Special Issue "Valorization of Metallurgical and Mining Residues and Wastes"

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

Deadline for manuscript submissions: closed (15 November 2021) | Viewed by 15712

Special Issue Editors

Prof. Dr. George Angelopoulos
E-Mail Website
Guest Editor
Laboratory of Materials and Metallurgy, Department of Chemical Engineering, University of Patras, Caratheodori 1, 26504 Patras, Greece
Interests: high-temperature processes; industrial symbiosis; circular economy; valorization of secondary raw materials and of inorganic residues/wastes
Prof. Dr. Luis Pérez Villarejo
E-Mail Website
Guest Editor
Department of Chemical, Environmental, and Materials Engineering, University of Jaen, 23700 Linares, Spain
Interests: byproduct and industrial residue valorization; ceramics; cements; alkali-activated materials; synthesis of nanomaterials
Special Issues, Collections and Topics in MDPI journals

Special Issue Information

Dear Colleagues,

The objective of this Special Issue is to offer an updated and profound view of recent advances in the reuse of mining and metallurgical secondary materials/byproducts/wastes, as well as to offer a complete view of the improvements in the processes involved, such as new process routes and chemical routes that concern the recovery of strategic materials, i.e., rare earth metals and manufacture of new materials that can lead to a greener environmental footprint.

Mining and metallurgical activities generate high volumes of secondary materials, in other words, byproducts such as slags, mining wastes, sludges, dusts, ore processing tailings, and leaching residues, which in several cases are damped or released “as they are” or after post-treatment to the environment. Many of them can be used after proper processing as potential raw materials. Moreover, in several cases, for their creation, consumption of major natural resources is required. Therefore, they are associated with a significant environmental footprint. Mining and metallurgical secondary material/byproducts/wastes should not be disposed of but utilized or if possible valorized both from an economic and environmental point of view. Recycling/utilization is an essential aspect of the circular economy in order “to close the loop”.

Prof. Dr. Luis Pérez Villarejo
Prof. Dr. George Angelopoulos
Guest Editors

Manuscript Submission Information

Manuscripts should be submitted online at www.mdpi.com by registering and logging in to this website. Once you are registered, click here to go to the submission form. Manuscripts can be submitted until the deadline. All submissions that pass pre-check are peer-reviewed. Accepted papers will be published continuously in the journal (as soon as accepted) and will be listed together on the special issue website. Research articles, review articles as well as short communications are invited. For planned papers, a title and short abstract (about 100 words) can be sent to the Editorial Office for announcement on this website.

Submitted manuscripts should not have been published previously, nor be under consideration for publication elsewhere (except conference proceedings papers). All manuscripts are thoroughly refereed through a single-blind peer-review process. A guide for authors and other relevant information for submission of manuscripts is available on the Instructions for Authors page. Minerals is an international peer-reviewed open access monthly journal published by MDPI.

Please visit the Instructions for Authors page before submitting a manuscript. The Article Processing Charge (APC) for publication in this open access journal is 2000 CHF (Swiss Francs). Submitted papers should be well formatted and use good English. Authors may use MDPI's English editing service prior to publication or during author revisions.

Keywords

  • Environmental footprint
  • Green processes
  • Circular economy
  • Energy efficiency
  • Energy recovery
  • Secondary materials/byproducts/wastes
  • New products
  • Metallurgical wastes
  • Valorization
  • Mining residues
  • Value recovery
  • Leachate
  • Metal recovery
  • Raw materials
  • Waste processing
  • Waste management

Published Papers (14 papers)

