Search Results (147)

The mining sequence of ionic rare earth mineral mining districts is related to the effective utilization of rare earth mineral resources and the protection of ecological environment. This study establishes an optimization model for the mining sequence of ion-adsorption rare earth mining districts that incorporates environmental costs, using the net present value (NPV) of the mining district and the net present value of environmental costs (C_E) as objective functions. The model is applied to optimize the mining sequence of Mining District L. The results demonstrate that (1) Four algorithms, namely NSGA-II, NSGA-III, IBEA, and MOEA/D, were selected for comparison. The analysis based on the distribution of solutions, hypervolume values (HV), and computational time revealed that the IBEA exhibited superior performance. (2) The IBEA was employed to solve the multi-objective optimization problem, yielding a set of 30 optimal solutions. Different NPVs corresponded to different C_E values, with the C_E value increasing correspondingly as the NPV increased. (3) The weighted method was employed to transform the multi-objective optimization problem into a single-objective formulation. Using a genetic algorithm (GA), the optimal solution yielded a decision variable sequence for mining order as [2, 5, 8, 4, 1, 9, 6, 7, 3, 10, 11], with the net present value (NPV) of mining district profits reaching CNY 76,640.65 million and the environmental cost NPV amounting to CNY 19,469.18 million. Compared with the mining sequence optimization scheme that did not consider C_E, although the NPV decreased by CNY 3.3266 million, the C_E was reduced by CNY 10.6993 million. The mining sequence optimization model with environmental costs constructed in this paper provides a scientific decision-making basis for mining enterprises to consider the mining sequence in mining districts, minimize the damage to the ecological environment, and promote the coordinated progress of resource development and sustainable development. Full article

Bacillus species have shown the potential to recover rare earth elements (REEs), but strains with adsorption selectivity for terbium(III) remain understudied. In this study, six Bacillus strains with the capability for efficient adsorption of Tb(III) were screened from an ionic rare earth mine and were identified based on 16S rRNA gene sequencing. Adsorption experiments showed that Bacillus sp. DW011 exhibited exceptional Tb(III) adsorption efficiency, with an adsorption rate of 90.45% and adsorption selectivity for heavy rare earth elements. Notably, strain DW011 was also found to be tolerant against Tb(III) with the 24 h 50% lethal concentration (LC₅₀) of 2.62 mM. The biosorption mechanisms of DW011 were investigated using adsorption kinetics, SEM-EDS, and FTIR. The results indicated that the adsorption of strain DW011 conforms to the second-order kinetic model, and the teichoic acid–peptidoglycan network (phosphate-dominated) serves as the primary site for heavy REE adsorption, while carboxyl/amino groups in the biomembrane matrix provide secondary sites for LREEs. This study provides new information that Bacillus strains isolated from ionic rare earth mine deposits have potential as green adsorbents and have high selectivity for the adsorption of heavy REEs, providing a sustainable strategy for REE recovery from wastewaters. Full article

The shear strength properties of ionic rare earth ore bodies are directly related to the stability of mine slopes, which provides important theoretical and engineering support for preventing geological disasters and ensuring the safe extraction of resources. This study investigates the effects of different confining pressures, leaching agent types, and MgSO₄ concentrations on the shear strength of ionic rare earth ores through triaxial shear tests. A scanning electron microscopy (SEM) analysis of post-shear mineral samples was conducted to examine the microscopic pore structure, revealing the evolution patterns of the ionic rare earth ore’s microscopic pore structure under various leaching conditions. The results show that the shear strength of the ore body varies significantly under different leaching conditions. After leaching, the shear strength values of the ore body, ranked from highest to lowest, are (NH₄)₂SO₄ > MgSO₄ > Al₂(SO₄)₃ > pure water. The (NH₄)₂SO₄ leaching group exhibited an average shear strength approximately 9.8% higher than the pure water group. When comparing the cohesion and internal friction angle of the pure water leaching group, the (NH₄)₂SO₄-leached ore body showed significantly higher cohesion and a smaller internal friction angle. In contrast, the MgSO₄ and Al₂(SO₄)₃ leaching groups demonstrated lower cohesion and higher internal friction angles. As the MgSO₄ concentration increases, the cohesion of the ore body gradually decreases, the internal friction angle increases, and the shear strength correspondingly increases. Under low-concentration MgSO₄ leaching, the number and area of pores in the ore samples initially increase and then decrease, leading to a more complex pore structure. At higher concentrations of MgSO₄, the variety of pore shapes increases and becomes more complex, pore randomness decreases, the probability entropy value decreases, and the pore distribution becomes more ordered. Full article

