Hydrometallurgical Recycling of Critical Metals from End-of-Life Devices

A special issue of Recycling (ISSN 2313-4321).

Deadline for manuscript submissions: closed (15 November 2022) | Viewed by 46643

Special Issue Editor

Centro de Química Estrutural, Faculdade de Ciências, Universidade de Lisboa Campo Grande, C8 1749-016 Lisboa, Portugal
Interests: spent catalysts; metals recycling; hydrometallurgy; liquid–liquid (solvent) extraction; organic synthesis; platinum-group metals; silver; iron; chloride media
Special Issues, Collections and Topics in MDPI journals

Special Issue Information

Dear Colleagues,

The long list of technological devices used in our day-to-day life and in modern industrial plants and diverse facilities relies extensively on the use of several metals. When those devices are no longer useful, they should be processed to recycle the involved materials since most of them are scarce, harmful to the environment, and valuable. This overall situation has led European Union to prepare lists of “critical raw materials” every 3 years since 2011. The latest one from 2017 identified 27 “critical raw materials,” 17 of which are metals. Recycling of metals from spent devices should therefore be considered as a top priority.

Several recycling plants worldwide are primarily based on pyrometallurgical techniques, but hydrometallurgy arises as a possible alternative; as lower temperatures are involved, it exhibits potential for extraction of any valuable co-metals, it can be adapted to both small- and large-scale operations, and liquid effluents are usually easier to handle than the volatile combustion emissions from the pyro-based recycling sites.

This Special Issue welcomes review, original research, and case studies articles, focusing on innovative and challenging hydrometallurgical techniques particularly developed to recycle end-of life devices containing critical metals, e.g., spent industrial catalysts and catalytic converters (SCC), waste electrical and electronic equipment (WEEE), spent batteries of different kinds, end-of-life fluorescent lamps, NdFeB magnets and similar devices, waste liquid crystal displays (LCD).

Dr. Ana Paula Paiva
Guest Editor

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Keywords

  • Recycling of spent devices
  • SCC, WEEE, LCD
  • Hydrometallurgy
  • Leaching/digestion
  • Bioleaching
  • Separation and purification methods
  • solvent extraction
  • Ion exchange
  • Ionic liquids
  • Critical metals

Published Papers (9 papers)

