Waste Valorization: Recycling and Recovery of Critical and Strategic Metals

A special issue of Minerals (ISSN 2075-163X). This special issue belongs to the section "Mineral Processing and Extractive Metallurgy".

Deadline for manuscript submissions: 30 June 2025 | Viewed by 2527

Special Issue Editors


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Guest Editor
Department of Materials Science and Engineering, Norwegian University of Science and Technology, 7034 Trondheim, Norway
Interests: hydrometallurgy; pyrometallurgy; recycling of critical metals from secondary sources; recycling of permanent magnets and solar cell

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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
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Guest Editor
IFE, Institute for Energy Technology, Instituttveien 18, 2007 Oslo, Norway
Interests: pyrometallurgy; hydrometallurgy; leaching; precipitation; neutralization; redox reactions; metal extraction/recovery; recycling; deep eutectic solvents; tailings utilization; tailings minimization and utilization; rare earth chemistry; oxygen carriers; CO2 mineralization

Special Issue Information

Dear Colleagues,

This Special Issue focuses on innovative approaches and methodologies for valorizing waste including mineral waste and end-of-life (EoL) products through the recycling and recovery of critical and strategic metals, including, but not limited to, rare earth elements, cobalt, copper, nickel, lithium, silver, aluminum, titanium, and silicon. Given the growing demand for these metals in high-tech and green energy industries, sustainable waste management practices are imperative.

Key topics include, but are not limited to, the following:

  • Extraction and Purification processes:  Hydrometallurgical techniques for recovering critical and strategic metals from industrial by-products, mineral residues, and EoL products.
  • Recycling Technologies: Cutting-edge approaches to enhance the efficiency and cost-effectiveness of recycling critical and strategic metals from waste streams such as sludge, redmud, tailings, slag, and EoL products, utilizing pyrometallurgical, hydrometallurgical, and electrometallurgical methods.
  • Thermodynamical Modeling and Process Simulation: In-depth studies on the thermodynamical aspects of metal extraction processes, including modeling and simulation techniques, to optimize and tailoring the recycling techniques.
  • Economic and Environmental benefits: Comprehensive assessments of the potential economic gains and environmental impacts of critical/strategic metal recovery, fostering a circular economy and sustainability.
  • Case studies: Practical applications in the valorization of mineral waste and the extraction of critical and strategic raw materials.

This Issue aims to provide a thorough understanding of the challenges and opportunities in transforming waste into valuable resources, thereby promoting sustainable development and reducing the ecological footprint of mining and industrial activities.

Dr. Elif Emil Kaya
Dr. Srecko Stopic
Dr. Duygu Yilmaz
Guest Editors

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Keywords

  • recycling and utilization of waste and industrial by-product
  • extraction of critical and strategic metals from mineral waste, EoL products, and industrial by-products
  • hydrometallurgy
  • pyrometallurgy
  • electrometallurgy
  • leaching, precipitation, solvent extraction
  • melting, hydrogen/metallothermic reduction
  • thermodynamical modeling and process simulations

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Published Papers (2 papers)

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Research

14 pages, 3032 KiB  
Article
Recovery of Titanium from Red Mud Using Carbothermic Reduction and High Pressure Leaching of the Slag in an Autoclave
by Srecko Stopic, Duško Kostić, Richard Schneider, Magnus Sievers, Florian Wegmann, Elif Emil Kaya, Mitar Perušić and Bernd Friedrich
Minerals 2024, 14(11), 1151; https://doi.org/10.3390/min14111151 - 13 Nov 2024
Viewed by 628
Abstract
Red mud is a by-product of alumina production, which is largely stored in landfills that can endanger the environment. Red mud, or bauxite residue, is a mixture of inorganic compounds of iron, aluminum, sodium, titanium, calcium and silicon mostly, as well as a [...] Read more.
Red mud is a by-product of alumina production, which is largely stored in landfills that can endanger the environment. Red mud, or bauxite residue, is a mixture of inorganic compounds of iron, aluminum, sodium, titanium, calcium and silicon mostly, as well as a large number of rare earth elements in small quantities. Although certain methods of using red mud already exist, none of them have been widely implemented on a large scale. This paper proposes a combination of two methods for the utilization of red mud, first by carbothermic reduction and then, by leaching under high pressure in an autoclave in order to extract useful components from it with a focus on titanium. In the first part of the work, the red mud was reduced with carbon at 1600 °C in an electric arc furnace, with the aim of removing as much iron as possible using magnetic separation. After separation, the slag is leached in an autoclave at different parameters in order to obtain the highest possible yield of titanium, aiming for the formation of titanium oxysulfate and avoiding silica gel formation. A maximal leaching efficiency of titanium of 95% was reached at 150 °C using 5 mol/L sulfuric acid with 9 bar oxygen in 2 h. We found that high-pressure conditions enabled avoiding the formation of silica gel during leaching of the slag using 5 mol/L sulfuric acid, which is a big problem at atmospheric pressure. Previously silica gel formation was prevented using the dry digestion process with 12 mol/L sulfuric acid under atmospheric pressure. Full article
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11 pages, 4979 KiB  
Article
Effects of Size and Mechanical Pre-Treatment on Aluminium Recovery from Municipal Solid Waste Incineration Bottom Ash
by Mertol Gökelma, Utku Hatipoğlu, Alicia Vallejo-Olivares, Rabia Önen Tüzgel, Olcay Kıvrak, Elif Bazoğlu, Zeynep Su Çizen and Gabriella Tranell
Minerals 2024, 14(10), 1006; https://doi.org/10.3390/min14101006 - 5 Oct 2024
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Abstract
Municipal solid waste (MSW) is incinerated to reduce the volume and recover energy and materials. The generation of MSW has been increasing over the past few decades due to the increase in population and changing consumption habits. Rising environmental and economic concerns have [...] Read more.
Municipal solid waste (MSW) is incinerated to reduce the volume and recover energy and materials. The generation of MSW has been increasing over the past few decades due to the increase in population and changing consumption habits. Rising environmental and economic concerns have increased the importance of waste treatment and recovery. Currently, MSW may take three alternate or parallel routes: direct recycling, incineration, or landfill, depending on the country and location. MSW incineration has three products in addition to energy: bottom ash, fly ash, and off-gas. After incineration, bottom ash usually still contains many materials to be recovered, such as glass, ceramics, and metals with a degree of oxidation. This study focuses on aluminium recovery from MSW incineration bottom ash from two different countries. The 2–30 mm fraction of aluminium particles was characterized in terms of its size, shape, and oxide thickness, and its effects on aluminium recovery were investigated. In addition, the ability of mechanical pre-treatment to remove oxides prior to melting was studied. The results were compared with the analytical modeling developed in this study. An increasing particle size and surface area resulted in an increase in aluminium recovery. Mechanical pre-treatment increased the yield for smaller particles to a larger extent than larger particles due to the difference in the oxide/metal ratio. Full article
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