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Research

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Article
A Contribution towards a More Sustainable Cement: Synergy of Mill Scales, Greek Wet Fly Ash, Conventional Raw Materials and Clinkering Temperature
Minerals 2022, 12(3), 324; https://doi.org/10.3390/min12030324 - 05 Mar 2022
Viewed by 621
Abstract
Portland cement is the most common type of cement and one of the most important ingredients in concrete. Concrete, on the other hand, is the most used building material worldwide just behind the water with an increasing usage trend in infrastructure for the [...] Read more.
Portland cement is the most common type of cement and one of the most important ingredients in concrete. Concrete, on the other hand, is the most used building material worldwide just behind the water with an increasing usage trend in infrastructure for the upcoming years. During the production process of cement, massive CO2 emissions are released into the environment, while large amounts of raw materials and energy are consumed. In the present study, Portland type cement was prepared in laboratory-scale by Greek Wet Fly Ash and Mill Scales, as well as conventional raw materials such as limestone, shale and lava. The experiments were conducted at 1450 °C and 1340 °C. The fired compositions were characterized by XRD, Q–XRD, optical microscopy, SEM/EDS and the concrete specimens were tested for their compressive strength. The results indicated that formation of cement clinker at lower temperatures (1340 °C) is feasible with the combined use of natural raw materials and industrial byproducts following the standard production route of cement industries. Finally, the so-obtained cement presented compressive strength values comparable to the conventional ones fired at 1450 °C. Full article
(This article belongs to the Special Issue Valorization of Metallurgical and Mining Residues and Wastes)
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Article
Recovery of Catapleiite and Eudialyte from Non-Magnetic Fraction of Eudialyte ore Processing of Norra Kärr Deposit
Minerals 2022, 12(1), 19; https://doi.org/10.3390/min12010019 - 23 Dec 2021
Viewed by 955
Abstract
Eudialyte ores from Norra Kärr (Sweden) and Kringlerne (Greenland) are considered a potential source of rare-earth elements (REE) for the development of a sustainable REE industry outside China. Magnetic separation is successfully applicated to recover eudialyte as a magnetic fraction. In the case [...] Read more.
Eudialyte ores from Norra Kärr (Sweden) and Kringlerne (Greenland) are considered a potential source of rare-earth elements (REE) for the development of a sustainable REE industry outside China. Magnetic separation is successfully applicated to recover eudialyte as a magnetic fraction. In the case of the Norra Kärr deposit, up to 20% of the REE and up to 40% of the Zr are lost during mineral processing in the non-magnetic fraction. Zr and REE are associated with non-magnetic minerals such as catapleiite, low- or non-magnetic eudialyte species, and both their intergrowths. Besides zirconosilicates such as catapleiite and eudialyte, the non-magnetic fraction has valuable and already-liberated minerals such as alkali feldspars and nepheline, which should not be considered as tailings. In this investigation, a possible way to recover REE bearing zirconosilicates from the non-magnetic fraction using flotation is presented. First, a low-grade eudialyte concentrate (1.8% Zr, 0.94% REE) from ground ore was obtained using magnetic separation. The non-magnetic fraction was then treated using froth flotation, and a Zr-REE bearing product (9% Zr, 1.5% REE) was obtained as froth product. For this purpose, phosphoric acid esters were used as selective collectors for zirconosilicates at a pH between 3.5 and 4.5. The reagent regime could be proposed not only to recover Zr- and REE-bearing minerals, but also simultaneously to remove Fe, Ti, and other colored impurities from the nepheline-feldspar product and to minimize the tailings volume. Full article
(This article belongs to the Special Issue Valorization of Metallurgical and Mining Residues and Wastes)
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Article
Renewable-Resource Technologies in Mining and Metallurgical Enterprises Providing Environmental Safety
Minerals 2021, 11(10), 1145; https://doi.org/10.3390/min11101145 - 18 Oct 2021
Cited by 8 | Viewed by 651
Abstract
The article addresses the issue of mining and industrial waste stored in tailings and heaps in mining areas, and it explores the existing, as well as new, ways of reducing its harmful impact on the environment. On the basis of the Russian experience [...] Read more.