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Research

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9 pages, 2080 KiB  
Article
Applied Tests to Select the Most Suitable Fungal Strain for the Recovery of Critical Raw Materials from Electronic Waste Powder
Recycling 2022, 7(5), 72; https://doi.org/10.3390/recycling7050072 - 05 Oct 2022
Cited by 2 | Viewed by 1903
Abstract
Electrical and electronic wastes (WEEEs) are a potential source of raw materials. The main challenge for scientists is to set up a reliable and eco-friendly process to recycle raw materials and precious elements from WEEEs. Today, we know that fungi could play an [...] Read more.
Electrical and electronic wastes (WEEEs) are a potential source of raw materials. The main challenge for scientists is to set up a reliable and eco-friendly process to recycle raw materials and precious elements from WEEEs. Today, we know that fungi could play an active role in green technologies aimed at recycling valuable elements. The bioaccumulation mechanism and bioleaching activity of filamentous fungal species have already been exploited fruitfully in extraction processes. However, not all fungal strains possess the same characteristics, and it is crucial to choose the right strains to use. In this work, we show a method to assess the precious elements’ recovery efficiency from WEEE using fungal strains. A CAS agar screening test for siderophore detection was carried out with three strains. The following plate accumulation test performed on a medium added with 120 ppm of electronic waste powder highlighted the differences in accumulation capability, growth rate, and biomass production. Among the elements in tested waste, yttrium, copper, and palladium show the highest bioconcentration factor. The results confirm the biotechnological potential of fungi to recover valuable elements at the bench scale, highlighting the importance of effective screening tests to assess the most efficient strain for each kind of waste. Full article
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12 pages, 2060 KiB  
Article
Application of Electrodialysis for the Selective Lithium Extraction Towards Cobalt, Nickel and Manganese from Leach Solutions Containing High Divalent Cations/Li Ratio
Recycling 2022, 7(2), 14; https://doi.org/10.3390/recycling7020014 - 02 Mar 2022
Cited by 7 | Viewed by 3446
Abstract
The present work aims at investigating the potentialities of implementation of electrodialysis for the recycling of spent lithium-ion batteries. In this work, the use of highly-selective membrane toward lithium(I) in electrodialysis was investigated to recover selectively lithium(I) toward cobalt(II), nickel(II) and manganese(II) by [...] Read more.
The present work aims at investigating the potentialities of implementation of electrodialysis for the recycling of spent lithium-ion batteries. In this work, the use of highly-selective membrane toward lithium(I) in electrodialysis was investigated to recover selectively lithium(I) toward cobalt(II), nickel(II) and manganese(II) by means of monovalent ion-selective membranes. It was shown that the presence of divalent cations in the leach solution is responsible for a significant decrease of the limiting current despite an increase in ionic conductivity. Therefore, monitoring the ionic conductivity was not sufficient to operate electrodialysis under optimal conditions, especially when highly selective membranes were used. Furthermore, it was demonstrated that the current has to be lower than the limiting current to avoid metal hydroxide precipitation into the membrane porosity by monitoring the limiting current over time. Full article
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13 pages, 3535 KiB  
Article
Recovery of Ag, Au, and Pt from Printed Circuit Boards by Pressure Leaching
Recycling 2021, 6(4), 67; https://doi.org/10.3390/recycling6040067 - 13 Oct 2021
Cited by 7 | Viewed by 3037
Abstract
Reclamation of printed circuit boards (PCBs) to recover metals is gaining growing attention due to minerals being non-renewable resources. Currently, metals extraction from PCBs through an efficient and green method is still under investigation. The present investigation concerns the recycling of printed circuit [...] Read more.
