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Special Issue "Extraction and Recovery of Valuable Metals from Waste and Mineral Materials"

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

Deadline for manuscript submissions: closed (20 October 2023) | Viewed by 7728

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Dr. Fiseha Tesfaye

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Guest Editor

Johan Gadolin Process Chemistry Centre, Åbo Akademi University, Henrikinkatu 2, 20500 Turku, Finland
Interests: metallurgical thermodynamics; extractive metallurgy; recycling; energy materials; circular economy; electrochemistry; chalcogenide and intermetallic materials; sulfosalts and sulfates characterizations; metallurgical engineering; metals; renewable energy
Special Issues, Collections and Topics in MDPI journals

Dr. Leiting Shen

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Guest Editor

School of Metallurgy and Environment, Central South University, Changsha 410083, China
Interests: recovery and utilization of metallurgical resources; mineral processing; extractive metallurgy; hydrometallurgy; cleaner production; metallurgical thermodynamics
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Special Issue Information

Dear Colleagues,

With an increasing pressure on environmental protection and the supply of raw materials, mineral, metallurgy and material processes are assessed in terms of their sustainability. The comprehensive utilization of the wastes generated in these processes has drawn worldwide attention from governments, industries and academics. Thus, this Special Issue on “Extraction and Recovery of Valuable Metals from Waste and Mineral Materials” aims to frame a comprehensive discussion and share data on the progress of the sustainable metallurgical processing of primary and secondary resources.

This topic invites submissions on scientific discoveries and emerging technologies that enable the sustainable extraction, processing, and separation of valuable metals from unconventional sources. Topics include but are not limited to:

Metal extraction from mine tailings, metallurgical residues, material scraps, and coal ash;
Recovery of valuable metals from acid drainage and oil field brines;
Processing and separation of valuable metals from unconventional sources;
Thermodynamics, kinetics, and modelling of sustainable processes.

Manuscripts that address advances in separations science, metals refining, process intensification, and technology scale-up are a good fit. Papers intended for a broad readership, including research, practical, review or system analyses, are especially welcome.

Dr. Fiseha Tesfaye
Dr. Leiting Shen
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. Processes 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 2400 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

metal recovery
mine tailings
metallurgical residues
material scraps
coal ash
acid drainage
oil field brines

Published Papers (7 papers)

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Research

14 pages, 3676 KiB

Open AccessArticle

Reaction Behavior of Kaolinite in Sulfur-Bearing Sodium Aluminate Solution under the Simulated Bayer Process

and

Processes 2023, 11(9), 2630; https://doi.org/10.3390/pr11092630 - 03 Sep 2023

Cited by 1 | Viewed by 541

Abstract

Over a billion tons of high-sulfur bauxite has not been utilized effectively currently in China, because the pyrite existing in the bauxite poses a range of hazards during the Bayer process. A novel idea was proposed to remove sulfur by the silicon-containing minerals in bauxite reacting with sulfur species in sodium aluminate solution to form sulfur-bearing desilication products (SDSP) for discharge with the red mud in the Bayer process. This study investigated the reaction behavior between kaolinite and different sulfur-containing ions under the simulated Bayer process conditions, elucidating the desulfurization rate variation and formation mechanism of SDSPs. The thermodynamic calculations suggest that the reaction between kaolinite and sulfur-bearing sodium aluminate solution to form SDSPs can occur spontaneously. The experimental results demonstrated that various SDSPs can be produced through the reaction of kaolinite and sulfur-containing ions in sodium aluminate solution during the simulated Bayer process, resulting in various desulfurization efficiencies, while the desulfurization process will not result in additional alkali consumption. Increasing the kaolinite dosage, extending the reaction time, and elevating the reaction temperature all contribute positively to enhancing desulfurization efficiency. Kaolinite reacted with

S_{2} O_{3}^{2 -}

in sodium aluminate solution to generate Na₈Al₆Si₆O₂₄S₂O₃·2H₂O, achieving a desulfurization rate exceeding 90% under optimized conditions. Under the simulated Bayer digestion process conditions at elevated temperature, the desulfurization rates of kaolinite ranked in ascending order as

