Recent Developments on the Leaching Process of Rare Earth Ore

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

Deadline for manuscript submissions: closed (30 November 2023) | Viewed by 11669

Special Issue Editors

Key Laboratory for Green Chemical Process of Ministry of Education, Wuhan Institute of Technology, Wuhan 430073, China
Interests: leaching; rare earth ore
School of Chemistry and Environmental Engineering, Key Laboratory of Green Chemical Process of Ministry of Education, Engineering Research Center of Phosphorus Resources Development and Utilization of Ministry of Education, Hubei Key Laboratory of Novel Reactor and Green Chemical Technology, Wuhan Institute of Technology, Wuhan 430205, China
Interests: separation and purification of rare earth elements; molecular simulation of the separation process

Special Issue Information

Dear Colleagues,

Rare earth elements (REEs), also known as “industrial vitamins”, are of immense importance. They are widely used in the production of magnets, alloys, catalysts, batteries, medical equipment and superconductors, etc. REEs are made up of 17 elements including lanthanide elements (La, Ce, Pr, Nd Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu); scandium (Sc); and yttrium (Y), which are generally divided into three categories—except Sc and Pm—on the basis of the solubility of rare earth sulfate: light rare earth elements (LREEs) (La, Ce, Pr, Nd); middle rare earth elements (MREEs) (Sm, Eu, Gd, Tb, Dy); and heavy rare earth elements (HREEs) (Ho, Er, Tm, Yb, Lu, Y ).

REEs can derive from different kinds of minerals, including monazite, bastnaesite and weathered crust elution-deposited rare earth ores (WREO). However, more attention must be paid to the exploitation of WREO, due to the rich MREEs and HREEs that account for over 80% of the world’s known resources. WREO can be processed by the chemical leaching method. This method employs ammonium salt as the leaching agent due to its special characteristic of REEs that are present in clay minerals as adsorbed ions. At present, in situ leaching as a mature leaching technology is applied in the actual mine production.

This Special Issue aims to provide helpful theoretical guidance and technical support for green leaching and the process intensification of WREO.

Prof. Dr. Fang Zhou
Dr. Yuefei Zhang
Guest Editors

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Keywords

  • rare earth
  • rare earth ore
  • leaching
  • swelling
  • seepage

Published Papers (9 papers)

