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Recycling
Special Issues
Emerging Technologies in the Hydrometallurgical Recycling of Critical Metals
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Emerging Technologies in the Hydrometallurgical Recycling of Critical Metals

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

Deadline for manuscript submissions: 31 January 2025 | Viewed by 6194

Special Issue Editor

Dr. Ana Paula Paiva

E-Mail Website
Guest 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 concept of critical material was created by the related expert commissions of the European Union in 2011. Since then, the number of identified critical materials included in the lists published every three years has been increasing. Metals occupy a major part of those lists, since many hold significant importance for key sectors in the European economy, are hardly replaceable, and have highly threatened supply. It is crucial to invest in the creation and development of sustainable technologies to reuse and recycle metals from end-of-life devices, residues, gaseous and liquid effluents, wastes, and scraps to effectively establish a circular economy and protect the future of the planet and all living species.

In recent years, hydrometallurgy has been playing a key role in the sustainable recycling of metals from several secondary sources. Hence, an updated state of the art of emerging hydrometallurgical technologies collected in a Special Issue is of great value.

This Special Issue welcomes critical reviews, original research, and case study articles dealing with innovative and emerging hydrometallurgical trends to efficiently and selectively recycle metals from secondary sources. Fundamental and applied investigations on hydrometallurgical methodologies would be highly appreciated and may also include solvometallurgical and biological approaches.

Dr. Ana Paula Paiva
Guest Editor

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. Recycling 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 1800 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

  • secondary resources
  • critical metals
  • metals recycling
  • sustainable metals recovery
  • hydrometallurgy
  • solvometallurgy
  • bio-hydrometallurgy

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Published Papers (4 papers)