S^{2 -}

{SO}_{3}^{2 -}

{SO}_{4}^{2 -}

S_{2} O_{3}^{2 -}

. Kaolinite reacted with

{SO}_{4}^{2 -}

and

S_{2} O_{3}^{2 -}

to form cancrinite type SDSPs, and a superior desulfurization rate can be achieved. This work can provide a theoretical foundation and technological support for the efficient utilization of high-sulfur bauxite by the Bayer process. Full article

(This article belongs to the Special Issue Extraction and Recovery of Valuable Metals from Waste and Mineral Materials)

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16 pages, 2957 KiB

Open AccessArticle

Molecular Dynamics Calculation of the Coordination Behavior of Yb (III) in Sodium Carbonate Solution

and

Processes 2023, 11(9), 2624; https://doi.org/10.3390/pr11092624 - 02 Sep 2023

Viewed by 439

Abstract

Yb (III) shows complex behavior of coordination dissolution and precipitation in carbonate solutions, but the properties of

{C O}_{3}^{2 -}

coordination and hydration to Yb (III) in the solution have not been explicated. In this work, the dissolution rule of Yb [...] Read more.

Yb (III) shows complex behavior of coordination dissolution and precipitation in carbonate solutions, but the properties of

{C O}_{3}^{2 -}

coordination and hydration to Yb (III) in the solution have not been explicated. In this work, the dissolution rule of Yb (III) with

{C O}_{3}^{2 -}

concentration has been studied. The radial distribution function and the coordination number of

{C O}_{3}^{2 -}

and

H_{2} O

to Yb (III) were calculated by molecular dynamics simulation, and the complex ion form of Yb was obtained. The ultraviolet–visible spectrum and the ionic structures of Yb (III) complex ions were geometrically optimized and calculated by using density functional theory. Then, the experimental ultraviolet–visible spectra and density functional theory results were combined to verify the molecular dynamics calculations. The results indicate that Yb (III) undergoes precipitation in low-concentration carbonate solution, but, in high-concentration carbonate solution, Yb (III)’s carbonates will undergo dissolution. The main reason for the dissolution of Yb (III)’s carbonates is the coordination effect of

{C O}_{3}^{2 -}

on Yb (III); the coordination of carbonate on Yb (III) occurs with a

{C O}_{3}^{2 -}

concentration range of 0.4~2.0 mol·

L^{- 1}

. Yb (III) mainly exhibits

{[Y b \cdot 9 H_{2} O]}^{3 +}

hydrated form in the aqueous solution, while, in the carbonate solution,

{[Y b \cdot 9 H_{2} O]}^{3 +}

is converted into

{[Y {b (C O}_{3})_{2} \cdot 5 H_{2} O]}^{-}

complex.

{[Y {b (C O}_{3})_{2} \cdot 5 H_{2} O]}^{-}

complex is the main ionic form in high-concentration carbonate solutions. The analysis method in this work provides guidance for understanding the coordination and hydration characteristics of oxyacid radicals to rare earth elements. Full article

(This article belongs to the Special Issue Extraction and Recovery of Valuable Metals from Waste and Mineral Materials)

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17 pages, 5593 KiB

Open AccessArticle

The Recovery of TiO₂ from Ilmenite Ore by Ammonium Sulfate Roasting–Leaching Process