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Research

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15 pages, 3209 KiB  
Article
Distinct Extraction Behaviors of La/Ce and Sc/Y in the Phosphoric Acidic Leachate of Bauxite Residues and Their Sequential Extraction with Di-(2-Ethylhexyl) Phosphoric Acid as Extractant
by Bowen Li, Bona Deng, Yuqi Yao, Chuanli Wang, Yaoyang Ruan, Fang Zhou, Ru’an Chi and Hanquan Zhang
Minerals 2023, 13(10), 1345; https://doi.org/10.3390/min13101345 - 22 Oct 2023
Viewed by 744
Abstract
Bauxite residue is a hazardous solid waste produced in the alumina production process and has also become a significant rare earth resource. The extraction behaviors of La, Ce, Sc and Y solubilized in the phosphoric acidic leachate of bauxite residue were investigated in [...] Read more.
Bauxite residue is a hazardous solid waste produced in the alumina production process and has also become a significant rare earth resource. The extraction behaviors of La, Ce, Sc and Y solubilized in the phosphoric acidic leachate of bauxite residue were investigated in this study with di-(2-ethylhexyl) phosphoric acid as the extractant. With a relatively low concentration of 2% at an aqueous solution pH of 1.5, 90% Sc and 98% Y were extracted by di-(2-ethylhexyl) phosphoric acid. Less than 5% La and Ce and impurities of Fe, Al, Ti and Ca were extracted in this situation. As the concentration of di-(2-ethylhexyl) phosphoric acid increased to 20%, almost all the Sc and Y were extracted and the extraction ratios of La and Ce were 87% and 95%, respectively. A good separation of REEs against impurities was simultaneously obtained in the solvent extraction process and their separation coefficients were much higher than 1. A stepwise extraction process was proposed and established to extract Sc/Y and La/Ce sequentially from the phosphoric acidic leachate. It was further revealed that the Sc and Y in the acidic leachate were extracted by di-(2-ethylhexyl) phosphoric acid through an ion exchange process, and that the extraction of La and Ce was due to an antagonistic process where both an ion exchange reaction and a solvation reaction occurred. Full article
(This article belongs to the Special Issue Recent Developments on the Leaching Process of Rare Earth Ore)
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14 pages, 3176 KiB  
Article
Promotion Mechanism of Ammonium Formate in Ammonium Salt Leaching Process for Weathered Crust Elution-Deposited Rare Earth Ores
by Xing Gao, Yongwei Ma, Fang Zhou, Qutian Zhang, Dandan Zhang, Junxia Yu and Ruan Chi
Minerals 2023, 13(10), 1286; https://doi.org/10.3390/min13101286 - 30 Sep 2023
Viewed by 655
Abstract
Weathered crust elution-deposited rare earth ores (WREOs) are significant strategic mineral resources. In industry, in situ leaching technology is usually applied with ammonium chloride and ammonium sulfate as the leaching solution. However, the slow seepage velocity of the leaching solution and low rare [...] Read more.
Weathered crust elution-deposited rare earth ores (WREOs) are significant strategic mineral resources. In industry, in situ leaching technology is usually applied with ammonium chloride and ammonium sulfate as the leaching solution. However, the slow seepage velocity of the leaching solution and low rare earth leaching efficiency still need to be improved. Ammonium formate can effectively improve the WREO leaching process. In order to further explore the effects of ammonium formate on the ammonium salt leaching process for WREOs, ammonium chloride and ammonium sulfate compounded with ammonium formate were used as leaching agents to determine their effects on leaching efficiency, seepage velocity and swelling. The results show that in the presence of ammonium formate, the rare earth leaching efficiencies with ammonium chloride and ammonium sulfate are both slightly increased, the seepage velocity of ammonium chloride and ammonium sulfate is increased by 1.67 × 10−4 cm·s−1 and 1.18 × 10−4 cm·s−1, and the swelling percentage falls by 0.14% and 0.37%, respectively. The thickness of the adsorbed water layer and thermogravimetric and XRD results confirm that ammonium formate can inhibit surface hydration and thus improve the WREO leaching process. Full article
(This article belongs to the Special Issue Recent Developments on the Leaching Process of Rare Earth Ore)
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18 pages, 7055 KiB  
Article
Effect of Potassium Salt on Swelling of Halloysite Clay Mineral during Leaching Process of Ionic Rare Earth Ore
by Qi Hu, Yuanlai Xu, Xiangyi Deng, Shimin Hu, Jiaying Xu, Fang Zhou and Ru’an Chi
Minerals 2023, 13(7), 906; https://doi.org/10.3390/min13070906 - 04 Jul 2023
Cited by 1 | Viewed by 822
Abstract
Currently, the primary method for leaching rare earth ores is through in situ leaching. This approach involves contact between clay minerals and liquids, which can lead to the potential swelling of clay minerals with water, triggering natural disasters such as landslides. The main [...] Read more.
Currently, the primary method for leaching rare earth ores is through in situ leaching. This approach involves contact between clay minerals and liquids, which can lead to the potential swelling of clay minerals with water, triggering natural disasters such as landslides. The main purpose of this study is to select the suitable anti-swelling solution for Hunan Jianghua ionic rare earth ore. According to the ore composition analysis, 88 wt% of Hunan Jianghua ionic rare earth ore is composed of halloysite clay mineral. Therefore, halloysite clay mineral is used to investigate its anti-swelling behavior in order to provide a reference for future research on the selection of raw ore swelling inhibitors. In this study, the traditional leaching agent, MgSO4 solution, was used as the solvent along with two additional compounds, CH3COOK and KCl, which were prepared in different concentrations to form a new composite swelling inhibitor solution to observe their effect on the swelling rate of halloysite clay mineral. At the same time, the seepage velocity of halloysite clay mineral with different anti-swelling solutions is studied. The results indicate that the optimal concentration in the CH3COOK + MgSO4 solution system is 0.05 mol/dm3. At this concentration, the swelling rate is 5.129%, the inhibition rate is 20.08%, and the seepage velocity rate is 12.51 × 10−3 cm/min, respectively. In KCl + MgSO4 solution, the swelling rate is 4.868%, the inhibition rate is 24.15% and the seepage velocity rate is 13.23 × 10−3 cm/min at the concentration of 0.02 mol/dm3, which is the optimum concentration. In addition, FTIR and TG studies have further demonstrated the mechanism by which these two composite bulking inhibitors inhibit the swelling of halloysite clay mineral. Full article
