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Minerals
Special Issues
Green and Efficient Recovery/Extraction of Rare Earth Resources
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Green and Efficient Recovery/Extraction of Rare Earth Resources

A special issue of Minerals (ISSN 2075-163X). This special issue belongs to the section "Mineral Processing and Extractive Metallurgy".

Deadline for manuscript submissions: 31 July 2024 | Viewed by 3191

Special Issue Editors

Dr. Gaofeng Wang

E-Mail Website
Guest Editor
Guangzhou Institute of Geochemistry, Chinese Academy of Sciences, Guangzhou 510640, China
Interests: clay mineral; mining; rare earth elements; ion-adsorption rare earth deposits; electrokinetics; adsorption; surfaces and interfaces
Dr. Yongqiang Yang

E-Mail Website
Guest Editor
Guangzhou Institute of Geochemistry, Chinese Academy of Sciences, Guangzhou 510640, China
Interests: environmental geochemistry; water pollution control; biological nitrogen removal; rare earth mining tailings; wastewater treatment

Special Issue Information

Dear Colleagues,

Rare earth elements (REEs) are critical and strategic components for the development of future green and low-carbon economies due to their fundamental roles in many clean and renewable energy technologies (e.g., solar panels, wind turbines, and hybrid vehicle batteries). At present, the global demand for REEs is continuously increasing. Nevertheless, the worldwide supply of REEs is limited, and mining REEs from natural resources has a low recovery rate and causes many environmental problems. Therefore, developing innovative methods for the green and efficient recovery of REEs is a key strategy for meeting the global increasing demand for REEs.

REEs are predominantly mined from mineral phase-type ores (e.g., the Bayan Obo rare earth ores) and ion-adsorption-type rare earth deposits (e.g., weathering crust). Due to their exhaustive exploitation, the natural repository for REEs is decreasing dramatically. Recovering REEs from secondary resources, such as fly ash, mine tailing, and electronic waste, is an alternative method of extraction.

This Special Issue is organized into three sections:

Section 1: Recovery/Mining of REEs from ion-adsorption rare earth deposits: Methods and case studies.
Section 2: Recovery/Extraction/Hydrometallurgy of REEs from mineral phase rare earth ores: Methods and case studies.
Section 3: Recovery/Extraction of REEs from secondary resources: Methods and case studies.

This Special Issue aims to discuss all methods for recovering REEs from various REE-carriers, including weathering crust, minerals, and secondary resources. All types of experimental, theoretical, and simulation studies are welcome.

Dr. Gaofeng Wang
Dr. Yongqiang Yang
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. Minerals 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

  • rare earth elements
  • recovery
  • extraction
  • mining

Published Papers (5 papers)

