten slag at 1500 °C through oxidative smelting and (ii) separates an iron-depleted slag phase (CaO-Al2O3-REE2O3) and a molten iron phase via carbothermic or metallothermic reduction at 1700–2000 °C. The slag has been designed as a selective collector phase and the REE2O3 loading within the bulk slag can reach up 25 wt. % REE2O3 at 1700 °C. The contained minerals within the slag exhibit >40 wt. % REE (a higher REE concentration than in the initial REPM). The resulting phases are characterized via ICP-OES, CS and SEM-EDX. In addition, the first results with regard to the downstream hydrometallurgical processing of the CaO-Al2O3-REE2O3 slag are presented aiming at the recovery of REE2O3, as well as of CaO and Al2O3. The latter compounds are to be reused during the first process step, i.e., the oxidative smelting of REPM. Slag leaching with methane sulfonic acid (MSA) and separation with alternative methods, such as solvent extraction, seems promising. Future work will include slag filtration with the aim to separate REE-rich solid phases (minerals) from the slag and also molten salt electrolysis of the produced REE2O3 oxides. Full article
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14 pages, 9699 KiB  
Article
Two Potential Ways of Vanadium Extraction from Thin Film Steelmaking Slags
by Tetiana Shyrokykh, Lukas Neubert, Olena Volkova and Seetharaman Sridhar
Processes 2023, 11(6), 1646; https://doi.org/10.3390/pr11061646 - 28 May 2023
Cited by 3 | Viewed by 1923
Abstract
During the steelmaking process, a great amount of slag is generated as a by-product. Vanadium-bearing steelmaking slags are classified as hazardous and require special handling and storage due to the toxicity of vanadium pentoxides. At the same time, such slags are valuable sources [...] Read more.
During the steelmaking process, a great amount of slag is generated as a by-product. Vanadium-bearing steelmaking slags are classified as hazardous and require special handling and storage due to the toxicity of vanadium pentoxides. At the same time, such slags are valuable sources for the recovery of vanadium. The present work reviews the investigations on vanadium recovery from CaO-SiO2-FeO-V2O5 thin film slags under the neutral and oxidizing conditions in the temperature range 1653 K to 1693 K (1380 °C to 1420 °C) using Single Hot Thermocouple Technique (SHTT). The slag samples were analyzed by SEM/EDX. The results indicated that vanadium pentoxide evaporation can be up to 17.73% under an oxidizing atmosphere, while spinel formation under an argon atmosphere was detected in the conditions of thin film slags. Full article
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19 pages, 4353 KiB  
Article
Assessment of Mass and Energy Balance of Waste Printed Circuit Board Recycling through Hydrogen Reduction in Black Copper Smelting Process
by Aulia Qisthi Mairizal, Agung Yoga Sembada, Kwong Ming Tse, Nawshad Haque and M. Akbar Rhamdhani
Processes 2023, 11(5), 1506; https://doi.org/10.3390/pr11051506 - 15 May 2023
Cited by 1 | Viewed by 2444
Abstract
Due to growing concern over environmental impacts and the pressure to lower carbon footprints in the metals industry, hydrogen (H2) has gained attention as a promising alternative for the replacement of carbon as a reductant and fuel. This paper evaluates the [...] Read more.
Due to growing concern over environmental impacts and the pressure to lower carbon footprints in the metals industry, hydrogen (H2) has gained attention as a promising alternative for the replacement of carbon as a reductant and fuel. This paper evaluates the potential use of hydrogen as an energy source and reducing agent during the processing of waste printed circuit boards (waste PCBs) from e-waste through black copper smelting. The effect of the use of carbon and hydrogen during the reduction–oxidation process was analysed and compared from the perspective of thermodynamics and heat balance. The thermodynamic analyses of waste-PCB processing were carried out using the FactSage thermochemical package for the smelting process at temperatures from 1473 K to 1673 K (1200–1400 °C). The results show that the CO2 emissions can be reduced by 73% when hydrogen is used as the reducing agent. A minimum of 10 wt% of waste PCBs in the feed material can be used to replace the necessary carbon to supply heat for the reduction process. The addition of waste PCBs can increase the volume of slag and affect the composition of the off gas. Full article
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13 pages, 1633 KiB  
Article
Extraction and Recovery of Critical Metals from Electronic Waste Using ISASMELT™ Technology
by Stuart Nicol, Benjamin Hogg, Oscar Mendoza and Stanko Nikolic
Processes 2023, 11(4), 1012; https://doi.org/10.3390/pr11041012 - 27 Mar 2023
Cited by 5 | Viewed by 5065
Abstract
Electronic goods are a major consumer of many critical metals, including copper, nickel, tin, zinc, lead, and precious metals. The processing of end-of-life electronic equipment (E-Scrap) is becoming increasingly important to maintain the supply of the critical metals required globally, and to reduce [...] Read more.