The article addresses the issue of mining and industrial waste stored in tailings and heaps in mining areas, and it explores the existing, as well as new, ways of reducing its harmful impact on the environment. On the basis of the Russian experience in mining industry in Ural, it presents a process which makes it possible to eliminate the amassed hazardous waste, retrieve the valuable material (metals) stored in it, and use the remaining waste as backfill in order to both: store it underground (and not on the surface) and prevent the disasters caused by the collapse of the abandoned shafts, thus prolonging the functioning of the mining areas. The process includes preliminary activation treatment of materials found in industrial waste in a disintegrator to protect the environment from toxic pollution. The promising results of the experiment have been discussed, taking into account the complexities of economic evaluation of the idea. Full article
(This article belongs to the Special Issue Valorization of Metallurgical and Mining Residues and Wastes)
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Article
Occurrence and Leaching Behavior of Chromium in Synthetic Stainless Steel Slag Containing FetO
Minerals 2021, 11(10), 1055; https://doi.org/10.3390/min11101055 - 28 Sep 2021
Viewed by 531
Abstract
Stainless steel slag has been applied to other silicate materials due to its CaO-SiO2-based system. This is done to improve the utilization rate of stainless steel slag and apply it more safely. This paper investigated the occurrence of chromium in synthetic [...] Read more.
Stainless steel slag has been applied to other silicate materials due to its CaO-SiO2-based system. This is done to improve the utilization rate of stainless steel slag and apply it more safely. This paper investigated the occurrence of chromium in synthetic stainless steel slag containing FetO and its leaching behavior. The phase composition of the equilibrium reaction was calculated by FactSage 7.3 Equlib module. XRD, SEM-EDS and IPP 6.0 were used to investigate the phase compositions, microstructure and count the size of spinel crystals. The results indicate that the increase of Fe2O3 content can promote the precipitation of spinel phases and effectively inhibit the formation and precipitation of α-C2S in a CaO-SiO2-MgO-Cr2O3-Al2O3-FeO system. Fe2O3 contents increased from 2 wt% to 12 wt%, and the crystal size increased from 4.01 μm to 6.06 μm, with a growing rate of 51.12%. The results of SEM line scanning show the Cr-rich center and Fe-rich edge structure of the spinel phase. Comparing the TRGS 613 standard with the HJ/T 299-2007 standard, the leaching of Cr6+ in the FetO samples is far lower than the standards’ limit, and the minimum concentration is 0.00791 mg/L in 12 wt% Fe2O3 samples. Full article
(This article belongs to the Special Issue Valorization of Metallurgical and Mining Residues and Wastes)
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Article
Feasibility Study on the Potential Replacement of Primary Raw Materials in Traditional Ceramics by Clayey Overburden Sterile from the Prosilio Region (Western Macedonia, Greece)
Minerals 2021, 11(9), 961; https://doi.org/10.3390/min11090961 - 02 Sep 2021
Viewed by 750
Abstract
The objective of this study was to investigate the valorization potential of clayey overburden sterile materials from lignite-mining activities in the manufacturing of traditional ceramics. This study aims to contribute toward the sustainable management and use of such waste materials in line with [...] Read more.
The objective of this study was to investigate the valorization potential of clayey overburden sterile materials from lignite-mining activities in the manufacturing of traditional ceramics. This study aims to contribute toward the sustainable management and use of such waste materials in line with the environmental objectives of the 2030 agenda. To assess this issue, clayey steriles were incorporated in a white clay-body at 20, 50, and 80 wt%, whereas reference samples were also formed from the individual raw materials. Laboratory processing of the ceramics was performed by dry pressing loose powder into rectangular samples and firing at 1000 °C for 4 h. Characterization of the raw materials included chemical, mineralogical, and thermal analysis. The fired bodies were tested for their total linear shrinkage, apparent porosity, water absorption, bulk density, and bending strength according to the relevant standards. The microstructural evolution of the final bodies was analyzed by scanning electron microscopy, which observed differences related to the addition of the steriles. The results showed that the tested clayey steriles can be utilized up to 50 wt% as a secondary raw material in the production of ceramic materials (e.g., bricks) with comparable properties to the reference clay-bodies. Furthermore, the color of the final samples changed from white-creamy to reddish as the content of clayey sterile materials increased in the raw mix. Full article
(This article belongs to the Special Issue Valorization of Metallurgical and Mining Residues and Wastes)
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Article
Leaching of Ca-Rich Slags Produced from Reductive Smelting of Bauxite Residue with Na2CO3 Solutions for Alumina Extraction: Lab and Pilot Scale Experiments
Minerals 2021, 11(8), 896; https://doi.org/10.3390/min11080896 - 19 Aug 2021