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Research

15 pages, 1290 KiB  
Article
Microstructure Evolution Law of Ionic Rare Earth at Different Depths in In Situ Leaching Mine Site
by Zhongqun Guo, Haoxuan Wang, Qiqi Liu, Feiyue Luo and Yanshuo Liu
Minerals 2024, 14(6), 570; https://doi.org/10.3390/min14060570 - 29 May 2024
Viewed by 190
Abstract
Due to the inhomogeneity and anisotropy of mine rock bodies, ionic rare earth ore bodies exhibit varying pore structures at different depths. This research focuses on an ionic rare earth mine in Fujian Province, where in situ ore samples rather than remodeled soil [...] Read more.
Due to the inhomogeneity and anisotropy of mine rock bodies, ionic rare earth ore bodies exhibit varying pore structures at different depths. This research focuses on an ionic rare earth mine in Fujian Province, where in situ ore samples rather than remodeled soil samples were studied. Samples from the fully weathered layer at depths of 1 m, 12 m, and 21 m, both before and after leaching, were collected for onsite analysis. Microscopic pore characteristics were evaluated using scanning electron microscopy, and digital image processing was utilized to study the evolution of the pore scale, distribution, and shape in rare earth ore samples at various depths pre- and post-leaching. The results indicate an increase in the ore body’s porosity with the depth of the ore samples both before and after leaching. The variation in pore scale is predominantly dictated by the ratio of macropore and large pores. Pre-leaching, the middle ore sample showcased the highest uniformity, with the upper part being the most irregular. Post-leaching, the highest uniformity was observed in the lower ore samples, with the upper part remaining irregular. Pre-leaching, as depth increased, the pore distribution in ore samples became more dispersed, with decreasing orderliness. Post-leaching, the orderliness was most improved in upper ore samples, while middle ore samples became the least orderly. Additionally, before leaching, pore-shape roughness increased with depth; after leaching, the pore shape became more rounded as depth increased, simplifying the pore-shape structure of the ore samples both before and after leaching. Full article
(This article belongs to the Special Issue Green and Efficient Recovery/Extraction of Rare Earth Resources)
14 pages, 3982 KiB  
Article
Removal of Low Concentrations of Er(III) from Water Using Heptadecyl-1,1-bisphosphonic Acid
by Chunhua Bai, Xiaoning Yang and Guanghui Li
Minerals 2024, 14(6), 534; https://doi.org/10.3390/min14060534 - 22 May 2024
Viewed by 232
Abstract
The removal of low concentrations of rare-earth ions (e.g., Er(III)) from water has stimulated interest in the field of mineral processing and water treatment. Here, an ion-exchange and complexation-assisted precipitation method for the removal of low concentrations of Er(III) from water using heptadecyl-1,1-bisphosphonic [...] Read more.
The removal of low concentrations of rare-earth ions (e.g., Er(III)) from water has stimulated interest in the field of mineral processing and water treatment. Here, an ion-exchange and complexation-assisted precipitation method for the removal of low concentrations of Er(III) from water using heptadecyl-1,1-bisphosphonic acid (HBPA) was investigated. The results showed that effective cation-exchange between Er(III) ions and the bisphosphonate headgroup was achieved, and the solution pH abruptly decreased from 6.5 to around 3.1 at the first stage, which further led to the formation of less soluble Er(III) heptadecyl-1,1-bisphosphonate complexes. While low concentrations of Er(III) ions in water are typically treated by the addition of HBPA, followed by the addition of sodium bicarbonate (adjusting the pH to 6–8) and activate carbon, Er(III) ions could be efficiently removed from aqueous solution after about 30 min based on the cation-exchange and complexation-assisted precipitation method. Additionally, the removal of ultra trace amounts of Er(III) ions was not significantly affected by coexisting trace amounts of alkaline-earth metal ions (Mg2+, Ca2+ and Sr2+). HBPA is an effective Er(III) chelator, which may be a potential and promising alternative technique to remove Er(III) ions from aqueous solutions. Full article
(This article belongs to the Special Issue Green and Efficient Recovery/Extraction of Rare Earth Resources)
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15 pages, 3821 KiB  
Article
Role of Calcium Chloride on the Eluting Process of Residual Ammonium from Weathered Crust Elution-Deposited Rare Earth Ore Tailings
by Jian Feng, Xiaoyan Wu, Fang Zhou and Ruan Chi
Minerals 2024, 14(5), 521; https://doi.org/10.3390/min14050521 - 17 May 2024
Viewed by 359
Abstract
A large amount of ammonium salt leaching agent will remain in the leaching site of weathered crust elution-deposited rare earth ore (WREOs). The release of residual ammonium (RA) will seriously affect the water system ecology of the mining area, and it is urgent [...] Read more.
