Extraction and Recovery of Valuable Metals from Waste and Mineral Materials

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 14497

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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
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Guest Editor
School of Metallurgy and Environment, Central South University, Changsha 410083, China
Interests: nonferrous metallurgy; hydrometallurgy; recycling of critical metals; thermodynamics and modeling of aqueous solution
Special Issues, Collections and Topics in MDPI journals

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

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Keywords

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

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Published Papers (7 papers)

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Research

14 pages, 3676 KiB  
Article
Reaction Behavior of Kaolinite in Sulfur-Bearing Sodium Aluminate Solution under the Simulated Bayer Process
by Fei Niu, Guihua Liu, Junqiang Zhu, Jun Pan, Tiangui Qi, Saikui Wang, Xiaobin Li, Shi Wang and Youming Yang
Processes 2023, 11(9), 2630; https://doi.org/10.3390/pr11092630 - 3 Sep 2023
Cited by 3 | Viewed by 1024
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 [...] Read more.
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 S2O32 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 S2 < SO32  < SO42 < S2O32. Kaolinite reacted with SO42 and S2O32 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
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16 pages, 2957 KiB  
Article
Molecular Dynamics Calculation of the Coordination Behavior of Yb (III) in Sodium Carbonate Solution
by Qiaofa Lan, Youming Yang, Ziyu Xie, Haoran Guo, Donghui Liu and Xiaolin Zhang
Processes 2023, 11(9), 2624; https://doi.org/10.3390/pr11092624 - 2 Sep 2023
Viewed by 1015
Abstract
Yb (III) shows complex behavior of coordination dissolution and precipitation in carbonate solutions, but the properties of CO32 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 CO32 coordination and hydration to Yb (III) in the solution have not been explicated. In this work, the dissolution rule of Yb (III) with CO32 concentration has been studied. The radial distribution function and the coordination number of CO32 and H2O 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 CO32 on Yb (III); the coordination of carbonate on Yb (III) occurs with a CO32 concentration range of 0.4~2.0 mol·L1. Yb (III) mainly exhibits [Yb·9H2O]3+ hydrated form in the aqueous solution, while, in the carbonate solution, [Yb·9H2O]3+ is converted into [Yb(CO3)2·5H2O] complex. [Yb(CO3)2·5H2O] 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
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17 pages, 5593 KiB  
Article
The Recovery of TiO2 from Ilmenite Ore by Ammonium Sulfate Roasting–Leaching Process
by 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
Cited by 6 | Viewed by 2648
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 [...] Read more.
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
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11 pages, 6349 KiB  
Article
Anodic Behavior of Hafnium in Anhydrous Electrodissolution-Coupled Hafnium Alkoxide Synthesis
by Shuai Li, Shenghai Yang, Pengfei Zhao, Yongming Chen, Chaobo Tang, Yanqing Lai, Chaoyong Deng and Changhong Wang
Processes 2023, 11(2), 564; https://doi.org/10.3390/pr11020564 - 13 Feb 2023
Cited by 1 | Viewed by 1414
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 [...] Read more.
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
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21 pages, 7014 KiB  
Article
Co-Pyrolysis Behavior, Kinetic and Mechanism of Waste-Printed Circuit Board with Biomass
by Sonalben B. Prajapati, Alok Gautam, Shina Gautam, Zhitong Yao, Fiseha Tesfaye and Xiaoshu Lü
Processes 2023, 11(1), 229; https://doi.org/10.3390/pr11010229 - 10 Jan 2023
Cited by 4 | Viewed by 2196
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 [...] Read more.
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 Eα 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, Eα 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
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12 pages, 3599 KiB  
Article
Leaching Behavior of the Main Metals from Copper Anode Slime during the Pretreatment Stage of the Kaldor Furnace Smelting Process
by Hong Zeng, Fupeng Liu, Songlin Zhou, Chunfa Liao, Feixiong Chen and Yanliang Zeng
Processes 2022, 10(12), 2510; https://doi.org/10.3390/pr10122510 - 25 Nov 2022
Cited by 4 | Viewed by 2731
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 [...] Read more.
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
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16 pages, 7526 KiB  
Article
Comparison of the Preparation Process of Rare Earth Oxides from the Water Leaching Solution of Waste Nd-Fe-B Magnets’ Sulfate Roasting Products
by Feixiong Chen, Fupeng Liu, Longjun Wang and Jinliang Wang
Processes 2022, 10(11), 2310; https://doi.org/10.3390/pr10112310 - 6 Nov 2022
Cited by 8 | Viewed by 2408
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 [...] Read more.
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 (RExOy) 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 RExOy 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 RExOy is 98.04%. The recovery efficiency of the REEs and the purity of the RExOy 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 RExOy, 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
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