Cited by 3 | Viewed by 839
Abstract
Sustainable utilization of Bauxite Residue (BR) is currently one of the greatest challenges being tackled by the alumina industry, due to its high production rates and limited reuse options. The present work is concerned with the use of BR as a candidate metallurgical [...] Read more.
Sustainable utilization of Bauxite Residue (BR) is currently one of the greatest challenges being tackled by the alumina industry, due to its high production rates and limited reuse options. The present work is concerned with the use of BR as a candidate metallurgical raw material for iron (Fe) production and aluminum (Al) extraction. In more detail, at first, BR undergoes reductive smelting to extract its Fe content and produce a slag of mainly calcium aluminate composition. In a second step, Al contained in the calcium aluminate phases is extracted hydrometallurgically by leaching with a Na2CO3 aqueous solution. The focus of the current study is the optimization of this leaching process, and it was performed in two stages. The first was a laboratory scale investigation on the main parameters affecting the extraction rate of Al. The second stage was performed in pilot scale and incorporated observations and suggestions based on the laboratory scale investigation. Laboratory work showed that more than 50% of aluminum could be easily extracted in less than 1 h, in 5% S/L, at 70 °C and with an 20% excess of Na2CO3. Pilot scale work, by successfully applying the suggestions derived from laboratory scale work, achieved an average Al extraction of 68% from a 10% S/L pulp, with a slag of optimized composition in relation to the one used in the laboratory scale. Full article
(This article belongs to the Special Issue Valorization of Metallurgical and Mining Residues and Wastes)
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Article
Innovative Reuse of Electric Arc Furnace Slag as Filler for Different Polymer Matrixes
Minerals 2021, 11(8), 832; https://doi.org/10.3390/min11080832 - 30 Jul 2021
Cited by 4 | Viewed by 939
Abstract
The European steel industry produces about 70 million tons/year of steel by the electric arc furnace (EAF). The slag consists of about 15% by weight of the produced steel, thus from the perspective of the circular economy, it has a high potential as [...] Read more.
The European steel industry produces about 70 million tons/year of steel by the electric arc furnace (EAF). The slag consists of about 15% by weight of the produced steel, thus from the perspective of the circular economy, it has a high potential as a co-product. This research aims to assess an innovative reuse of EAF slag as filler in different polymer matrixes: thermoplastic (polypropylene), thermosetting (epoxy resin), elastomeric (nitrile butadiene rubber), and recycled end of life rubber tire. A comparison between neat polymer and polymer filled with a certain amount of EAF slag has been carried out by tensile (or flexural), compression, and hardness tests. Experimental results show that slag as a filler increases the composites’ hardness and elastic modulus at the expense of toughness. For a safe reuse of the slag, the leaching of hazardous elements must comply with current legislation. It was found that, although the used EAF slag releases small amounts of Cr, Mo, and V, incorporating it into a polymer matrix reduces the leaching. The EAF slag particles distribution has been observed by scanning electron microscopy (SEM) images. The obtained results show good technical feasibility of this innovative slag application so that it could pave the way to a new industrial symbiosis between dissimilar sectors, bringing economic and environmental benefits. Full article
(This article belongs to the Special Issue Valorization of Metallurgical and Mining Residues and Wastes)
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Article
Creation of Backfill Materials Based on Industrial Waste
Minerals 2021, 11(7), 739; https://doi.org/10.3390/min11070739 - 07 Jul 2021
Cited by 14 | Viewed by 1042
Abstract
The possibility of replacing the traditional components of the filling mass with man-made waste and the need for the use of mechanical activation of the components of the filling composite in order to improve its rheological characteristics and the strength of the mass [...] Read more.
The possibility of replacing the traditional components of the filling mass with man-made waste and the need for the use of mechanical activation of the components of the filling composite in order to improve its rheological characteristics and the strength of the mass after solidification are proved. The demand for resource-reproducing technologies that allow the most complete use of the industrial mineral resource potential of the mining and processing enterprise, which will lead to a multiplicative ecological and economic effect, is confirmed. It is necessary to introduce the re-processing of man-made waste in order to further extract the useful component to a level that meets the standards of environmental safety and economic feasibility, which would create conditions for the actual sustainable development and give some perspectives for extending the operating time of mining regions. It is established that the sustainable development of the mining and processing region is impossible without a highly efficient exploitation of natural deposits and man-made georesources in combination with an integrated approach to the development of subsurface resources. Full article