Electronic goods are a major consumer of many critical metals, including copper, nickel, tin, zinc, lead, and precious metals. The processing of end-of-life electronic equipment (E-Scrap) is becoming increasingly important to maintain the supply of the critical metals required globally, and to reduce environmental pollution. Currently, the dominant route for E-Scrap processing is pyrometallurgical processing, with the first stage of processing being reductive smelting to produce a black copper and a ‘clean’ discard slag. The management of the slag in this first step is central to the success of the E-Scrap recycling process. The E-Scrap ISASMELT™ furnace has a highly turbulent bath, providing conditions that generate high rates of zinc fuming and allow a wide range of operable slag conditions. This enables efficient E-Scrap smelting to occur, whilst overcoming the challenges associated with alternative technologies. Operable slag compositions and high zinc fuming are heavily influenced by kinetic processes, with piloting critical to understanding the performance of this process. ISASMELT™ pilot tests were performed, with a wide range of fluxing targets tested to confirm these benefits. The testing demonstrated that high levels of zinc fuming (>80%) are obtained in the E-Scrap ISASMELT™ furnace, decreasing the iron and silica flux additions required to manage the detrimental viscosity effects of zinc in the slag. In addition, it was demonstrated that slags containing high concentrations of alumina (>10 wt%) are operable in an ISASMELT™ furnace. The ISASMELT™ technology was demonstrated to be the only E-Scrap furnace technology able to produce a ‘clean’ discard slag with low concentrations of zinc and minimal fluxing requirements. Full article
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25 pages, 5023 KiB  
Article
Development of Experimental Techniques for the Phase Equilibrium Study in the Pb-Fe-O-S-Si System Involving Gas, Slag, Matte, Lead Metal and Tridymite Phases
by Taufiq Hidayat, Ata Fallah-Mehrjardi, Maksym Shevchenko, Peter C. Hayes and Evgueni Jak
Processes 2023, 11(2), 372; https://doi.org/10.3390/pr11020372 - 25 Jan 2023
Cited by 2 | Viewed by 1792
Abstract
Present society challenges, including metal scarcity, recycling, and environmental restrictions, resulted in the increased complexity and variability of metallurgical feed streams. Metallurgical processes involving complex lead and copper-containing slag and matte phases are now commonly used in response. Optimization of existing and development [...] Read more.
Present society challenges, including metal scarcity, recycling, and environmental restrictions, resulted in the increased complexity and variability of metallurgical feed streams. Metallurgical processes involving complex lead and copper-containing slag and matte phases are now commonly used in response. Optimization of existing and development of new metallurgical processes require fundamental information on slag–matte phase equilibrium. Development of the experimental methodology for the characterization of slag–matte phase equilibrium is presented in the paper. Following a detailed analysis of the potential reaction pathways, experimental techniques have been developed that enable accurate measurement of slag–matte phase equilibrium in the Pb-Fe-O-S-Si system. The application of the techniques has been demonstrated for two important sets of conditions: (i) Condensed phase equilibrium for the slag–matte–metal–tridymite subsystem; and (ii) Gas–slag–matte–tridymite equilibrium at fixed oxygen and sulfur partial pressures. The experimental methodology involves high-temperature equilibration of synthetic samples, fast quenching, and microanalysis of the compositions of phases using electron probe X-ray microanalysis (EPMA). The experimental results are not affected by the changes in the bulk composition of samples during equilibration; this helps to overcome the significant barriers previously encountered in undertaking accurate measurement and characterization of these systems. Full article
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