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Special Issue "Advances in Mineral Processing, Waste Recycling and Extractive Metallurgy"

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A special issue of Materials (ISSN 1996-1944). This special issue belongs to the section "Advanced Materials Characterization".

Deadline for manuscript submissions: closed (20 July 2023) | Viewed by 8480

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Special Issue Editors

Dr. Alex Kondratiev

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Guest Editor

College of Environmentally Sound Technologies & Engineering, National University of Science & Technology (MISIS), Moscow, Russia
Interests: coal ash slags; thermodynamics; phase equilibria; SiO₂-Al₂O₃-CaO-'FeO' system; slag viscosity; liquid metals; smelting processes; metallurgical waste utilization
Special Issues, Collections and Topics in MDPI journals

Dr. Dmitry Valeev

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Guest Editor

Vernadsky Institute of Geochemistry and Analytical Chemistry of Russian Academу of Sciences, Moscow 119991, Russia
Interests: coal fly ash; high-silica bauxite; red mud; bauxite residue;aluminium dross; alumina production; coagulant polyaluminum chloride; high-pressure acid leaching (HPAL); flotation; magnetic separation; carbothermic reduction; mineral processing; non-ferrous metals extraction; waste utilization.
Special Issues, Collections and Topics in MDPI journals

Dr. Jinhe Pan

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Guest Editor

Key Laboratory of Coal Processing and Efficient Utilization, Ministry of Education, School of Chemical Engineering and Technology, China University of Mining and Technology, Xuzhou 221116, China
Interests: mineral processing; trace elements occurrence; hydrometallurgy; critical raw materials; utilization of coal combustion waste
Special Issues, Collections and Topics in MDPI journals

Special Issue Information

Dear Colleagues,

The permanent growth of the world economy and industry stimulates a constantly increasing production of ferrous and non-ferrous metals, while the depletion of natural resources leads to demands for the development of new technologies for the processing of low-grade ores and for deep recycling of metallurgical and other anthropogenic wastes. These new technologies in materials processing and waste recovery will play a major role in creating a sustainable future for humankind.

This Special Issue is devoted to the most relevant research in the pyro- and hydrometallurgy methods for extraction and recycling of ferrous and non-ferrous metals, including related studies of the chemical/phase composition and physical properties of the obtained products (concentrates, slags, metals, oxides, solutions, salts, etc.).

Dr. Alex Kondratiev
Dr. Dmitry Valeev
Dr. Jinhe Pan
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. Materials is an international peer-reviewed open access semimonthly 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 2600 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

bauxite
titanomagnetite
classification
magnetic separation
flotation
hydrometallurgy
acid or alkali leaching
bio-hydrometallurgy
resin sorption
solvent extraction
ionic liquids
crystallization
precipitation
pyrometallurgy
preliminary roasting
reductive smelting
calcination
rare-earth element (REE) ores
thermodynamics and kinetics
green chemistry/process
waste management
low-grade resources
slag
coal gangue
electric arc furnace
red mud
tailings
coal fly ash
aluminum dross
industrial wastes and by-products

Published Papers (10 papers)

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Research

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Open AccessArticle

Extraction of Germanium from Low-Grade Germanium-Bearing Lignite by Reductive Volatilization

and

Materials 2023, 16(15), 5374; https://doi.org/10.3390/ma16155374 - 31 Jul 2023

Viewed by 292

Abstract

Germanium (Ge) as an important strategic metal is widely used in many modern-technology fields such as optical fiber and thermal solar cells. In this study, the volatilization behavior of Ge from low-grade germanium-bearing lignite was investigated in detail through reductive volatilization. The results indicated that temperature and air flow rate in the semi-closed roasting system played a significant role in the process. The optimal volitation efficiency of Ge reached 98% at 1100 °C for 2 h with air flow rate of 0.7 L/min in a maffle furnace, respectively. Under optimal conditions, the contents of Ge lowered to 30 ppm in the roasting residue. Analysis of the enriched ash yielded 71,600 ppm for Ge. Chemical phase analysis of the Ge in the enrichment ash showed that soluble Ge accounted for 82.18% of the total Ge, which could be viewed as an excellent material for Ge extraction by chlorinated distillation. Full article

(This article belongs to the Special Issue Advances in Mineral Processing, Waste Recycling and Extractive Metallurgy)

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Open AccessArticle

Thermodynamic and Kinetic Aspects of Gold Adsorption in Micrometric Activated Carbon and the Impact of Their Loss in Adsorption, Desorption, and Reactivation Plants