Cobalt telluride (CoTe₂) is considered an advanced anode material for sodium-ion batteries (SIBs) because of its high theoretical capacity and high conductivity. Nevertheless, the ionic radius of the Co²⁺ ion (0.74 Å) is smaller than that of the Na⁺ ion, meaning the integrity of CoTe₂ electrodes can be easily damaged when Na⁺ ions diffuse into CoTe₂ and convert to large Na₂Te. Herein, we propose a doping strategy by introducing an unreactive element but with a large radius to enhance the overall performance. Lanthanum (La) can be doped into the CoTe₂ structure to counteract the size effect of Na₂Te since La has a large radius. On the other hand, La with abundant electrons in CoTe₂ can also facilitate the charge transfer during charge/discharge. As a result, La-doped CoTe₂ (La-CoTe₂) can deliver a maximum capacity of 345 mAh g⁻¹ at 0.05 A g⁻¹ and has a decent rate performance. After 2000 cycles at 2 A g⁻¹, a capacity of 88 mAh g⁻¹ remained, which is a notable improvement compared to undoped CoTe₂. These results demonstrate the potential of rare earth elements in preparing advanced SIB electrode materials. Full article

The composition of wolframite from ores of the Porokhovskoe and Yugo-Konevskoe W greisen deposits in the Central Urals is studied using SEM-EDS and LA-ICP-MS analyses. The Porokhovskoe deposit is localized in a metamorphosed volcanosedimentary sequence of Lower Silurian age, and the Yugo-Konevskoe is enclosed in an eponymous granite pluton of Middle Permian–Lower Triassic age. Most studied wolframite grains belong to hűbnerite. The Fe/(Fe + Mn) value of wolframite varies in a range of 0.02–0.50. Wolframite from both deposits is enriched in Zn, Nb, and Mg. The wolframite from the Porokhovskoe deposit is enriched in V, Sc, Zn, and Mg and is depleted in Mo, U, rare earth elements (REEs), Nb, and Ta, compared to wolframite from the Yugo-Konevskoe deposit. It is suggested that this difference is due to the occurrence of ore veins in different rocks at different distance from the source of the ore-forming fluid, which cools down as it moves away from the source, leading to a decrease in the incorporation of trace elements by the lower-temperature wolframite. The predominance of heavy REEs over light REEs in all the studied wolframite is explained by the close ionic radii of heavy REEs to the main mineral-forming elements Fe and Mn. Full article

Ionic rare earth ores are primarily extracted through in situ shallow well leaching. The leaching solutions engage in a physical–chemical coupling effect with the rare earth ores, which diminishes the strength parameters of weathered ore layers. This reduction in strength leads to a decrease in the stability of the slope and an increased risk of landslides, significantly contributing to instability and damage within rare earth mines. This study employs Geo-Studio 2020 software to analyze the stability of the rare earth mine slope. A seepage field under natural conditions was simulated during dynamic leaching to evaluate the effects of continuous leaching on stress, displacement fields, and slope stability. The results indicate that the safety factor consistently exceeds the requirement of 1.1 throughout the leaching process, suggesting that the studied slope remains overall stable during the leaching and push-water operation stages. However, substantial deformation may occur at the bottom, middle, and upper sections of the slope, particularly in the rare earth ore and at the interfaces between each layer. Damage is predominantly concentrated in the topsoil and the fully weathered granite zone. Over time, the slope safety factor initially decreases before subsequently increasing. Consequently, targeted landslide prevention measures are essential during the mid to late stages of leaching. Based on the analytical results, measures to enhance slope stability have been proposed, providing theoretical guidance for slope management in in situ leaching mining sites for ionic rare earth ores. Full article

NiAl coatings are critical for protecting components in high-temperature environments. In order to improve the mechanical properties of NiAl coatings, in this study, the elastic and electronic properties of NiAl coatings alloyed with different contents of rare earth element (REE) Y were investigated by using the density functional theory (DFT). It was found that NiAl alloys with 3.125 at.% of Y exhibited higher hardness, while those with 6.25 at.% of Y showed better ductility. This phenomenon is explained by population analysis, which reveals that the covalency of Ni-Ni and Al-Al bonds is stronger in Ni₁₅YAl₁₆ than in Ni₇YA₈, whereas Ni-Al bonds exhibit stronger covalency in Ni₇YAl₈. Additionally, the ionicity of Y-Al bonds is higher in Ni₇YAl₈ than in Ni₁₅YAl₁₆. These results deepen our understanding of how rare earth elements modify the mechanical properties of NiAl alloys, thereby providing a theoretical basis for further exploration of their strengthening mechanisms. Full article

