Rare Earth Research Articles

Pre-concentration of REE values from nepheline syenite rocks of western Odisha, India

ABSTRACT The rare-earth elements (REEs) have gained enormous economic and scientific attention due to their distinct properties and new applications. Nepheline syenite rock is an important primary source of rare earth minerals. The nepheline syenite rocks from the Rairakhol area, western Odisha, have been characterized for their rare earth mineralogical and textural characteristics. Preliminary beneficiation studies of these rocks were carried out to upgrade the REE values using falcon gravity separation and floatation technique. Hornblende, biotite, K-feldspar, albite, and nepheline are the major mineral constituents of the nepheline syenite where REE-bearing minerals occur as accessory minerals. The REE mineral phases present are zircon, sphene, apatite, allanite, britholite, and REE phosphate, with grain sizes ranging from 10 to 50 microns. Allanite and britholite occupy the intergranular spaces of major mineral phases and occur as thin lines or veins whereas sphene and zircon occur as inclusions within major mineral phases. The flotation study shows that the total REE content of the froth product could be enriched to 1696 ppm, which is three times more than the total REE content (563 ppm) of the feed sample.

Settling selection of Chlamydomonas reinhardtii for samarium uptake.

Samarium (Sm) is a rare-earth element recently included in the list of critical elements due to its vital role in emerging new technologies. With an increasing demand for Sm, microbial bioremediation may provide a cost-effective and a more ecologically responsible alternative to remove and recover Sm. We capitalized on a previously selected Chlamydomonas reinhardtii strain tolerant to Sm (1.33 × 10-4 M) and acidic pH and carried out settling selection to increase the Sm uptake performance. We observed a rapid response to selection in terms of cellular phenotype. Cellular size decreased and circularity increased in a stepwise manner with every cycle of selection. After four cycles of selection, the derived CSm4 strain was significantly smaller and was capable of sequestrating 41% more Sm per cell (1.7 × 10-05 ± 1.7 × 10-06 ng) and twice as much Sm in terms of wet biomass (4.0 ± 0.4 mg Sm · g-1) compared to the ancestral candidate strain. The majority (~70%) of the Sm was bioaccumulated intracellularly, near acidocalcisomes or autophagic vacuoles as per TEM-EDX microanalyses. However, Sm analyses suggest a stronger response toward bioabsorption resulting from settling selection. Despite working with Sm and pH-tolerant strains, we observed an effect on fitness and photosynthesis inhibition when the strains were grown with Sm. Our results clearly show that phenotypic selection, such as settling selection, can significantly enhance Sm uptake. Laboratory selection of microalgae for rare-earth metal bioaccumulation and sorption can be a promising biotechnological approach.

Modulating the size distribution of preformed BaHfO3 nanocrystals towards effective flux pinning in MOD-derived YBCO-coated conductors

Abstract The added BaMO3 (BMO, M =Zr, Hf) nanocrystals into REBa2Cu3O7-δ (REBCO, RE=Y or other rare earth) superconducting films by the technology of preformed nanocrystal addition from colloidal precursor solutions have coarsened after sintering of the REBCO films, which limit the BMO size control and flux pinning enhancement. In the present work, the evolution of the size of BaHfO3(BHO) nanocrystals in the YBCO films is studied. The collection process of BHO nanocrystals is optimized to successfully separate BHO with an average size of 6 nm into two parts with average sizes of 4.5 nm and 7.7 nm, respectively. The evolution of three different BHO sizes in YBCO superconducting films with a thickness of 2.2 μm and 10 mol% addition reveals that the small-size preformed nanocrystals decomposed at high temperatures to release Hf ions, resulting in the coarsening of other preformed BHO nanocrystals. After modulating the BHO size by reducing the amount of small-size BHO, the coarsening factor is reduced from 1.6 to 1.1, leading to a better in-field performance, especially at low temperatures. At 30 K@1 T, the critical current density (J c) of the 7.7 nm BHO-added YBCO increases by 23% and 50% than cases of 6 nm and 4.5 nm, respectively, being of great guiding value in the technology of performed nanocrystal addition.