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Research

20 pages, 2959 KiB  
Article
A Hydrometallurgical Process for the Recovery of Noble Metals (Au, Pt, Ir, and Ta) from Pyrolyzed and Acid-Digested Solutions of Single-Use Medical Devices
by Angeliki Lampou, Evgenios Kokkinos, Charikleia Prochaska, Theodosios Tsiogkas, Effrosyni Peleka, Anthimos Xenidis and Anastasios Zouboulis
Recycling 2024, 9(6), 118; https://doi.org/10.3390/recycling9060118 - 5 Dec 2024
Viewed by 545
Abstract
Developing an efficient recycling route for spent single-use medical devices is essential for recovering precious metals. The proposed complete hydrometallurgical route goes through the initial pyrolysis and acid digestion steps, expanding upon our previous relevant work in the field, followed by solvent extraction, [...] Read more.
Developing an efficient recycling route for spent single-use medical devices is essential for recovering precious metals. The proposed complete hydrometallurgical route goes through the initial pyrolysis and acid digestion steps, expanding upon our previous relevant work in the field, followed by solvent extraction, stripping, and precipitation procedures. In this study, a complete hydrometallurgical process was developed for the recovery of gold, platinum, iridium, and tantalum, separating them from other metals, i.e., from iron, chromium, and nickel, also present in the examined medical devices, i.e., (i) diagnostic electrophysiology catheters, containing gold, (ii) diagnostic guide wires, containing platinum and iridium alloys, and (iii) self-expanding stents, containing tantalum. This study reports the experimental results of selecting an efficient extractant, stripping, and precipitation agent, along with the effects of key factors that influence each consecutive step of the process, i.e., agent concentration, aqueous to organic phase ratio, contact time, and pH, using simulated metal solutions and also applying the obtained optimal conditions to the treatment of real sample solutions. For the selective separation of gold, Aliquat 336 was used to extract it in the organic phase; it was then stripped using a thiourea solution and precipitated by utilizing an iron sulfate (II) solution and proper pH adjustment. The selective separation of platinum was achieved by using Aliquat 336 for the organic phase extraction and a perchlorate acid solution for stripping it back into the aqueous solution and adding a sodium bromate solution to precipitate it. Due to the similar chemical behavior, the selective recovery of iridium followed the same processes as that of platinum, and the separation between them was achieved through selective precipitation, as heating the solution and adjusting the pH value resulted in the selective precipitation of iridium. Lastly, the selective recovery of tantalum consists of extraction by using Alamine 336, then stripping it back to the aqueous phase by using sodium chloride, and precipitation by using potassium salt solution and proper pH adjustment. A total recovery of 88% for Au, 86% for Pt, 84% for Ir, and 80% for Ta was obtained, thus achieving a high uptake of precious metals from the examined real spent/waste samples. Full article
(This article belongs to the Special Issue Emerging Technologies in the Hydrometallurgical Recycling of Critical Metals)
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14 pages, 2135 KiB  
Article
Experimental Study on the Separation of Selected Metal Elements (Sm, Co, Fe, and Cu) from Nitric Acid Leachate Using Specific Precipitants
by Jian-Zhi Wang, Yi-Chin Tang and Yun-Hwei Shen
Recycling 2024, 9(6), 111; https://doi.org/10.3390/recycling9060111 - 14 Nov 2024
Viewed by 599
Abstract
As more countries emphasize the importance of the circular economy, recycling resources from waste has become increasingly crucial. This study proposes a novel separation process for SmCo magnets, which can separate and recover metals by precipitation, thus reducing the amount of solvent used. [...] Read more.
As more countries emphasize the importance of the circular economy, recycling resources from waste has become increasingly crucial. This study proposes a novel separation process for SmCo magnets, which can separate and recover metals by precipitation, thus reducing the amount of solvent used. The precipitation process involved the use of Na2SO4, NH4OH, and H2C2O4 to separate Sm, Fe, Cu, and Co, resulting in high precipitation efficiencies of 96.11%, 99.97%, 93.81%, and 98.15%, respectively. Moreover, the recovered metals can be directly used to create magnets after calcination, making this process a step towards achieving a circular economy. Full article
(This article belongs to the Special Issue Emerging Technologies in the Hydrometallurgical Recycling of Critical Metals)
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9 pages, 1387 KiB  
Article
Selective Recovery of Tin from Electronic Waste Materials Completed with Carbothermic Reduction of Tin (IV) Oxide with Sodium Sulfite
by Wojciech Hyk and Konrad Kitka
Recycling 2024, 9(4), 54; https://doi.org/10.3390/recycling9040054 - 26 Jun 2024
Viewed by 2085
Abstract
A new approach for the thermal reduction of tin dioxide (SnO2) in the carbon/sodium sulfite (Na2SO3) system is demonstrated. The process of tin smelting was experimentally optimized by adjusting the smelting temperature and amounts of the chemical [...] Read more.
A new approach for the thermal reduction of tin dioxide (SnO2) in the carbon/sodium sulfite (Na2SO3) system is demonstrated. The process of tin smelting was experimentally optimized by adjusting the smelting temperature and amounts of the chemical components used for the thermal reduction of SnO2. The numbers obtained are consistent with the thermodynamic characteristics of the system and molar fractions of reactants derived from the proposed mechanism of the SnO2 thermal reduction process. They reveal that the maximum yield of tin is obtained if masses of C, Na2SO3 and SnO2 are approximately in the ratio 1:2:3 and the temperature is set to 1050 °C. The key role in the suggested mechanism is the thermal decomposition of Na2SO3. It was deduced from the available experimental data that the produced sulfur dioxide undergoes carbothermic reduction to carbonyl sulfide—an intermediate product involved in the bulk reduction of SnO2. Replacing sodium sulfite with sodium sulfate, sodium sulfide and even elemental sulfur practically terminated the production of metallic tin. The kinetic analysis was focused on the determination of the reaction orders for the two crucial reactants involved in the smelting process. Full article
(This article belongs to the Special Issue Emerging Technologies in the Hydrometallurgical Recycling of Critical Metals)
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15 pages, 4531 KiB  
Article
Recycling of Rhenium from Superalloys and Manganese from Spent Batteries to Produce Manganese(II) Perrhenate Dihydrate
by Katarzyna Leszczyńska-Sejda, Arkadiusz Palmowski, Michał Ochmański, Grzegorz Benke, Alicja Grzybek, Szymon Orda, Karolina Goc, Joanna Malarz and Dorota Kopyto
Recycling 2024, 9(3), 36; https://doi.org/10.3390/recycling9030036 - 30 Apr 2024
Cited by 1 | Viewed by 1889
Abstract
This work presents the research results on the development of an innovative, hydrometallurgical technology for the production of manganese(II) perrhenate dihydrate from recycled waste. These wastes are scraps of Ni-based superalloys containing Re and scraps of Li–ion batteries containing Mn—specifically, solutions from the [...] Read more.
This work presents the research results on the development of an innovative, hydrometallurgical technology for the production of manganese(II) perrhenate dihydrate from recycled waste. These wastes are scraps of Ni-based superalloys containing Re and scraps of Li–ion batteries containing Mn—specifically, solutions from the leaching of black mass. This work presents the conditions for the production of Mn(ReO4)2·2H2O. Thus, to obtain Mn(ReO4)2·2H2O, manganese(II) oxide was used, precipitated from the solutions obtained after the leaching of black mass from Li–ion batteries scrap and purified from Cu, Fe and Al (pH = 5.2). MnO2 precipitation was carried out at a temperature < 50 °C for 30 min using a stoichiometric amount of KMnO4 in the presence of H2O2. MnO2 precipitated in this way was purified using a 20% H2SO4 solution and then H2O. Purified MnO2 was then added alternately with a 30% H2O2 solution to an aqueous HReO4 solution. The reaction was conducted at room temperature for 30 min to obtain a pH of 6–7. Mn(ReO4)2·2H2O precipitated by evaporating the solution to dryness was purified by recrystallization from H2O with the addition of H2O2 at least twice. Purified Mn(ReO4)2·2H2O was dried at a temperature of 100–110 °C. Using the described procedure, Mn(ReO4)2·2H2O was obtained with a purity of >99.0%. This technology is an example of the green transformation method, taking into account the 6R principles. Full article
(This article belongs to the Special Issue Emerging Technologies in the Hydrometallurgical Recycling of Critical Metals)
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