Reclamation of printed circuit boards (PCBs) to recover metals is gaining growing attention due to minerals being non-renewable resources. Currently, metals extraction from PCBs through an efficient and green method is still under investigation. The present investigation concerns the recycling of printed circuit boards using hydrometallurgical processes. First, the basic metals (Cu, Ni, Zn and Fe) were separated using a sulfuric acid solution at moderate temperatures. The remaining solids were characterized by SEM-EDS, whereby a high content of precious metals (Au, Ag and Pt) was observed. In the second stage, solids were leached with a solution of HCl and NaClO in a 1-L titanium reactor with varied oxygen pressure (0.2, 0.34 and 0.55 MPa), temperature (40, 50 and 80 °C) and concentration of HCl (2 and 4 M), obtaining extractions above 95% at [HCl] = 4 M, P = 0.34 MPa and T = 40 °C. The extraction increased depending on the concentration of HCl. Eh–pH diagrams for Ag–Cl–H2O, Au–Cl–H2O and Pt–Cl–H2O were constructed to know the possible species in the solution. Full article
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14 pages, 1146 KiB  
Article
Recovery of Platinum from a Spent Automotive Catalyst through Chloride Leaching and Solvent Extraction
Recycling 2021, 6(2), 27; https://doi.org/10.3390/recycling6020027 - 17 Apr 2021
Cited by 8 | Viewed by 4001
Abstract
Considering economics and environmental sustainability, recycling of critical metals from end-of-life devices should be a priority. In this work the hydrometallurgical treatment of a spent automotive catalytic converter (SACC) using HCl with CaCl2 as a leaching medium, and solvent extraction (SX) with [...] Read more.
Considering economics and environmental sustainability, recycling of critical metals from end-of-life devices should be a priority. In this work the hydrometallurgical treatment of a spent automotive catalytic converter (SACC) using HCl with CaCl2 as a leaching medium, and solvent extraction (SX) with a thiodiglycolamide derivative, is reported. The aim was to develop a leaching scheme allowing high Pt recoveries and minimizing Al dissolution, facilitating the application of SX. The replacement of part of HCl by CaCl2 in the leaching step is viable, without compromising Pt recovery (in the range 75–85%), as found for the mixture 2 M CaCl2 + 8 M HCl when compared to 11.6 M HCl. All leaching media showed good potential to recover Ce, particularly for higher reaction times and temperatures. Regarding SX, results achieved with a model solution were promising, but SX for Pt separation from the real SACC solution did not work as expected. For the adopted experimental conditions, the tested thiodiglycolamide derivative in toluene revealed a very good loading performance for both Pt and Fe, but Fe removal and Pt stripping from the organic phases after contact with the SACC solution were not successfully accomplished. Hence, the reutilization of the organic solvent needs improvement. Full article
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9 pages, 707 KiB  
Article
Determination of Metals’ Content in Components Mounted on Printed Circuit Boards from End-of-Life Mobile Phones
Recycling 2020, 5(3), 20; https://doi.org/10.3390/recycling5030020 - 09 Sep 2020
Cited by 9 | Viewed by 4607
Abstract
The electronic components mounted on the printed circuit boards (PCBs) of mobile phones represent a resource that is rich in metals, and after separation from the boards, these components could be considered secondary raw materials. The concentrations of the valuable metals are insignificant [...] Read more.
The electronic components mounted on the printed circuit boards (PCBs) of mobile phones represent a resource that is rich in metals, and after separation from the boards, these components could be considered secondary raw materials. The concentrations of the valuable metals are insignificant when compared with those of complete PCBs; however, they could be significantly higher in a fraction formed from the separated components. This study focused on the analysis of Ag, Au, Cu, Nd, Nb, Ni, Pb, Pd, Sn, and Ta in fractions produced by the separation of all the components mounted on PCBs from several types of mobile phones. Atomic absorption spectrometry, atomic emission spectrometry, and mass spectrometry techniques were utilized, and a comparison of five older models of “brick” phones and five modern smartphones was conducted. Additionally, 50 kg of PCBs from the current recycling market were analyzed in the same way to create a summary of the current recycling stream. Full article
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Review