(This article belongs to the Special Issue Valorization of Metallurgical and Mining Residues and Wastes)
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Article
Nepheline Syenite as an Alternative Source for Aluminum Production
Minerals 2021, 11(7), 734; https://doi.org/10.3390/min11070734 - 06 Jul 2021
Cited by 4 | Viewed by 1113
Abstract
The increasing demand for aluminum in conjunction with the limited available bauxite deposits in Europe results in the dire need for the evaluation of alternative raw materials for the whole value chain of alumina production. The present paper focuses on the possible use [...] Read more.
The increasing demand for aluminum in conjunction with the limited available bauxite deposits in Europe results in the dire need for the evaluation of alternative raw materials for the whole value chain of alumina production. The present paper focuses on the possible use of nepheline syenite, originated as a mine byproduct, in alumina production through leaching with an azeotropic HCl solution. Previous work on nepheline syenite dissolution focused more on the extraction of potassium and sodium values. In this work, emphasis is given at the characteristics and leachability of aluminum content phases by applying a high temperature HCl leaching in untreated material. From this point of view, leaching experiments were conducted on nepheline syenite, at a temperature range of 90 °C to 150 °C and with aqueous azeotropic HCl solution. Leaching, in the aforementioned conditions, is a process, characterized by medium aluminum dissolution. The results show that the aluminum-bearing phases that withstand the dissolution process are mainly the ones of sodium and potassium feldspars. Full article
(This article belongs to the Special Issue Valorization of Metallurgical and Mining Residues and Wastes)
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Article
Production, Properties and Performance of Slag-Based, Geopolymer Foams
Minerals 2021, 11(7), 732; https://doi.org/10.3390/min11070732 - 06 Jul 2021
Cited by 3 | Viewed by 890
Abstract
This paper demonstrates the transformation of the industrial residue (copper slag) of a Swedish mining and smelting company “Boliden”, through geopolymerization, into advanced building materials. The main objective of this experimental study is the assessment of the appropriate conditions for the preparation of [...] Read more.
This paper demonstrates the transformation of the industrial residue (copper slag) of a Swedish mining and smelting company “Boliden”, through geopolymerization, into advanced building materials. The main objective of this experimental study is the assessment of the appropriate conditions for the preparation of alkali-activated slag-based geopolymer pastes with further foaming production, by aluminum powder addition. The alkaline-activating solution used was KOH, at a constant concentration (8 M). The effect of crucial operating parameters, such as S/L ratio (3.5–4.5 g/mL) and aluminum powder addition (0.12%–0.22%), on the geopolymer paste were studied, in order to achieve the optimum rheological conditions of the slurry. The physical properties of the materials were examined after the appropriate curing process (24 h at 70 °C), with density values ranging between 805 and 1100 kg/m3. The mechanical performance of the materials ranged between 1.28 and 2 MPa (compressive strength), and from 0.25 to 0.85 MPa (flexural strength), indicating the strong correlation of physical and mechanical properties. To assess the porosity and the size distribution of the voids, image processing techniques were applied on digital images of selected samples. According to these results, the synthesized materials exhibit similar, or even better, properties than the current concrete porous materials. Full article
(This article belongs to the Special Issue Valorization of Metallurgical and Mining Residues and Wastes)
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Article
Recovery of Iron from Mill Scale by Reduction with Carbon Monoxide
Minerals 2021, 11(5), 529; https://doi.org/10.3390/min11050529 - 17 May 2021
Cited by 1 | Viewed by 1153
Abstract
The mill scale is a waste from the iron and steel industry. Due to the high content of iron in the form of oxides, it is an attractive material for the recovery of metallic iron by reduction. The product of mill scale reduction [...] Read more.