The chemical extraction of rare-earth elements (REEs) from Estonian graptolite-argillite (GA) and phosphate rock (Phosphorite, PH) samples has been conducted and analyzed. For the initial leaching process, HCl and HNO₃ with different concentrations were used to extract REEs from GA and PH. Different extraction agents, including ionic liquids, were examined for the extraction of REEs from acidic aqueous solutions in the liquid–liquid extraction step. After leaching and extraction, all samples were characterized using the inductively coupled plasma mass spectrometry method (ICP-MS/MS). The highest REE extraction efficiencies from GA were established with 1-ethyl-3-methyl imidazolium diethyl phosphate (EMImDEPO₄) and from PH using bis(2-ethylhexyl) phosphate (D2EHPA). Full article

In this review, a comprehensive systematic study of the research background, developments, classification, trends, and advances over the past few years in research on new electromagnetic interference (EMI) shielding materials will be described. The following groups of new materials for EMI shielding will be discussed: biochars, scaffolds, rare earth, and ferrite-based materials. We selected two novel, organic, lightweight materials (biochars and scaffolds) and compared their shielding effectiveness to inorganic materials (ferrite and rare earth materials). This article will broadly discuss the EMI shielding performance, the basic principles of EMI shielding, the preparation methods of selected materials, and their application prospects. Biochars are promising, eco-friendly, sustainable, and renewable materials that can be potentially used as a filter in polymer composites for EMI shielding, along with scaffolds. Scaffolds are new-generation, easy-to-manufacture materials with excellent EMI shielding performance. Rare earth (RE) plays an important role in developing high-performance electromagnetic wave absorption materials due to the unique electronic shell configurations and higher ionic radii of RE elements. Ferrite-based materials are often combined with other components to achieve enhanced EMI shielding, mechanical strength, and electrical and thermal conductivity. Finally, the current challenges and future outlook of new EMI shielding materials will be highlighted in the hope of obtaining guidelines for their future development and application. Full article

In in situ leaching, fine particles can be stripped and transported with the leach solution, significantly altering the particle size distribution and pore structure of each layer of the rare earth ore body. In this study, water and magnesium sulfate were used as leaching agents. Based on indoor column leaching experiments, particle gradation experiments, and pore structure tests, this study investigates and analyzes the patterns of particle migration and changes in pore structure in rare earth ores with varying fine particle contents under leaching conditions. The results indicate that during the leaching process, the degree of change in particle gradation follows the order of upper layer > middle layer > lower layer. As the depth increases, the soil becomes denser, leading to reduced permeability, a slower seepage rate of the leaching solution, and a higher fine particle content, making the effect more pronounced. During magnesium sulfate leaching, the overall trend of porosity in the rare earth ore structure initially increases and then decreases. Additionally, a higher fine particle content corresponds to higher porosity. In the early and late stages of leaching, pore size changes involve the transformation of larger pores into smaller ones, followed by the conversion of smaller pores into larger ones. Moreover, the higher the fine particle content, the greater the degree of transformation between the pore sizes. Full article

On the basis of a microscopic model and employing Green’s function technique, the effects of temperature, size, and ion doping on the magnetization and phonon energy of the A_1g mode in double perovskites Ba₂FeReO₆ and Sr₂CrReO₆—both in bulk and nanoscale samples—are investigated for the first time. The Curie temperature T_C and magnetization M decrease as nanoparticle size is reduced. Doping with rare-earth ions such as Sm, Nd, or La at the Ba or Sr sites further reduces M. This behavior originates from the compressive strain induced by the smaller ionic radii of the dopant ions compared to the host ions. As a result, the antiferromagnetic superexchange interaction between Fe or Cr and Re ions is enhanced, along with an increase in the magnetic moment of the Re ion. The dependence of the band gap energy of Sr₂CrReO₆ on temperature, size, and doping is also studied. Near the magnetic-phase-transition temperature T_C, anomalies in phonon energy and damping indicate strong spin–phonon coupling. The theoretical calculations show good qualitative agreement with experimental data. Full article

Magnesium sulfate leaching of ionic rare earth ores is generally characterized by a smooth outflow curve, a long leaching time, and a high impurity content in the leach liquor. To reveal the leaching law of rare earth cations and impurity aluminum ions in the leaching process of ionic rare earth ores in magnesium sulfate, equilibrium leaching and leaching kinetics experiments were carried out using ore samples of five particle sizes (<0.10, 0.10–0.25, 0.25–0.50, 0.50–1.00, and >1.00 mm). Furthermore, prediction models of equilibrium constants and rate constants were constructed based on ion-exchange theory. The results show that the equilibrium constants of the rare earth and aluminum ion-exchange reactions decrease gradually with the increase in the magnesium ion concentration, the decrease in the temperature, and the increase in the surface area of the particles. Moreover, the equilibrium constant prediction models of rare earth and aluminum with magnesium sulfate were constructed using data fitting. From the leaching kinetics experiment, there is a significant relationship between the reaction rate constant of ion exchange and the surface area of the particles: the larger the particle size, the smaller the reaction rate constant. Based on the kinetic test data and the Arrhenius equation, the frequency factors and activation energies of the ion-exchange reactions were inversely analyzed through the Chemistry Reaction Module of COMSOL. The reaction activation energy for rare earth and aluminum leaching is 10,743 J/mol and 10,987 J/mol, respectively. The rate constant prediction model was obtained by fitting the analyzed rate constant data. The rare earth and aluminum leaching results for the full-grade ores are in high agreement with the predictions of the constructed model, which verifies the validity of the proposed model. This study can provide theoretical support for the improvement of the leaching efficiency of rare earths and the optimization of the magnesium sulfate leaching process. Full article