A large amount of ammonium salt leaching agent will remain in the leaching site of weathered crust elution-deposited rare earth ore (WREOs). The release of residual ammonium (RA) will seriously affect the water system ecology of the mining area, and it is urgent to control it. In this paper, column eluting was used to simulate the eluting process of RA in rare earth (RE) ore tailings, and the effects of calcium chloride concentration, eluting temperature, liquid-solid ratio, eluent pH and eluent flow rate on the eluting process of RA in rare earth ore tailings were discussed. It was found that calcium chloride could effectively elute the RA from ore tailings. Eluting agent pH almost had no effect on the eluting process of RA in the pH range of 4–6, and a greater impact on it at pH 8. The flow rate could effectively enhance the elution efficiency. The optimum conditions were calcium ion concentration of 0.1 mol/L, liquid-solid ratio of 2:1, pH 4–6, flow rate of 0.6 mL/min and elution at room temperature. At this time, the elution efficiency of RA was 91.85%. The eluting process of RA in ore tailings was controlled by the inner particle diffusing according to the kinetic analysis. The reaction order was 0.368, and the activation energy of the reaction is 12.450 kJ/mol. This will provide a theoretical basis and technical support for the efficient eluting process of residual ammonium in the leaching site of WREOs. Full article
(This article belongs to the Special Issue Green and Efficient Recovery/Extraction of Rare Earth Resources)
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15 pages, 3045 KiB  
Article
Transport Model of Rare Earth Elements in Weathering Crusts during Electrokinetic Mining
by Gaofeng Wang, Bowen Ling, Xiaoliang Liang, Jie Xu, Shichang Kang, Jingming Wei, Wei Tan, Runliang Zhu, Jianxi Zhu and Hongping He
Minerals 2024, 14(4), 360; https://doi.org/10.3390/min14040360 - 29 Mar 2024
Viewed by 956
Abstract
Electrokinetic mining (EKM) is a novel method for rare earth element (REE) mining that can achieve green and efficient recovery of REEs. However, as yet, there is no accurate model for describing the electrokinetic transport of REEs in weathering crusts, and this hinders [...] Read more.
Electrokinetic mining (EKM) is a novel method for rare earth element (REE) mining that can achieve green and efficient recovery of REEs. However, as yet, there is no accurate model for describing the electrokinetic transport of REEs in weathering crusts, and this hinders the wider application of EKM. The conventional model fails to capture the microscale transport physics occurring in the nanochannels that exist ubiquitously in weathering crusts. Consequently, the existing models cannot distinguish the mobilities of different REEs. Here, we report a new model for a more faithful description of the electrokinetic transport of REEs in weathering crusts that considers the ionic size, which has previously been neglected. We reveal that the electrokinetic transport of heavy REEs (HREEs) is faster than that of light REEs (LREEs) in weathering crusts, which is contrary to the predictions of conventional models. Our model was validated experimentally by measurements of the electrokinetic transport of two LREEs (La and Sm) and an HREE (Er) in weathering crusts. The speed of electrokinetic transport follows the order Er > Sm > La. Our findings suggest that the ionic size is a non-negligible factor affecting the electrokinetic transport of REEs in weathering crusts containing nanochannels. This work offers a constitutive model to describe the electrokinetic transport of REEs in weathering crusts, which promotes both theoretical developments and practical applications of EKM. Full article
(This article belongs to the Special Issue Green and Efficient Recovery/Extraction of Rare Earth Resources)
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15 pages, 7941 KiB  
Article
An Environmentally Friendly Sulfuric Acid Decomposition Strategy for Mixed Rare Earth Concentrate
by Shaochun Hou, Bo Zhang, Wenjun Li, Tuo Zhao, Zongyang Da and Chenghong Liu
Minerals 2024, 14(2), 185; https://doi.org/10.3390/min14020185 - 9 Feb 2024
Viewed by 1021
Abstract
A novel environmentally friendly one-step decomposition strategy for mixed rare earth concentrate of Bayan Obo in sulfuric acid solution was proposed in this work. In this process, more than 84% of bastnasite and monazite were decomposed in the leaching step at a temperature [...] Read more.
A novel environmentally friendly one-step decomposition strategy for mixed rare earth concentrate of Bayan Obo in sulfuric acid solution was proposed in this work. In this process, more than 84% of bastnasite and monazite were decomposed in the leaching step at a temperature lower than the boiling point of sulfuric acid solution. So, the dilapidation of sulfuric acid in this current proposed process will be reduced to a large extent. The stability region of rare earth ion in the RE(La, Ce, Nd)-F-P-SO4-H2O system at 170 °C has been proven through Eh-pH diagrams. The factors influencing decomposition of rare earth concentrate in this process were also investigated and the optimal leaching conditions were determined to be a leaching temperature of 170 °C with an ore/acid ratio of 1:5 (g/mL), a sulfuric acid concentrate of 75% and a leaching time of 80 min. The mineralogical changes occurring during the H2SO4 leaching process were investigated by X-ray diffraction and SEM-EDS. The analysis results showed that bastnasite and most of monazite had been decomposed, leaving only a small amount of monazite in the leaching residue. Full article
(This article belongs to the Special Issue Green and Efficient Recovery/Extraction of Rare Earth Resources)
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Planned Papers

The below list represents only planned manuscripts. Some of these manuscripts have not been received by the Editorial Office yet. Papers submitted to MDPI journals are subject to peer-review.

1. Zhihong Tu et al.
2. Jie Xu et al.
3. Shichang Kang et al.
4. Guanghui Li et al.
5. Yongqiang Yang et al.
6. Gaofeng Wang et al.
7. Yingya Wang et al.
8. Lingbo Zhou et al.
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