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Metals
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Extraction and Recycling of Refractory, Platinum Group Metals and Rare...
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Extraction and Recycling of Refractory, Platinum Group Metals and Rare Earth Elements

A special issue of Metals (ISSN 2075-4701). This special issue belongs to the section "Extractive Metallurgy".

Deadline for manuscript submissions: closed (20 March 2019) | Viewed by 24505

Special Issue Editor

Prof. Teodora Retegan

E-Mail Website
Guest Editor
Nuclear Chemistry and Industrial Materials Recycling, Chemistry and Chemical Engineering, Chalmers University of Technology, Kemivägen 4, vån.6, SE-41296 Göteborg, Sweden
Interests: hydrometallurgy; nuclear chemistry; recycling; recovery; metals; extraction

Special Issue Information

Dear Colleagues,

Extraction and recycling of metals have been around for millennia, and the development of the methodologies and chemistries have been tremendous in the last few decades.

We are looking forward to highlighting, in this Special Issue, the advancements made in the extraction and recycling of refractory, platinum group metals, and rare earth elements. Your research has to be novel, innovative and show potential for implementation, in a scholarly manner.

I would quote: “Waste is what is left when imagination fails.” but also do not forget that the primary extraction of metals requires an even higher dose of imagination, for a higher purity and better streams, and maybe to decrease the waste.

I am looking forward to receiving your contributions.

Prof. Teodora Retegan
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. Metals 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 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

  • Extraction
  • Recycling
  • Refractory metals
  • Platinum group metals
  • Rare earth elements
  • Hydrometallurgy
  • Pyrometallurgy
  • Ionic liquids
  • Supercritical fluids extraction
  • Secondary waste

Published Papers (5 papers)