Mahmoud S. Abdelgalil

K. El-Barawy

Yang Ge

and

Longgong Xia

Processes 2023, 11(9), 2570; https://doi.org/10.3390/pr11092570 - 28 Aug 2023

Viewed by 761

Abstract

TiO₂ production is a key part of Ti metallurgy and Ti recycling, and the process itself has turned out to be energy-consuming and material-consuming. New technologies are needed to utilize complex Ti ores, such as ilmenite, and reduce the carbon footprint of TiO₂ extraction. Ammonium sulfate roasting has been revealed as an efficient way to carry out phase transformations of complex minerals. A low-temperature sulfation roasting approach was studied to chemically breaking down the crystal structure of ilmenite and generate metal soluble sulfates simultaneously. These roasted products were introduced to water leaching, then the residue of the water leaching was leached by diluted HCl acid, and the TiO₂ product was enriched in the leaching residue. The effects of roasting temperature, roasting time, ilmenite-to-ammonium sulfate mass ratio, ilmenite particle size, and second-stage roasting on iron removal and titanium loss leaching efficiency were systematically studied. The results show that the optimum roasting conditions were a roasting temperature of 500 °C, a roasting time of 210 min, an ilmenite-to-(NH₄)₂SO₄ mass ratio of 1:7, and an ilmenite particle size of below 43 µm. Under optimized conditions, the TiO₂ grade in the obtained synthetic rutile reached 75.83 wt.%. Furthermore, the phase transformation and reaction mechanism during roasting are discussed and interpreted. Full article

(This article belongs to the Special Issue Extraction and Recovery of Valuable Metals from Waste and Mineral Materials)

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11 pages, 6349 KiB

Open AccessArticle

Anodic Behavior of Hafnium in Anhydrous Electrodissolution-Coupled Hafnium Alkoxide Synthesis

and

Processes 2023, 11(2), 564; https://doi.org/10.3390/pr11020564 - 13 Feb 2023

Viewed by 897

Abstract

The electrodissolution-coupled hafnium alkoxide (Hf(OR)₄, R is alkyl) synthesis (EHS) system, which has significant environmental and economic advantages over conventional thermal methods, serves as a promising system for green and efficient Hf(OR)₄ electro-synthesis. The EHS system is operated based on the simultaneous heterogeneous reactions of hafnium dissolution and ethanol dehydrogenation, as well as the spontaneous solution-based reaction of Hf⁴⁺ and OR⁻. Employing green ethanol and Hf as feedstocks, the anodic hafnium corrosion/dissolution electrochemical behavior of the Et₄NCl or Et₄NHSO₄ based anhydrous system was investigated through electrochemical measurements combined with SEM observations. The results demonstrated that the Et₄NCl-based anhydrous ethanol system exhibited an efficient mechanism of passive film pitting corrosion breakdown and metal hafnium dissolution, while the Et₄NHSO₄-based anhydrous ethanol system reflected the weak corrosion mechanism of the anodic hafnium under the passive film. The polarization resistance of the Et₄NCl system was dramatically lower than that of the Et₄NHSO₄ system, which indicated that the Et₄NCl system had superior anodic hafnium corrosion performance compared to the Et₄NHSO₄ system. Overall, the investigation of the electrochemical behaviors of anodic hafnium corrosion/dissolution provides theoretical guidance for the efficient operation of EHS electrolysis. Full article

(This article belongs to the Special Issue Extraction and Recovery of Valuable Metals from Waste and Mineral Materials)

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21 pages, 7014 KiB

Open AccessArticle

Co-Pyrolysis Behavior, Kinetic and Mechanism of Waste-Printed Circuit Board with Biomass

Sonalben B. Prajapati

and

Processes 2023, 11(1), 229; https://doi.org/10.3390/pr11010229 - 10 Jan 2023

Cited by 2 | Viewed by 1333

Abstract

Waste-printed circuit boards (WPCBs) account for approximately 3–6 wt% of total electronic waste. Due to their content of thermosetting materials and added brominated fire retardants, their recycling and disposal is difficult and not eco-friendly. Pyrolysis as a thermal degradation process may assist in the solution of this problem. In addition, using biomass as an additive can upgrade the bio-oil and fix bromines in the char. In this study, cotton stalk (CS) is chosen as an additive and kinetic of the pyrolysis of three samples namely: PCB, CS, and CS:PCB (50:50) were investigated by the thermogravimetric analyzer (TGA) at heating rates of 5, 10, and 15 K/min. Three non-isothermal methods: FWO, KAS, and Starink were found in good agreement with the TGA data; however, the FWO method was more efficient in the description of the degradation mechanism of solid-state reactions. For CS and CS:PCB (50:50), α was increased from 0.2 to 0.9 with the FWO method, and calculated E_α values were found in the range of 121.43–151.88 and 151.60–105.67 kJ/mol in zone 1, while 197.06–79.22 and 115.90–275.06 kJ/mol in zone 2, respectively. Whereas, for PCB in zone 1, E_α values were found to be in the range of 190.23–93.88 kJ/mol. The possible decomposition mechanism was determined by the Criado method, which was in agreement with the mechanism model for reaction order n = 3. The oil product was also analyzed using Fourier-Transform Infrared Spectroscopy analysis. Full article