Rodrigo Martínez-Peñuñuri

Jose R. Parga-Torres

Jesus L. Valenzuela-García

Héctor J. Díaz-Galaviz

Gregorio González-Zamarripa

and

Alejandro M. García-Alegría

Materials 2023, 16(14), 4961; https://doi.org/10.3390/ma16144961 - 12 Jul 2023

Viewed by 533

Abstract

The production and loss of fine particles of activated carbon (AC) loaded with gold in the adsorption processes is a worldwide problem, mainly due to the behavior of increasing its adsorption capacity with respect to the decrease in particle size, which becomes relevant to determine the thermodynamic and kinetic activity of the gold adsorption and the economic impact of its loss, with the escape towards the later stages of the system of adsorption, desorption, and reactivation (ADR) plants of AC. Through the adsorption of gold in a synthetic medium with sodium cyanide concentration, using different particle sizes, AC weights, and adsorption times, data were generated for analysis by three different isotherm models, resulting in a better tendency for the Freundlich isotherm, from which thermodynamic parameters of ΔG equal to −2.022 kcal/mol, ΔH equal to −16.710 kcal/mol, and ΔS equal to −0.049 kcal/molK were obtained, which shows that it is a spontaneous, exothermic process with a lower degree of disorder. The kinetic analysis was performed with two different models, from which the pseudo-second-order model was used due to a better tendency and displayed a behavior that leaves open the interpretation of the increase in adsorption with respect to the decrease in the AC particle size but demonstrated the importance of recovering these particles in relation to their gold concentration and the economic impact from their poor recovery, which, for this case study, amounted to ~0.3 million dollars per year. Full article

(This article belongs to the Special Issue Advances in Mineral Processing, Waste Recycling and Extractive Metallurgy)

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Open AccessArticle

Low-Temperature Treatment of Boehmitic Bauxite Using the Bayer Reductive Method with the Formation of High-Iron Magnetite Concentrate

and

Materials 2023, 16(13), 4678; https://doi.org/10.3390/ma16134678 - 28 Jun 2023

Viewed by 404

Abstract

The Bayer process is the main method of alumina production worldwide. The use of low-quality bauxites for alumina production results in the formation of a significant amount of technogenic waste—bauxite residue (BR). The Bayer reductive method is one possible way to eliminate BR stockpiling, but it requires high-pressure leaching at temperatures higher than 220 °C. In this research, the possibility of boehmitic bauxite atmospheric pressure leaching at both the first and second stages or high-pressure leaching at the second stage with the simultaneous reduction of hematite to magnetite was investigated. Bauxite and solid residue after NaOH leaching were characterized using XRD, SEM-EDS, and Mössbauer spectroscopy methods. The first stage of leaching under atmospheric pressure with the addition of Fe(II) species in a strong alkali solution (330–400 g L^–1 Na₂O) resulted in a partial reduction of the iron minerals and an extraction of more than 60% of Si and 5–25% of Al (depending on caustic modulus of solution) after 1 h. The obtained desilicated bauxite was subjected to atmospheric leaching at 120 °C in a strong alkali solution (350 g L⁻¹) or high-pressure leaching at 160–220 °C using the Bayer process mother liquor in order to obtain a concentrate with a magnetite content higher than 83 wt. %. Full article

(This article belongs to the Special Issue Advances in Mineral Processing, Waste Recycling and Extractive Metallurgy)

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Open AccessArticle

Maximizing the Recycling of Iron Ore Pellets Fines Using Innovative Organic Binders

and

Materials 2023, 16(10), 3888; https://doi.org/10.3390/ma16103888 - 22 May 2023

Cited by 1 | Viewed by 892

Abstract

This research work focuses on the practicality of using organic binders for the briquetting of pellet fines. The developed briquettes were evaluated in terms of mechanical strength and reduction behavior with hydrogen. A hydraulic compression testing machine and thermogravimetric analysis were incorporated into this work to investigate the mechanical strength and reduction behavior of the produced briquettes. Six organic binders, namely Kempel, lignin, starch, lignosulfonate, Alcotac CB6, and Alcotac FE14, in addition to sodium silicate, were tested for the briquetting of pellet fines. The highest mechanical strength was achieved using sodium silicate, Kempel, CB6, and lignosulfonate. The best combination of binder to attain the required mechanical strength even after 100% reduction was found to be a combination of 1.5 wt.% of organic binder (either CB6 or Kempel) with 0.5 wt.% of inorganic binder (sodium silicate). Upscaling using an extruder gave propitious results in the reduction behavior, as the produced briquettes were highly porous and attained pre-requisite mechanical strength. Full article

(This article belongs to the Special Issue Advances in Mineral Processing, Waste Recycling and Extractive Metallurgy)

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Open AccessArticle

Effect of the Molecular Weight of Carboxymethyl Cellulose on the Flotation of Chlorite