The permeability of ionic rare is a crucial factor influencing the leaching rate of rare earth elements. In the Gannan region, many ionic rare earth ores exhibit poor permeability and high compressibility compared to sandy soils. The permeability coefficient is a key indicator of the hydraulic performance of these ores. Thus, this study investigates the permeability coefficients of ionic rare earth ores with varying fines contents during the leaching process, with a specific focus on analyzing the impact of fines on permeability performance. To provide a comprehensive assessment of the influence of fines, we prepared ionic rare earth ore samples with fines contents of 5%, 10%, 15%, 20%, 25%, and 30%, ensuring that the overall particle size distributions remained consistent with the original gradation. A constant head permeability test was employed to measure the permeability coefficients of these ore samples throughout the leaching process. We specifically examined how varying fines contents influenced permeability across the upper, middle, and lower layers of the ore body, as well as the overall permeability when subjected to both distilled water and magnesium sulfate solutions. To further elucidate the differences in permeability performance among the various rare earth ore samples, we performed a data fitting analysis of the initial permeability coefficients against fines content, uniformity coefficient, average particle diameter, and void ratio. This analysis aims to quantify the fines effect across different rare earth ores and establish correlations among state parameters, such as fines content, and the initial permeability coefficient. Full article

Ionic rare earth ore (IREO) has a high abundance of medium and heavy rare earth elements (REEs), making it a vital strategic resource for China. In this work, two typical microorganisms, Aspergillus niger and Acidithiobacillus ferrooxidans, were used to study the interaction mechanism during the bioleaching of IREO under acidic conditions. The results revealed some differences in the interaction and leaching effects of A. niger and A. ferrooxidans on ionic rare earth minerals. A. niger mainly forms rare earth complexes with rare earth ions in IREO by secreting metabolites such as organic acids, thereby promoting the release of REEs, and it has a strong adsorption capacity for Yb. A. ferrooxidans promotes the release of REEs from rare earth minerals, primarily through iron–sulfur oxidation. The differential expression of metabolic genes (e.g., gpmL, FabF, FASN) associated with major metabolite secretion indicates their correlation with the leaching process. The above results reveal the role of the typical acid-producing microorganisms A. niger and A. ferrooxidans and their metabolites in the leaching of IREO, which is valuable for understanding the interaction mechanisms between microorganisms and IREO under acidic conditions. Full article

Production of rare earth enrichment from the in situ leaching solution of ion-adsorbed rare earth ores greatly decreases the treatment scale and significantly reduces production energy consumption and cost. However, the generated rare earth enrichment has a high content of impurities. Further purification of rare earth is necessary. Therefore, a process comprised of sulfuric acid leaching and removing aluminum by the neutralization precipitation method to obtain the purified rare earth solution was proposed. The results of acid leaching revealed that at a sulfuric acid concentration of 1.75 mol/L, a temperature of 60 °C, a liquid–solid ratio of 5:1 mL/g, a leaching time of 0.5 h, and a stirring rate of 300 r/min, leaching efficiency of rare earth and magnesium reached 99.11% and 97.39%, respectively, while the leaching efficiencies of aluminum and silicon reached 72.91% and 55.26%, respectively. The comparison of different precipitants during the neutralization precipitation process showed that MgO was the best precipitant for the efficient removal of aluminum and low loss of rare earth. The results of removing aluminum revealed that when the final pH of the rare earth leaching solution was controlled to be 4.7, the reaction temperature was 25 °C, the slurry concentration of MgO was 0.3 mol/L, and the feeding rate of the MgO slurry was 0.5 mL/min, the removal rate of aluminum was 99.49%, and the loss rate of rare earth was 13.93%. The obtained purified rare earth solution contained 19 g/L of rare earth and less than 0.01 g/L of aluminum. Kinetic studies showed that the apparent activation energy of the aluminum removal process was 6.8 kJ/mol, indicating that the precipitation process was controlled by a mass transfer diffusion reaction. Full article