(This article belongs to the Special Issue Recent Developments on the Leaching Process of Rare Earth Ore)
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13 pages, 2919 KiB  
Article
Influence of Leaching Solution on the Soil-Water Characteristics of Ion-Absorbed Rare Earth Minerals and Its Hysteresis Effect
by Zhong-qun Guo, Ling-feng Liu, Tao Tang, Ke-fan Zhou and Xiao-jun Wang
Minerals 2023, 13(5), 637; https://doi.org/10.3390/min13050637 - 03 May 2023
Viewed by 1188
Abstract
The soil-water characteristic curve is the basic constitutive relation to express the water-holding characteristics of ion-absorbed rare earth. The simulated solution mining test and pressure plate apparatus tests were carried out, the relationship between matric suction and water content under different leaching actions [...] Read more.
The soil-water characteristic curve is the basic constitutive relation to express the water-holding characteristics of ion-absorbed rare earth. The simulated solution mining test and pressure plate apparatus tests were carried out, the relationship between matric suction and water content under different leaching actions was obtained. Using the Fredlund and Xing four-parameter model, the soil-water characteristic curves of ion-absorbed rare earth under different leaching actions were obtained, and the changing trend of each parameter was analyzed, and the influence of different leaching methods on the water-holding characteristic of soil was obtained. For different types of leaching solutions, the water-holding capacity of the soil varies from strong to weak for pure water, the 3% magnesium sulfate solution, and the 3% ammonium sulfate solution; as the concentration of the leaching solution increases, the water-holding capacity of the sample gradually decreases, and it decreases most significantly from 0% to 2%. Moreover, the saliency of the “hysteresis effect” of the soil-water characteristic curve was from high to low for pure water, the 3% magnesium sulfate solution, and the 3% ammonium sulfate solution, and the “hysteresis effect” showed a decreasing trend with the increase in the concentration. Full article
(This article belongs to the Special Issue Recent Developments on the Leaching Process of Rare Earth Ore)
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14 pages, 2647 KiB  
Article
Evolutionary Law of Pore Structure of Ion-Adsorbed Rare Earth Ore Leaching Process
by Xiaoming Zhang, Zhongquan Gao, Yunzhang Rao, Liang Shi and Wei Xu
Minerals 2023, 13(3), 322; https://doi.org/10.3390/min13030322 - 24 Feb 2023
Cited by 4 | Viewed by 1330
Abstract
In the process of ion-adsorbed rare earth (RE) ore leaching and mining, the injected chemical agent and rare earth particles have a strong chemical reaction, resulting in changes in the structure of the rare earth, and thus affecting the macroscopic mechanical properties and [...] Read more.
In the process of ion-adsorbed rare earth (RE) ore leaching and mining, the injected chemical agent and rare earth particles have a strong chemical reaction, resulting in changes in the structure of the rare earth, and thus affecting the macroscopic mechanical properties and permeability of soil. To investigate the evolution of the pore structure during the leaching process, indoor leaching simulation experiments were used to compare and analyze the changes of Zeta potential during the leaching process with different concentrations of leaching solution, the process of the gradual change of the strong and weak combined water layer was analyzed, and a nuclear magnetic resonance (NMR) instrument was used to obtain the structural parameters such as the porosity, T2 spectrum and pore radius to analyze the evolution law of microscopic pore structure. The experimental results show that the deionized (DI) water leaching process has less effect on the pore structure of the ore body, and the pore structure inside the ore body evolves gradually from small and medium pore size pores to large pore size pores, while the pore structure of the ore body changes more during the leaching process of the MgSO4 leaching solution. In the initial leaching stage, the number of minimal pores (0–0.24 μm) and small pores (0.24–0.65 μm) of the ore body decreases rapidly, and the number of large pores (1.6–10 μm) increases. In the effective leaching stage, the number of minimal pores (0–0.24 μm), small pores (0.24–0.65 μm) and medium pores (0.65–1.6 μm) increases, while the number of large pores (1.6–10 μm) and mega pores (greater than 10 μm) decreases. At the end of leaching stage, the pore size evolves from medium pores (0.65–1.6 μm) and small pore (0.24–0.65 μm) to large pores (1.6–10 μm). Both chemical replacement reaction and solution percolation can induce changes in the pore structure of the ore body, and the influence of the chemical replacement reaction is higher than that of percolation in the leaching process. The evolution of pore structure during ion exchange is caused by the difference of ionic strength in leaching solution. RE ore particles are adsorbed or released to the solid phase, and the migration of particles leads to changes in the interface properties of RE particles, which affects the pore structural changes. Full article
(This article belongs to the Special Issue Recent Developments on the Leaching Process of Rare Earth Ore)
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14 pages, 5378 KiB  
Article
Effect of Magnesium Sulfate Solution on Pore Structure of Ionic Rare Earth Ore during Leaching Process
by Zhongquan Gao, Yunzhang Rao, Liang Shi, Run Xiang and Zhihua Yang
Minerals 2023, 13(2), 294; https://doi.org/10.3390/min13020294 - 20 Feb 2023
