Artificial Engineered Minerals: Synthesis, Characterization, Metallurgical and Mechanical Processing

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

Deadline for manuscript submissions: 31 October 2024 | Viewed by 2838

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Institute of Mechanical Process Engineering and Mineral Processing, TU Bergakademie Freiberg, 09599 Freiberg, Germany
Interests: mechanical separation processes; solid liquid separation; recycling and mineral processing; particle-particle interactions; particle characterization
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Institute of Inorganic and Analytical Chemistry, TU Clausthal, 38678 Clausthal-Zellerfeld, Germany
Interests: elemental and element species determination; materials analysis; phase separation

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Guest Editor
The Fraunhofer Research Group, TH Nürnberg, Wassertorstraße 10, 90489 Nürnberg, Germany
Interests: comminution and separation processes; mechanochemical reactions and co-cristallisation; fine powder handling

Special Issue Information

Dear Colleagues,

We are led to believe in the high and sustainable recycling rates of consumer products; however, the recycling industry primarily focuses on recovering the main bulk materials. This oversight results in the under-recognition and loss of metals essential for advanced technological functions in waste streams, such as Ta and Li incorporated into building materials, Nd and Dy dissolved in iron-based construction materials, and Pd dispersed as dust across various process streams. Consequently, this leads to downcycling and the depletion of valuable chemical species. To address this issue, the future circular economy (CE) must develop processing technologies that maximize the recovery of all 60 different elements utilized in our technical society’s products.

The ongoing developments in materials and the increased functionality of technical products, exemplified by the complexity of materials in e-mobility, necessitate the tracing of all relevant chemical elements through mechanical and metallurgical recycling processes. This tracking enables closing of material streams and identifies the whereabouts of each element within the cycle. A novel technological concept, Engineered Artificial Minerals (EnAM), allows for the selective concentration and retrieval of specific elements from small-scale components and multi-material composites. The EnAM concept involves tailored development and application of thermodynamic and crystallization research to generate EnAM-crystals during pyrometallurgical processing, and it furthermore evaluates the mechanical steps for downstream processing. Thus, the concentration of a target species involves a two-stage process: first, during the pyrometallurgical treatment, the target element is integrated into a specific artificial mineral phase, representing in most cases only a small fraction of the entire slag; second, the liberation and separation of this artificial mineral as particles from the overall slag stream. The key methods for understanding and quantifying these processes, as well as tracing individual elements, include in situ monitoring of the formation processes and multidimensional analysis of the solid EnAM structure/texture at each process stage.

In terms of a holistic picture, we have to apply an integrated model and simulation approach, as well as develop and utilize new process models leading to digital twins of the related processes. This also necessitates the development of an enhanced entropy concept to quantitatively describe the mixture and inner structure of the material flows. This approach integrates both the particle and thermochemical processes of metallurgy into a single digital tool. It serves as a method to estimate the recycling effort for each chemical element in each material, coupling to economic, ecological, and life-cycle assessment models to allow for predictive simulations to determine the most efficient and feasible recycling concept for each element or feed stream.

Prof. Dr. Urs Alexander Peuker
Prof. Dr. Bernd Friedrich
Prof. Dr. Ursula Elisabeth Adriane Fittschen
Prof. Dr. Sandra Breitung-Faes
Guest Editors

Manuscript Submission Information

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Keywords

  • metallurgical recycling
  • pyrometallurgy
  • mineral processing
  • grain size distribution
  • crushing, milling, breakage and liberation
  • mechanical sorting
  • flotation, magnetic separation, density separation, electrostatic separation
  • flow sheet simulation
  • DEM-modelling and simulation
  • thermodynamic modelling and simulation
  • phase equilibrium and crystallization
  • metallurgical slags
  • Controlled Solidification
  • e-waste and spent batteries

Published Papers (3 papers)