A comprehensive study of apatite grains in Ryugu rock fragments

AbstractApatite is present as an accessory phase in many meteorites and is often formed as a secondary product of aqueous alteration. Its propensity to incorporate rare earth elements (REE) results in apatite usually being the main REE‐bearing phase in hydrously altered meteorites. Asteroid Ryugu is thought to have experienced pervasive aqueous alteration and material collected from the surface of Ryugu is expected to provide insight into asteroidal aqueous alteration processes without influence by terrestrial weathering. Morphologies and mineral associations of apatite grains from five rock fragments collected from the asteroid Ryugu by the Hayabusa2 spacecraft were examined and their REE concentrations were measured by synchrotron X‐ray fluorescence (SXRF) spectroscopy. The main minerals associated with apatite are dolomite, magnetite, and pyrrhotite. Grain boundary corrosion of the interfaces between apatite assemblages and the surrounding matrix suggest that paragenetic formation on the asteroid was followed by a later episode of hydrous alteration. Light REE (LREE) concentration levels recorded at 20–150 times those of bulk CI levels together with a steady increase from LREE toward enrichment of medium REE (MREE, up to Er) at 50–400 times bulk CI levels may suggest postgenetic removal of LREE from Ryugu apatite grains by late‐stage circulation of a hydrothermal fluid.

Provenance of mixed volcaniclastic-carbonaticlastic gravity-flow deposits: a case study from the Cretaceous of the southern Central Alborz (Iran)

ABSTRACT Understanding the petrographic and geochemical characteristics of different tectonic settings is essential to improving traditional methods of identifying the provenance of palaeo-sedimentary environments. This research focuses on the K2b unit, which consists of mixed carbonate and volcanic lithic sandstones located in Iran with the age of the Turonian-Early Campanian period. Five sedimentary lithotypes with distinct petrographic and geochemical signatures were identified in the Turonian/Lower Campanian K2b unit, which consists of coarse-grained fan-delta strata. Carbonate and volcanic lithic fragments are the most characteristic components of mostly quartzo-lithic to felspatho-litho-quartzose sandstone layers, documenting a unidirectional paleocurrent pattern with the north-eastward direction. The original composition has undergone diagenesis, resulting in the precipitation of authigenic carbonates and depleting Rare Earth Elements (REE) except for Eu, which shows a positive anomaly. The K2b fan delta was situated on the margin of the proto-south Caspian back-arc basin, and the sediments were sourced from the undissected magmatic arc. The gravity flow deposits in the K2b unit were likely triggered by tectonic activity in the catchment area of the fan delta, leading to uplift and formation of relief associated with the regional Mosha Fault and, on a larger palaeogeographic scale, with subduction of the Arabian plate beneath the Iranian plate during Turonian-Early Campanian.

Near-Infrared Luminescent Materials Incorporating Rare Earth/Transition Metal Ions: From Materials to Applications.

Near-infrared materials exhibiting high photoluminescence quantum yields present a promising avenue to broaden our capacity and threshold for detection and manipulation, extending beyond the visible emission range. The spotlight has shifted to near-infrared (NIR) luminescent materials emitting beyond 1000nm, with growing interest due to their unique characteristics. The ability of NIR-II emission (1000-1700nm) to penetrate deeply and transmit independently positions these NIR luminescent materials for applications in optical-communication devices, bioimaging, and photodetectors. The combination of rare earth metals/transition metals with a variety of matrix materials provides a new platform for creating new chemical and physical properties for materials science and device applications. In this review, we summarize the recent advancements in NIR emission activated by rare earth and transition metal ions and illustrate their role in applications spanning bioimaging, sensing, and optoelectronics. We start from the various synthesis techniques, including high-temperature solid-state, hydrothermal, and thermal decomposition methods, on how to delicately incorporate the rare-earth/transition metals to the NIR various matrixes, each imparting distinct characteristics to these luminescent materials. We then extend the discussion to strategies of enhancing excitation absorption and emission efficiency, spotlighting innovations like dye sensitization and surface plasmon resonance effects. Subsequently, a significant focus is placed on functionalization strategies and their applications. Finally, we provide a comprehensive analysis of the challenges and proposed strategies for rare earth/transition metal ion-doped near-infrared luminescent materials, summarizing the insights of each section. This article is protected by copyright. All rights reserved.

Effect of Hydrogenation on the Magnetic and Magnetocaloric Properties of Rare Earth Intermetallic Compounds Tb0.33Ho0.33Er0.33Ni and Dy0.33Ho0.33Er0.33Ni

Effect of Hydrogenation on the Magnetic and Magnetocaloric Properties of Rare Earth Intermetallic Compounds Tb0.33Ho0.33Er0.33Ni and Dy0.33Ho0.33Er0.33Ni

Direct observation and characterization of a novel long period stacking ordered phase in GH4169 alloy

As is widely recognized, the Long Period Stacking Ordered (LPSO) phase is an important strengthening phase in the rare earth magnesium alloys. The LPSO phase not only enhances the strength of the alloy, but also improves its plasticity, thereby effectively addressing the strength-ductility trade-off phenomenon. Therefore, the preparation of metallic materials containing LPSO phase provides a new idea for designing a new generation of high-strength and high-toughness alloys. In present study, A novel nano-sized LPSO phase is observed and characterized for the first time in GH4169 nickel-based alloy. The results show that the stacking sequence of the LPSO phase is ABCBCBA, which indicates that this LPSO phase has a 6H structure. Meanwhile, the orientation relationships between LPSO phase and the Ni matrix are (11–1)γ//(0006)LPSO and [011]γ//[2-1-10]LPSO.