Cited by 4 | Viewed by 1453
Abstract
During in situ leaching of ionic rare earth ore, the pore structure of the orebody changes due to the chemical replacement reaction between the leaching agent and the rare earth ore. To explore the influence of leaching agents on the pore structure of [...] Read more.
During in situ leaching of ionic rare earth ore, the pore structure of the orebody changes due to the chemical replacement reaction between the leaching agent and the rare earth ore. To explore the influence of leaching agents on the pore structure of ionic rare earth ore during the leaching process, magnesium sulfate solutions with different concentrations and pH are used as leaching agents in this paper. An experimental method of indoor simulated column leaching, a Zetaprobe potential analyzer, and an NM-60 rock microstructure analyzer to measure parameters, including surface zeta potential, T2 map, and the pore structure of rare-earth ore particles, were used to analyze the influence law of magnesium sulfate solution on the pore structure of ionic rare earth ore. The result proves that pure H2O leaching has little effect on the surface Zeta potential and the internal pore structure of the ore particles. In the leaching process of magnesium sulfate solutions with different concentrations, the absolute value of Zeta potential decreases, and the internal pore structure evolves from medium, large, and extra-large to small pores. In the leaching process of magnesium sulfate solutions with different pH, the absolute value of Zeta potential decreases and then increases slightly with the end of the ion exchange reaction. The internal pore structure generally shows a decrease in the number of small and extra-large pores and an increase in the number of medium and large pores. According to the analysis, the concentration and pH of the leaching agent cause the change of thickness of the electric double layer of the fine particles in the orebody, break the balance of interaction force between soil particles, and result in the evolution of a micropore structure of orebody during leaching. Full article
(This article belongs to the Special Issue Recent Developments on the Leaching Process of Rare Earth Ore)
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15 pages, 5821 KiB  
Article
An Early Warning System for Landslide Risks in Ion-Adsorption Rare Earth Mines: Based on Real-Time Monitoring of Water Level Changes in Slopes
by Min Han, Yunzhang Rao, Wen Nie, Dan Wang, Fuyu Wu and Liang Shi
Minerals 2023, 13(2), 265; https://doi.org/10.3390/min13020265 - 14 Feb 2023
Viewed by 1343
Abstract
During the in situ leaching process of ion-adsorption rare earths, leaching solution needs to be constantly injected to the mine slopes. As a consequence, landslides are highly likely to occur due to the increasing water level of soil mass. To solve this problem, [...] Read more.
During the in situ leaching process of ion-adsorption rare earths, leaching solution needs to be constantly injected to the mine slopes. As a consequence, landslides are highly likely to occur due to the increasing water level of soil mass. To solve this problem, we conducted a mechanical analysis on the rising water level after solution injection, which shed light on the mechanical principle of slope instability brought about by rising water level. With water level variation as the major factor, we established an early warning system for landslide risks on the basis of the real-time monitoring of water level. Within the system, a self-designed landslide early warning model is embedded. In addition to monitoring the water level variation in slopes, this system can be employed for real-time data processing. With the integration of early warning model algorithm, the real-time graded early warning of slope landslide risks is achieved within the mining process of ion-adsorption rare earths. By discussing the real-time monitoring method, framework of landslide early warning system, FIFC landslide early warning model, optimization method of water level, and selection of landslide-inducing factors, this research provides an effective solution to the landslide early warning within the mining process of ion-adsorption rare earth minerals. Thus, it can be employed as a favorable reference for other types of early warning systems. Full article
(This article belongs to the Special Issue Recent Developments on the Leaching Process of Rare Earth Ore)
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15 pages, 12016 KiB  
Article
Simulation of an Ionic Rare Earth Leaching Process Based on the Darcy Law-Chemical Reaction Engineering-Transfer of Dilute Substance Coupling
by Dan Wang, Fuyu Wu, Yunzhang Rao, Wei Xu, Min Han and Liang Shi
Minerals 2022, 12(12), 1500; https://doi.org/10.3390/min12121500 - 24 Nov 2022
Cited by 3 | Viewed by 1501
Abstract
The basic principle of in situ leaching is chemical mining. The process of in situ leaching is to inject leaching solution into the ore body, and the leaching solution is spread in the pores of the mountain. The process is completed by the [...] Read more.
The basic principle of in situ leaching is chemical mining. The process of in situ leaching is to inject leaching solution into the ore body, and the leaching solution is spread in the pores of the mountain. The process is completed by the coupling action of the liquid seepage field and ion exchange reactions. In the production process, only one injection of liquid can be carried out in a certain stope, so it is impossible to improve the injection process and leaching effect through field practice. By simulating the in situ leaching process of rare earth ions, this paper builds the test stope true three-dimensional numerical model and simulates the leaching process of rare earth ore under the coupling of seepage control, ion exchange, and dilute material transfer in porous media. The migration rule of RE3+ and Mg2+ in stopes was analyzed to evaluate the leaching effect. It is of great significance to increase the recovery rate of rare earth ore. Full article
(This article belongs to the Special Issue Recent Developments on the Leaching Process of Rare Earth Ore)
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Review