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Research

15 pages, 3457 KiB  
Article
Extraction of Rare Earth Elements from Chloride Media with Tetrabutyl Diglycolamide in 1-Octanol Modified Carbon Dioxide
by Mary Case, Robert Fox, Donna Baek and Chien Wai
Metals 2019, 9(4), 429; https://doi.org/10.3390/met9040429 - 10 Apr 2019
Cited by 7 | Viewed by 3327
Abstract
Rare earth elements (REEs) are critical to our modern world. Recycling REEs from used products could help with potential supply issues. Extracting REEs from chloride media with tetrabutyl diglycolamide (TBDGA) in carbon dioxide could help recycle REEs with less waste than traditional solvents. [...] Read more.
Rare earth elements (REEs) are critical to our modern world. Recycling REEs from used products could help with potential supply issues. Extracting REEs from chloride media with tetrabutyl diglycolamide (TBDGA) in carbon dioxide could help recycle REEs with less waste than traditional solvents. Carbon dioxide as a solvent is inexpensive, inert, and reusable. Conditions for extraction of Eu from aqueous chloride media were optimized by varying moles percent of 1-octanol modifier, temperature, pressure, Eu concentration, TBDGA concentration, Cl− concentration, and HCl concentration. These optimized conditions were tested on a Y, Ce, Eu, Tb simulant material, REEs containing NdFeB magnets, and lighting phosphor material. The optimized conditions were found to be 23 °C, 24.1 MPa, 0.5 mol% 1-octanol, with an excess of TBDGA. At these conditions 95 ± 2% Eu was extracted from 8 M (mol/m3) HCl. Extraction from the mixed REE simulate material resulted in separation of Y, Eu, and Tb from the Ce which remained in the aqueous solution. The extraction on NdFeB magnet dissolved into 8 M HCl resulted in extraction of Pr, Nd, Dy, and Fe >97%. This results in a separation from B, Al, and Ni. Extraction from a trichromatic lighting phosphor leachate resulted in extraction of Y and Eu >93% and no extraction of Ba, Mg, and Al. Full article
(This article belongs to the Special Issue Extraction and Recycling of Refractory, Platinum Group Metals and Rare Earth Elements)
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11 pages, 3132 KiB  
Article
Hydrometallurgical Process for Zinc Recovery from C.Z.O. Generated by the Steelmaking Industry with Ammonia–Ammonium Chloride Solution
by Shenghai Yang, Duoqiang Zhao, Yafei Jie, Chaobo Tang, Jing He and Yongming Chen
Metals 2019, 9(1), 83; https://doi.org/10.3390/met9010083 - 14 Jan 2019
Cited by 12 | Viewed by 5599
Abstract
In this research, some experimental steps were investigated to recover zinc contained in crude zinc oxide (C.Z.O.). In the first stage, the C.Z.O. was treated in NH3–NH4Cl–H2O solution to dissolve the metals. The optimized leaching conditions in [...] Read more.
In this research, some experimental steps were investigated to recover zinc contained in crude zinc oxide (C.Z.O.). In the first stage, the C.Z.O. was treated in NH3–NH4Cl–H2O solution to dissolve the metals. The optimized leaching conditions in batch experiments were obtained: agitation speed 250 rpm, concentration of ammonia and ammonium chloride 2.5 mol/L and 5 mol/L, respectively, time 30min, temperature 40 °C, and L/S = 6 mL/g. The extraction percentage of zinc was over 81% under the optimized leaching conditions. The kinetic study indicates that zinc extraction from the C.Z.O particles was very rapid. In the second stage, the solution from the leaching process was purified by adding zinc dust to the solution. The Cu, Cd, Pb, Sb, and As could be reduced to levels of 0.03, 0.09, 0.87, 0.22, and 0.12 mg/L after the purification process. Finally, the electrowinning process was used to recover dissolved Zn from the final solution. The zinc content in the electrowon zinc was more than 99.99%. Full article
(This article belongs to the Special Issue Extraction and Recycling of Refractory, Platinum Group Metals and Rare Earth Elements)
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12 pages, 3944 KiB  
Article
Phase and Morphology Transformations in Sulfur-Fixing and Reduction Roasting of Antimony Sulfide
by Zhen Ouyang, Longgang Ye, Chaobo Tang and Yifeng Chen
Metals 2019, 9(1), 79; https://doi.org/10.3390/met9010079 - 14 Jan 2019
Cited by 4 | Viewed by 2777
Abstract
Metallurgical extraction of antimony (Sb) currently has the limitations of high energy consumption and adverse environmental impact. In this study, we proposed a cleaning process to extract Sb by metallurgy and beneficiation based on S-fixing and reduction roasting of Sb2S3 [...] Read more.
Metallurgical extraction of antimony (Sb) currently has the limitations of high energy consumption and adverse environmental impact. In this study, we proposed a cleaning process to extract Sb by metallurgy and beneficiation based on S-fixing and reduction roasting of Sb2S3. Metallic Sb can be obtained directly by using zinc oxide (ZnO) and carbon as sulfur-fixing and reducing agents, respectively, at 600–1000 °C, wherein S is fixed in the form of ZnS. The thermodynamic feasibility of the process of roasting and the effects of a range of process parameters on Sb generation were investigated comprehensively. The optimum conditions for metallic Sb generation were determined to be as follows: temperature of 800 °C, C powder size of 100–150 mesh, ZnO content of 1.1 times its stoichiometric requirement (α), and reaction time of 2 h. Under the optimum conditions, the proportion of Sb distributed in the metal phase reached 90.44% and the S-fixing rate reached 94.86%. The phase transformation of Sb progressed as follows: Sb2S3→Sb2O3→Sb. The Sb particle had mainly spherical and hexahedral morphologies after quenching and furnace cooling, and bonded little with ZnS. This research is potentially beneficial for the further design process of Sb powder and ZnS recovery by mineral separation. Full article