The mill scale is a waste from the iron and steel industry. Due to the high content of iron in the form of oxides, it is an attractive material for the recovery of metallic iron by reduction. The product of mill scale reduction is an iron with a very extended surface and a high affinity for oxygen. The smaller iron particles are, the easier it is for spontaneous rapid oxidation, which can be linked to pyrophoricity. This article presents results of experiments using the TG/DTA thermal analysis method aimed at verifying the possibility of recovering iron from the mill scale by a reduction with carbon monoxide at 850 °C, 950 °C, and 1050 °C, taking into account the phenomenon of secondary oxidation in contact with oxygen from air at temperatures of 300 °C, 350 °C, and 400 °C. Two forms of mill scale were used for tests, in the original state and after grinding to develop the surface. Full article
(This article belongs to the Special Issue Valorization of Metallurgical and Mining Residues and Wastes)
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Article
Experimental Evaluation of PM Emission from Red Mud Basins Exposed to Wind Erosion
Minerals 2021, 11(4), 405; https://doi.org/10.3390/min11040405 - 13 Apr 2021
Cited by 5 | Viewed by 1026
Abstract
The disposal of industrial and mineral processing residues represents a major concern for human health and the environment as a whole. In order to reduce the impact on soil and groundwater due to the waste leachability, the implementation of environmental regulations worldwide has [...] Read more.
The disposal of industrial and mineral processing residues represents a major concern for human health and the environment as a whole. In order to reduce the impact on soil and groundwater due to the waste leachability, the implementation of environmental regulations worldwide has favored the conversion of the disposal techniques from wet to dry (i.e., dry stacking or dry disposal). Such a change in the storage practice may cause the increase of particulate matter (PM) emission from the dry surfaces of the tailings exposed to wind erosion. Considering the significance of the environmental issue on a global scale and the increasingly stricter orientation of environmental policies, the need for modeling tools capable of estimating the contribution of tailing basins to air pollution becomes apparent. The paper deals with the disposal of red mud resulting from the bauxite processing in the alumina industry. An experimental research was carried with an environmental wind tunnel to estimate the Emission Factor (EF) of the basin surfaces as a function of the main affecting variables (i.e., residue water content and wind velocity). The article reports the results of the experimental test carried out on the red mud from a major basin located in Sardinia (Italy). Full article
(This article belongs to the Special Issue Valorization of Metallurgical and Mining Residues and Wastes)
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Article
Critical Minerals from Post-Processing Tailing. A Case Study from Bangka Island, Indonesia
Minerals 2021, 11(4), 352; https://doi.org/10.3390/min11040352 - 28 Mar 2021
Cited by 9 | Viewed by 1814
Abstract
The growing demand for critical raw materials (rare earth elements—REE, Nb, Ta, and others) enforces a need to look for their alternative sources. Distortions of the mineral supply chain caused by COVID-19 have necessitated a re-evaluation of what exists as mining waste from [...] Read more.
The growing demand for critical raw materials (rare earth elements—REE, Nb, Ta, and others) enforces a need to look for their alternative sources. Distortions of the mineral supply chain caused by COVID-19 have necessitated a re-evaluation of what exists as mining waste from previous exploitation. Consequently, this study aims to provide an inventory of raw materials on the Indonesian Tin Islands (Bangka and Belitung). Geological and mineralogical examinations on Bangka have permitted an economic appraisal of tailings from the processing of cassiterite-bearing sands and confirmed the presence of REE-bearing minerals, chiefly monazite and xenotime, zircon, ilmenite, rutile, niobium-tantalum phases. In general, the mineral content of the tailings varies depending on the sampling site and the type of processing used during ore-production. ICP-MS (inductively coupled plasma–mass spectrometers) analyses revealed anomalous concentrations of LREE (light rare earth elements): La > 5%, Ce > 5%, Pr > 1%, Nd > 1%, Sm > 1% and HREE+Y (heavy rare earth elements and yttrium) up to 2.51 wt%. High values have been found for the “most critical” metals of the HREE group: Dy (up to 0.34 wt%), Tb (up to 0.08 wt%), Eu (up to 61.8 ppm), Nd (>1.0 wt%), and Y (up to 1.20 wt%). In addition, the following contents have been defined: Ga (to 0.03 wt%); Hf (to 0.64 wt%); Ta (to 0.08 wt%); Nb (to 0.23 wt%); W (to 0.14 wt%); Zr (>5.0 wt%); and Sc (to 0.01 wt%). Such high concentrations suggest the tailing dumps to be a potential new source of “critical raw materials”. Full article
(This article belongs to the Special Issue Valorization of Metallurgical and Mining Residues and Wastes)
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Review