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15 pages, 1565 KiB  
Review
Development Review on Leaching Technology and Leaching Agents of Weathered Crust Elution-Deposited Rare Earth Ores
by Zhigao Xu, Gang Li, Huifang Yang, Aoyang Sha, Zhengyan He, Yuchen Tang, Ming Wu and Jun Qu
Minerals 2023, 13(9), 1223; https://doi.org/10.3390/min13091223 - 17 Sep 2023
Viewed by 1456
Abstract
Weathered crust elution-deposited rare earth ores are key strategic resources and the main source of medium and heavy rare earths. This paper summarizes the development of leaching technology of rare earth ores, compares the advantages and disadvantages of the three generations of leaching [...] Read more.
Weathered crust elution-deposited rare earth ores are key strategic resources and the main source of medium and heavy rare earths. This paper summarizes the development of leaching technology of rare earth ores, compares the advantages and disadvantages of the three generations of leaching technology, and introduces the improved heap leaching technology and the new technology of the leaching–extraction integration and enhanced leaching, focusing on the leaching of weathered crust elution-deposited rare earth ores. In this paper, the development of the leaching agents is expounded, and the research status and the development trend of the composite ammonium salt leaching agent, impurity inhibition leaching agent, swelling inhibition leaching agent, and seepage-promotion leaching agent are also introduced. And this paper summarizes the leaching mechanism and the development direction of leaching agents. Moreover, the future key research direction of weathered crust elution-deposited rare earth ores is proposed, which is green, efficient, safe development and utilization. Full article
(This article belongs to the Special Issue Recent Developments on the Leaching Process of Rare Earth Ore)
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