(This article belongs to the Special Issue Extraction and Recycling of Refractory, Platinum Group Metals and Rare Earth Elements)
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17 pages, 2390 KiB  
Article
Sustainable Hydrometallurgical Recovery of Valuable Elements from Spent Nickel–Metal Hydride HEV Batteries
by Kivanc Korkmaz, Mahmood Alemrajabi, Åke C. Rasmuson and Kerstin M. Forsberg
Metals 2018, 8(12), 1062; https://doi.org/10.3390/met8121062 - 14 Dec 2018
Cited by 22 | Viewed by 4111
Abstract
In the present study, the recovery of valuable metals from a Panasonic Prismatic Module 6.5 Ah NiMH 7.2 V plastic casing hybrid electric vehicle (HEV) battery has been investigated, processing the anode and cathode electrodes separately. The study focuses on the recovery of [...] Read more.
In the present study, the recovery of valuable metals from a Panasonic Prismatic Module 6.5 Ah NiMH 7.2 V plastic casing hybrid electric vehicle (HEV) battery has been investigated, processing the anode and cathode electrodes separately. The study focuses on the recovery of the most valuable compounds, i.e., nickel, cobalt and rare earth elements (REE). Most of the REE (La, Ce, Nd, Pr and Y) were found in the anode active material (33% by mass), whereas only a small amount of Y was found in the cathode material. The electrodes were leached in sulfuric acid and in hydrochloric acid, respectively, under different conditions. The results indicated that the dissolution kinetics of nickel could be slow as a result of slow dissolution kinetics of nickel oxide. At leaching in sulfuric acid, light rare earths were found to reprecipitate increasingly with increasing temperature and sulfuric acid concentration. Following the leaching, the separation of REE from the sulfuric acid leach liquor by precipitation as NaREE (SO4)2·H2O and from the hydrochloric acid leach solution as REE2(C2O4)3·xH2O were investigated. By adding sodium ions, the REE could be precipitated as NaREE (SO4)2·H2O with little loss of Co and Ni. By using a stoichiometric oxalic acid excess of 300%, the REE could be precipitated as oxalates while avoiding nickel and cobalt co-precipitation. By using nanofiltration it was possible to recover hydrochloric acid after leaching the anode material. Full article
(This article belongs to the Special Issue Extraction and Recycling of Refractory, Platinum Group Metals and Rare Earth Elements)
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17 pages, 4646 KiB  
Article
Leaching and Recovery of Rare-Earth Elements from Neodymium Magnet Waste Using Organic Acids
by Marino Gergoric, Christophe Ravaux, Britt-Marie Steenari, Fredrik Espegren and Teodora Retegan
Metals 2018, 8(9), 721; https://doi.org/10.3390/met8090721 - 13 Sep 2018
Cited by 50 | Viewed by 8228
Abstract
Over the last decade, rare-earth elements (REEs) have become critical in the European Union (EU) in terms of supply risk, and they remain critical to this day. End-of-life electronic scrap (e-scrap) recycling can provide a partial solution to the supply of REEs in [...] Read more.
Over the last decade, rare-earth elements (REEs) have become critical in the European Union (EU) in terms of supply risk, and they remain critical to this day. End-of-life electronic scrap (e-scrap) recycling can provide a partial solution to the supply of REEs in the EU. One such product is end-of-life neodymium (NdFeB) magnets, which can be a feasible source of Nd, Dy, and Pr. REEs are normally leached out of NdFeB magnet waste using strong mineral acids, which can have an adverse impact on the environment in case of accidental release. Organic acids can be a solution to this problem due to easier handling, degradability, and less poisonous gas evolution during leaching. However, the literature on leaching NdFeB magnets waste with organic acids is very scarce and poorly investigated. This paper investigates the recovery of Nd, Pr, and Dy from NdFeB magnets waste powder using leaching and solvent extraction. The goal was to determine potential selectivity between the recovery of REEs and other impurities in the material. Citric acid and acetic acid were used as leaching agents, while di-(2-ethylhexyl) phosphoric acid (D2EHPA) was used for preliminary solvent extraction tests. The highest leaching efficiencies were achieved with 1 mol/L citric acid (where almost 100% of the REEs were leached after 24 h) and 1 mol/L acetic acid (where >95% of the REEs were leached). Fe and Co—two major impurities—were co-leached into the solution, and no leaching selectivity was achieved between the impurities and the REEs. The solvent extraction experiments with D2EHPA in Solvent 70 on 1 mol/L leachates of both acetic acid and citric acid showed much higher affinity for Nd than Fe, with better extraction properties observed in acetic acid leachate. The results showed that acetic acid and citric acid are feasible for the recovery of REEs out of NdFeB waste under certain conditions. Full article
(This article belongs to the Special Issue Extraction and Recycling of Refractory, Platinum Group Metals and Rare Earth Elements)
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