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20 pages, 1804 KiB  
Review
Highlighting the Role of Archaea in Urban Mine Waste Exploitation and Valorisation
Recycling 2023, 8(1), 20; https://doi.org/10.3390/recycling8010020 - 04 Feb 2023
Cited by 2 | Viewed by 3394
Abstract
E-materials become e-waste once they have been discarded without the intent of reuse. Due to its rich content of metals, among which many are Critical Raw Materials (CRMs), e-waste can be considered an urban mine to exploit and valorise. Common metal refining is [...] Read more.
E-materials become e-waste once they have been discarded without the intent of reuse. Due to its rich content of metals, among which many are Critical Raw Materials (CRMs), e-waste can be considered an urban mine to exploit and valorise. Common metal refining is performed by energy-intensive processes frequently based on the use of fossil fuel. Bio-metallurgy is a promising alternative for e-waste valorisation based on biological routes of specialised microorganisms able to leach solid-containing metals. Because of the physiology of these microorganisms, microbial leaching can be economically feasible, besides being an environmentally sustainable process. Like Bacteria and Fungi, Archaea are also capable of metal leaching activity, though their potential is underestimated. Among them, the extremophiles are the most studied and applied in the field of metal recovery, while mesophilic species are less common but still of high interest. Here we provide the state of industrial application of bio-metallurgy and report on the state of the art of Archaea exploitation in metal recovery from e-waste. Moreover, we give a special highlight to methanogenic archaea, which are able to convert CO2 into methane in order to highlight the potential for the valorisation of CO2-rich industrial streams generated by key processes (i.e., anaerobic digestion, concrete, and steel production) in CH4 for gas grid distribution, while making metals content in e-waste available again as raw material. Full article
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15 pages, 722 KiB  
Review
Biohydrometallurgical Recovery of Metals from Waste Electronic Equipment: Current Status and Proposed Process
Recycling 2022, 7(5), 67; https://doi.org/10.3390/recycling7050067 - 12 Sep 2022
Cited by 12 | Viewed by 4170
Abstract
Electronic waste (e-waste) is an emerging health and environmental burden due to the toxic substances present within e-wastes. To address this burden, e-wastes contain various base, rare earth and noble metals, which can be recovered from these substances, thus serving as secondary sources [...] Read more.
Electronic waste (e-waste) is an emerging health and environmental burden due to the toxic substances present within e-wastes. To address this burden, e-wastes contain various base, rare earth and noble metals, which can be recovered from these substances, thus serving as secondary sources of metals. Pyrometallurgical and hydrometallurgical processes have been developed to extract metals from e-waste. However, these techniques are energy-intensive and produce secondary wastes, which will add to the operating costs of the process. However, the biohydrometallurgical approach has been deemed as an eco-friendly, cost-effective, and environmentally friendly process that does not produce large quantities of secondary waste. However, research has focused chiefly on one-stage bioprocesses to recover the metals of interest and majorly on base metals recovery. Hence, this review proposes a two-stage bio-hydrometallurgical process where the first stage will consist of acidophilic iron and sulphur oxidising organisms to extract base metals, followed by the second stage which will consist of cyanide-producing organisms for the solubilisation of rare earth and precious metals. The solid waste residue that is produced from the system can be used in the synthesis of silica nanomaterials, which can be utilised for various applications. Full article
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28 pages, 4120 KiB  
Review
Electrochemical Approaches for the Recovery of Metals from Electronic Waste: A Critical Review
Recycling 2021, 6(3), 53; https://doi.org/10.3390/recycling6030053 - 09 Aug 2021
Cited by 44 | Viewed by 12226
Abstract
Electronic waste (e-waste) management and recycling are gaining significant attention due to the presence of precious, critical, or strategic metals combined with the associated environmental burden of recovering metals from natural mines. Metal recovery from e-waste is being prioritized in metallurgical extraction owing [...] Read more.
Electronic waste (e-waste) management and recycling are gaining significant attention due to the presence of precious, critical, or strategic metals combined with the associated environmental burden of recovering metals from natural mines. Metal recovery from e-waste is being prioritized in metallurgical extraction owing to the fast depletion of natural mineral ores and the limited geographical availability of critical and/or strategic metals. Following collection, sorting, and physical pre-treatment of e-waste, electrochemical processes-based metal recovery involves leaching metals in an ionic form in a suitable electrolyte. Electrochemical metal recovery from e-waste uses much less solvent (minimal reagent) and shows convenient and precise control, reduced energy consumption, and low environmental impact. This critical review article covers recent progress in such electrochemical metal recovery from e-waste, emphasizing the comparative significance of electrochemical methods over other methods in the context of an industrial perspective. Full article
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32 pages, 1339 KiB  
Review
Extraction of Valuable Elements from Red Mud with a Focus on Using Liquid Media—A Review
Recycling 2021, 6(2), 38; https://doi.org/10.3390/recycling6020038 - 10 Jun 2021
Cited by 40 | Viewed by 7397
Abstract
Bauxite residue, known as red mud, is a by-product of alumina production using the Bayer process. Currently, its total global storage amounts to over 4.6 billion tons, including about 600 million tons in Russia. The total global storage of red mud occupies large [...] Read more.
Bauxite residue, known as red mud, is a by-product of alumina production using the Bayer process. Currently, its total global storage amounts to over 4.6 billion tons, including about 600 million tons in Russia. The total global storage of red mud occupies large areas, leading to environmental damage and increasing environmental risks. Moreover, it contains a significant amount of sodium, which is easily soluble in subsoil water; therefore, a sustainable approach for comprehensive recycling of red mud is necessary. The bauxite residue contains valuable elements, such as aluminum, titanium, and scandium, which can be recovered using liquid media. In recent years, many methods of recovery of these elements from this waste have been proposed. This paper provides a critical review of hydrometallurgical, solvometallurgical, and complex methods for the recovery of valuable components from red mud, namely, aluminum, titanium, sodium, and rare and rare-earth elements. These methods include leaching using alkaline or acid solutions, ionic liquids, and biological organisms, in addition to red mud leaching solutions by extraction and sorption methods. Advantages and disadvantages of these processes in terms of their environmental impact are discussed. Full article
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