Yanfei Chen

Yuanlin Chen

and

Lei Zhang

Materials 2023, 16(9), 3356; https://doi.org/10.3390/ma16093356 - 25 Apr 2023

Viewed by 603

Abstract

The present study aimed to investigate the influence mechanism of carboxymethyl cellulose (CMC) on the flotation of fine chlorite. To this end, a series of flotation tests, sedimentation tests, and microscope analyses were conducted. Flotation tests revealed an inverse relationship between particle size and the recovery of chlorite, indicating that finer particles exhibited higher recovery rates. Moreover, it was observed that the recovery of fine chlorite was significantly associated with the water recovery (proportion of water entering the floated product to the weight of water in the initial flotation suspension) and a variety of frother types. Based on these findings, it can be inferred that froth entrainment may constitute a crucial component of the recovery mechanism underlying fine chlorite. Thus, reducing froth entrainment (the phenomenon of hydrophilic minerals entering floated products through foam water) is the key to depress chlorite flotation. Flotation tests indicate that fine chlorite recovered into froth products can be depressed effectively by CMC with a high molecular weight. The results of sedimentation tests and microscope analyses in the presence of CMC prove that CMC with a high molecular weight generates flocculation on fine chlorite particles while that with a low molecular weight does not. It is suggested that the depression of chlorite flotation may be attributed to the reduction in the entrainment resulting from the flocculation induced by CMC. Full article

(This article belongs to the Special Issue Advances in Mineral Processing, Waste Recycling and Extractive Metallurgy)

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Open AccessArticle

Complex Formation of Rare-Earth Elements in Carbonate–Alkaline Media

Tatiana Litvinova

Ruslan Kashurin

and

Denis Lutskiy

Materials 2023, 16(8), 3140; https://doi.org/10.3390/ma16083140 - 16 Apr 2023

Cited by 1 | Viewed by 892

Abstract

Rare earth metals are critical components for many industries. The extraction of rare earth metals from mineral raw materials presents many problems, both of a technological and theoretical nature. The use of man-made sources imposes strict requirements on the process. Thermodynamic and kinetic data that could describe the most detailed technological water–salt leaching and precipitation systems are insufficient. The study addresses the problem of a small amount of data on the formation and equilibrium of carbonate–alkali systems of rare earth metals. Isotherms of solubility of sparingly soluble carbonates with the formation of carbonate complexes are presented to evaluate equilibrium constants logK at zero ionic strength for Nd −11.3, Sm −8.6, Gd −8.0, and Ho −7.3. To accurately predict the system under consideration, a mathematical model was developed, which allows to calculate the water–salt composition. The initial data for calculation are concentration constants of stability of lanthanide complexes. This work will contribute to deepening knowledge about rare earth elements extraction problems and will serve as a reference for studying the thermodynamics of water–salt systems. Full article

(This article belongs to the Special Issue Advances in Mineral Processing, Waste Recycling and Extractive Metallurgy)

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Open AccessArticle

Co-Carbonization of Discard Coal with Waste Polyethylene Terephthalate towards the Preparation of Metallurgical Coke

and

Materials 2023, 16(7), 2782; https://doi.org/10.3390/ma16072782 - 30 Mar 2023

Viewed by 1193

Abstract

Waste plastics such as polyethylene terephthalate (w-PET) and stockpiled discard coal (d-coal) pose a global environmental threat as they are disposed of in large quantities as solid waste into landfills and are particularly hazardous due to spontaneous combustion of d-coal that produces greenhouse gases (GHG) and the non-biodegradability of w-PET plastic products. This study reports on the development of a composite material, prepared from w-PET and d-coal, with physical and chemical properties similar to that of metallurgical coke. The w-PET/d-coal composite was synthesized via a co-carbonization process at 700 °C under a constant flow of nitrogen gas. Proximate analysis results showed that a carbonized w-PET/d-coal composite could attain up to 35% improvement in fixed carbon content compared to its d-coal counterpart, such that an initial fixed carbon content of 14–75% in carbonized discard coal could be improved to 49–86% in carbonized w-PET/d-coal composites. The results clearly demonstrate the role of d-coal ash on the degree of thermo-catalytic conversion of w-PET to solid carbon, showing that the yield of carbon derived from w-PET (i.e., c-PET) was proportional to the ash content of d-coal. Furthermore, the chemical and physical characterization of the composition and structure of the c-PET/d-coal composite showed evidence of mainly graphitized carbon and a post-carbonization caking ability similar to that of metallurgical coke. The results obtained in this study show potential for the use of waste raw materials, w-PET and d-coal, towards the development of an eco-friendly reductant with comparable chemical and physical properties to metallurgical coke. Full article

(This article belongs to the Special Issue Advances in Mineral Processing, Waste Recycling and Extractive Metallurgy)