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Research

15 pages, 4931 KiB  
Article
Stabilization of Mn4+ in Synthetic Slags and Identification of Important Slag Forming Phases
by Alena Schnickmann, Danilo Alencar De Abreu, Olga Fabrichnaya and Thomas Schirmer
Minerals 2024, 14(4), 368; https://doi.org/10.3390/min14040368 - 30 Mar 2024
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Abstract
The expected shortage of Li due to the strong increase in electromobility is an important issue for the recovery of Li from spent Li-ion batteries. One approach is pyrometallurgical processing, during which ignoble elements such as Li, Al and Mn enter the slag [...] Read more.
The expected shortage of Li due to the strong increase in electromobility is an important issue for the recovery of Li from spent Li-ion batteries. One approach is pyrometallurgical processing, during which ignoble elements such as Li, Al and Mn enter the slag system. The engineered artificial mineral (EnAM) strategy aims to efficiently recover critical elements. This study focuses on stabilizing Li-manganates in a synthetic slag and investigates the relationship between Mn4+ and Mg and Al in relation to phase formation. Therefore, three synthetic slags (Li, Mg, Al, Si, Ca, Mn, O) were synthesized. In addition to LiMn3+O2, Li2Mn4+O3 was also stabilized. Both phases crystallized in a Ca-silicate-rich matrix. In the structures of Li2MnO3 and LiMnO2, Li and Mn can substitute each other in certain proportions. As long as a mix of Mn2+ and Mn3+ is present in the slag, spinels form through the addition of Mg and/or Al. Full article
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36 pages, 5708 KiB  
Article
Behavior of Tantalum in a Fe-Dominated Synthetic Fayalitic Slag System—Phase Analysis and Incorporation
by Thomas Schirmer, Jessica Hiller, Joao Weiss, Daniel Munchen, Hugo Lucas, Ursula E. A. Fittschen and Bernd Friedrich
Minerals 2024, 14(3), 262; https://doi.org/10.3390/min14030262 - 29 Feb 2024
Viewed by 867
Abstract
Pyrometallurgical processes produce slags that may contain valuable elements because of their high oxygen affinity. However, the concentration is extremely low, which causes losses. In fact, these elements, for example, tantalum and rare earth elements, are less than 1% recycled. To return such [...] Read more.
Pyrometallurgical processes produce slags that may contain valuable elements because of their high oxygen affinity. However, the concentration is extremely low, which causes losses. In fact, these elements, for example, tantalum and rare earth elements, are less than 1% recycled. To return such technologically important elements to the material cycle, pyrometallurgically is used to enrich them in the simplest possible compounds within the slag, which have favorable properties for recovery (morphology, crystal size, magnetic properties), allowing further mechanical separation. The purpose of modification of the slag system is to obtain engineered artificial minerals” (EnAM), a process in which targeted minerals with high element concentration are formed. In this article, this approach is investigated using tantalum-rich fayalitic slag, since this slag is commonly found in the industry for the pyrometallurgical treatment of waste electric and electronic equipment. Synthetic fayalitic slags in reducing environment under different cooling rates were produced with Ta addition. The characterization of the produced samples was carried out using powder X-ray diffraction (PXRD) and electron probe microanalysis (EPMA). Additionally, the speciation of Fe and Ta was accessible through X-ray absorption near-edge structure (XANES) spectroscopy. EPMA also provided a semiquantitative assessment of the Ta distribution in these individual compounds. In these slags, tantalum accumulated in perovskite-like oxidic and silicate compounds as well as in magnetic iron oxides. The enrichment factor is highest in tantalite/perovskite-type oxides (FexTayO6, CaxFeyTazO3) with up to 60 wt.% Ta and ‘tantalomagnetite’ (FeII(FeIII(2-5/3x)Tax)O4) with a maximum of ~30 wt.% Ta (only fast cooling). This is followed by a perovskite-like silicon containing oxide (XYO3) with 12–15 wt.% Ta (only slow cooling), and a hedenbergite-like compound (XYZ2O6) with a varying content of 0.3–7 wt.%. The Ta concentration in pure Fe, Fe(1-x)O, hercynitic spinel and hematite is negligible. Despite the very low phase fraction, the most promising EnAM compound is nevertheless perovskite-like tantalum oxide, as the highest enrichment factor was obtained. Tantalum-rich magnetite-like oxides also could be promising. Full article
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18 pages, 8984 KiB  
Article
Characterisation of the Grain Morphology of Artificial Minerals (EnAMs) in Lithium Slags by Correlating Multi-Dimensional 2D and 3D Methods
by Cindytami Rachmawati, Joao Weiss, Hugo Ignacio Lucas, Erik Löwer, Thomas Leißner, Doreen Ebert, Robert Möckel, Bernd Friedrich and Urs Alexander Peuker
Minerals 2024, 14(2), 130; https://doi.org/10.3390/min14020130 - 25 Jan 2024
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Abstract
Slags from the metallurgical recycling process are an important source of resources classified as critical elements by the EU. One example is lithium from Li-ion battery recycling. In this context, the thermodynamic properties of the recycled component system play a significant role in [...] Read more.
Slags from the metallurgical recycling process are an important source of resources classified as critical elements by the EU. One example is lithium from Li-ion battery recycling. In this context, the thermodynamic properties of the recycled component system play a significant role in the formation of the Li-bearing phases in the slag, in this case, LiAlO2. LiAlO2 crystal formation could be engineered and result in varying sizes and occurrences by different metallurgical processing conditions. This study uses pure ingredients to provide a synthetic model material which can be used to generate the valuable phase in the slag, or so-called engineered artificial minerals (EnAMs). The aim is to investigate the crystallisation of LiAlO2 as an EnAM by controlling the cooling conditions of the model slag to optimise the EnAM formed during crystallisation. Characterisation of the EnAMs is an important step before further mechanically processing the material to recover the valuable element Li, the Li-bearing species, respectively. Investigations are conducted using powder X-ray diffraction (XRD), X-ray fluorescence (µXRF), and X-ray Computer Tomography (XCT) on two different artificial lithium slags from MnO-Al2O3-SiO2-CaO systems with different cooling temperature gradients. The result shows the different EnAM morphology along the height of the slag, which is formed under different slag production conditions in a semi-pilot scale experiment of 5 kg. Based on the different EnAM morphologies, three defined qualities of the EnAM are identified: granular, dendritic, and irregular-shape EnAM. Full article
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