(This article belongs to the Special Issue Extraction and Recovery of Valuable Metals from Waste and Mineral Materials)

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12 pages, 3599 KiB

Open AccessArticle

Leaching Behavior of the Main Metals from Copper Anode Slime during the Pretreatment Stage of the Kaldor Furnace Smelting Process

and

Processes 2022, 10(12), 2510; https://doi.org/10.3390/pr10122510 - 25 Nov 2022

Cited by 1 | Viewed by 1561

Abstract

The Kaldor furnace smelting process is currently the mainstream process for treating copper anode slime, but the existence of copper, tellurium and other impurities has adverse effects on the recovery of gold and silver during the Kaldor furnace smelting stage. Therefore, it is necessary to pretreat the copper anode slime to remove these impurities before Kaldor furnace reduction smelting. However, the current pretreatment process of copper anode slime generally has the problem of low removal efficiency of copper and tellurium, and little research on the occurrence state of main metals in copper anode slime. Therefore, this study quantitatively determined the phase composition of Cu, Te, Pb, Bi, As, Sb, Se, Ag and Au, and hydrogen peroxide was introduced to enhance the leaching of impurities. The leaching behavior of each metal in copper anode slime was investigated in detail. The results demonstrate that Cu and Te in the copper anode slime mainly exist in the form of CuO and CuSO₄ and Te and AuTe₂, respectively. More than 99% of the Cu and 97% of the Te were leached out using 250 g/L H₂SO₄ and 28.8 g/L H₂O₂ with a leaching pressure of 0.8 MPa at 150 °C for 2 h, while the leaching of Au and Ag was both < 0.03%. The removal of Cu and Te and the enrichment of precious metals were achieved. This study provides a rich theoretical reference for the optimization of the Kaldor furnace process. Full article

(This article belongs to the Special Issue Extraction and Recovery of Valuable Metals from Waste and Mineral Materials)

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16 pages, 7526 KiB

Open AccessFeature PaperArticle

Comparison of the Preparation Process of Rare Earth Oxides from the Water Leaching Solution of Waste Nd-Fe-B Magnets’ Sulfate Roasting Products

and

Processes 2022, 10(11), 2310; https://doi.org/10.3390/pr10112310 - 06 Nov 2022

Cited by 2 | Viewed by 1379

Abstract

The new process developed here consisting of sulfurization roasting transformation and water immersion can effectively realize the separation of rare earth elements (REEs) and impurities from spent Nd-Fe-B magnets. For the industrial application of the new process, it is critical to determine how to economically and efficiently prepare rare earth oxide (RE_xO_y) products with higher purity from the obtained water leaching solution. Therefore, according to rare earth sulfate (RE₂(SO₄)₃) solution characteristics, the oxalic acid precipitation–calcination method, sodium carbonate precipitation–calcination method, and double sulfates precipitation–alkali conversion–calcination method were optimized and compared. The results show that the recovery efficiency of REE recovery via the oxalic acid precipitation–calcination method is 99.44%, and the purity of RE_xO_y is 99.83% under optimal technological conditions. However, the cost of oxalic acid precipitation is higher. The process consisting of the double sulfates precipitation–alkali conversion–calcination method is relatively complicated, the recovery efficiency of REEs is 97.95%, and the purity of the RE_xO_y is 98.04%. The recovery efficiency of the REEs and the purity of the RE_xO_y obtained from the sodium carbonate precipitation–calcination method are 99.12% and 98.33%, respectively. Moreover, the recycling cost of sodium carbonate precipitation is the lowest among the three processes for preparing RE_xO_y, so it has industrial application potential. The obtained results for REE recovery from spent Nd-Fe-B magnets in this research can provide theoretical guidance for the innovation of the recycling process for REEs as secondary resources. Full article

(This article belongs to the Special Issue Extraction and Recovery of Valuable Metals from Waste and Mineral Materials)

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