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Open AccessArticle

Quantitative Analysis of Mixed Minerals with Finite Phase Using Thermal Infrared Hyperspectral Technology

and

Materials 2023, 16(7), 2743; https://doi.org/10.3390/ma16072743 - 29 Mar 2023

Cited by 3 | Viewed by 692

Abstract

It is crucial but challenging to detect intermediate or end products promptly. Traditional chemical detection methods are time-consuming and cannot detect mineral phase content. Thermal infrared hyperspectral (TIH) technology is an effective means of real-time imaging and can precisely capture the emissivity characteristics of objects. This study introduces TIH to estimate the content of potassium salts, with a model based on Competitive Adaptive Reweighted Sampling (CARS) and Partial Least Squares Regression (PLSR). The model takes the emissivity spectrum of potassium salt into account and accurately predicts the content of Mixing Potassium (MP), a mineral mixture produced in Lop Nur, Xinjiang. The main mineral content in MP was measured by Mineral Liberation Analyzer (MLA), mainly including picromerite, potassium chloride, magnesium sulfate, and less sodium chloride. 129 configured MP samples were divided into calibration (97 samples) and prediction (32 samples) sets. The CARS-PLSR method achieved good prediction results for MP mineral content (picromerite: correlation coefficient of correction set (

R_{p}^{2}

) = 0.943, predicted root mean square error (RMSEP) = 2.72%, relative predictive deviation (RPD) = 4.24; potassium chloride:

R_{p}^{2}

= 0.948, RMSEP = 2.86%, RPD = 4.42). Experimental results convey that TIH technology can effectively identify the emissivity characteristics of MP minerals, facilitating quantitative detection of MP mineral content. Full article

(This article belongs to the Special Issue Advances in Mineral Processing, Waste Recycling and Extractive Metallurgy)

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Open AccessArticle

Rare-Earth Elements Extraction from Low-Alkali Desilicated Coal Fly Ash by (NH₄)₂SO₄ + H₂SO₄

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Materials 2023, 16(1), 6; https://doi.org/10.3390/ma16010006 - 20 Dec 2022

Cited by 3 | Viewed by 1336

Abstract

Coal fly ash (CFA) obtained from pulverized coal furnaces is a highly refractory waste that can be used for alumina and rare-earth elements (REEs) extraction. The REEs in this type of CFA are associated with a mullite and amorphous glassy mass that forms a core-shell structure. In this research, it was shown that complete dissolution of amorphous aluminosilicates from the mullite surface with the formation of the low-alkali mullite concentrate prior to sulfuric acid leaching with the addition of (NH₄)₂SO₄ helps to accelerate the extraction of REEs. The extraction degree of Sc and other REEs reaches 70–80% after 5 h of leaching at 110 °C and acid concentration of 5 M versus less than 20% for the raw CFA at the same conditions. To study the leaching kinetics of the process, the effects of temperature (90–110 °C), liquid-to-solid ratio (5–10), and leaching time (15–120 min) on the degrees of Al and rare-earth elements (REEs) extraction were evaluated. After 120 min of leaching at 110 °C and L/S ratio = 10, the extraction of Al was found to be lower than 30%. At the same time, total REEs (TREE) and Fe extraction were greater than 60%, which indicates that a part of the TREE was transferred into the acid soluble phase. After leaching, the residues were studied by laser diffraction (LD), X-ray diffraction (XRD), X-ray fluorescence (XRF), and scanning electron microscopy (SEM-EDS) to evaluate the leaching mechanism and the solubility of Al- and Fe-containing minerals, such as mullite, hematite, and amorphous aluminosilicate. Full article

(This article belongs to the Special Issue Advances in Mineral Processing, Waste Recycling and Extractive Metallurgy)

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Review

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Open AccessReview

Solvent Extraction as a Method of Recovery and Separation of Platinum Group Metals

and

Katarzyna Leszczyńska-Sejda

Materials 2023, 16(13), 4681; https://doi.org/10.3390/ma16134681 - 28 Jun 2023

Cited by 1 | Viewed by 779

Abstract

Platinum group metals (PGMs) are a group of six metals with high market value and key importance to many industrial sectors. Due to their low prevalence in the Earth’s crust and high demand, these metals have been recognized as critical materials for many years. Along with economic development, the natural resources of the platinum group metals are gradually depleting, which is accompanied by the need to recover PGMs from secondary sources. The solutions resulting from the processing of such materials are characterized by high content of impurities and low content of precious metals. For this reason, in order to obtain pure metals, it is extremely important to choose an effective, selective method for the recovery and separation of the platinum group metals. This review focuses on the most important aspects of the characteristics of the PGMs, including their properties and occurrence, the processing of natural and secondary raw materials and the role of liquid–liquid extraction in the selective separation of metals from this group, not only on a laboratory scale but, above all, on an industrial scale. In addition, this study collects information on the most commonly used, commercially available extractants, based on current reports, taken from the scientific literature. Full article

(This article belongs to the Special Issue Advances in Mineral Processing, Waste Recycling and Extractive Metallurgy)

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