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Review
A Review of Tungsten Resources and Potential Extraction from Mine Waste
Minerals 2021, 11(7), 701; https://doi.org/10.3390/min11070701 - 29 Jun 2021
Cited by 10 | Viewed by 1553
Abstract
Tungsten is recognized as a critical metal due to its unique properties, economic importance, and limited sources of supply. It has wide applications where hardness, high density, high wear, and high-temperature resistance are required, such as in mining, construction, energy generation, electronics, aerospace, [...] Read more.
Tungsten is recognized as a critical metal due to its unique properties, economic importance, and limited sources of supply. It has wide applications where hardness, high density, high wear, and high-temperature resistance are required, such as in mining, construction, energy generation, electronics, aerospace, and defense sectors. The two primary tungsten minerals, and the only minerals of economic importance, are wolframite and scheelite. Secondary tungsten minerals are rare and generated by hydrothermal or supergene alteration rather than by atmospheric weathering. There are no reported concerns for tungsten toxicity. However, tungsten tailings and other residues may represent severe risks to human health and the environment. Tungsten metal scrap is the only secondary source for this metal but reprocessing of tungsten tailings may also become important in the future. Enhanced gravity separation, wet high-intensity magnetic separation, and flotation have been reported to be successful in reprocessing tungsten tailings, while bioleaching can assist with removing some toxic elements. In 2020, the world’s tungsten mine production was estimated at 84 kt of tungsten (106 kt WO3), with known tungsten reserves of 3400 kt. In addition, old tungsten tailings deposits may have great potential for exploration. The incomplete statistics indicate about 96 kt of tungsten content in those deposits, with an average grade of 0.1% WO3 (versus typical grades of 0.3–1% in primary deposits). This paper aims to provide an overview of tungsten minerals, tungsten primary and secondary resources, and tungsten mine waste, including its environmental risks and potential for reprocessing. Full article
(This article belongs to the Special Issue Valorization of Metallurgical and Mining Residues and Wastes)
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