Tunable magnetism in titanium-based kagome metals by rare-earth engineering and high pressure

Rare-earth engineering is an effective way to introduce and tune magnetism in topological kagome materials, which have been acting as a fertile platform to investigate the quantum interactions between geometry, topology, spin, and correlation. Here, we report the synthesis, structure, and physical properties of titanium-based kagome metals RETi3Bi4 (RE = Yb, Pr, and Nd) with various magnetic states. They all crystallize in the orthogonal space group Fmmm (No. 69), featuring distorted titanium kagome lattices and rare-earth zig-zag chains. By changing the rare earth atoms in the zig-zag chains, the magnetism can be tuned from nonmagnetic YbTi3Bi4 to short-range ordered PrTi3Bi4 (Tanomaly ~ 8.2 K), and finally to ferromagnetic NdTi3Bi4 (Tc ~ 8.5 K). In-situ resistance measurements of NdTi3Bi4 under high pressure further reveal a tunable ferromagnetic ordering temperature. These results highlight RETi3Bi4 as a promising family of kagome metals to explore nontrivial band topology and exotic phases.

Acid Leaching of La and Ce from Ferrocarbonatite-Related REE Ores

Rare earth elements comprise a group of 17 chemically similar elements, which increases the difficulty of separating them by traditional methods. For this reason, hydrometallurgy has been the most used method. However, it is important to evaluate the efficiency of the leaching processes used because, in addition to depending on the operating parameters of the leaching, they also depend on the mineralogical composition of the sample. In the present work, the extraction of Ce and La contained in the ferrocarbonatite mineral from the north of Mexico was studied. For the leaching tests, several leaching agents were used (HCl, H2SO4, HNO3, and H3PO4 in different concentrations (0.5 [M], 1 [M], 1.5 [M]) and the temperature was modified to 20, 40, and 60 °C. A maximum recovery of 70% for Ce and La was obtained using HCl 1M in 4 h. The results of the kinetic study of the experiments showed that the best fitting model according to these kinetic models was the SCM controlled by a chemical reaction.

Study of the Adsorption and Separation Behavior of Scandium and Zirconium by Trialkyl Phosphine Oxide-Modified Resins in Sulfuric and Hydrochloric Acid Media

Zirconium is recognized as one of the main impurities of the rare earth element scandium during purification. It presents significant challenges due to its similar chemical properties, making separating it difficult. This study used trialkyl phosphine oxide (TRPO) as a functional ligand, and the effects of carrier type and acidity on adsorption performance were first investigated. Among these, the novel extraction resin SiO2-P as a carrier for TRPO demonstrated more prominent separation performance in 0.2 M H2SO4 and 5 M HCl solutions. The kinetic and isotherm data were consistent with the pseudo-secondary kinetics and Langmuir model, respectively, and the adsorption process could be regarded as homogeneous monolayer adsorption subject to the dual effects of chemisorption and internal diffusion. In addition, thermodynamic analysis showed that the adsorption process of zirconium under the experimental conditions was a spontaneous endothermic process. Combined with the results of SEM-EDS, FT-IR, and XPS analyses, scandium and zirconium were successfully adsorbed by the resin and uniformly distributed on its surface, and the greater affinity of the P=O groups on the resin for zirconium was the critical factor contributing to the separation of scandium and zirconium. Finally, scandium and zirconium in sulfuric acid and hydrochloric acid media were extracted and separated by column experiments, and the purity of scandium could reach 99.8% and 99.99%, respectively.

Superconductivity of thulium substituted clathrate hexahydrides at moderate pressure

Due to the BCS theory, hydrogen, the lightest element, would be the prospect of room-temperature superconductor after metallization, but because of the difficulty of the hydrogen metallization, the theory about hydrogen pre-compression was proposed that the hydrogen-rich compounds could be a great option for the high Tc superconductors. The superior properties of TmH6, YbH6 and LuH6 indicated the magnificent potential of heavy rare earth elements for low-pressure stability. Here, we designed XTmH12 (X = Y, Yb, Lu, and La) to obtain higher Tc while maintaining low pressure stability. Most prominently, YbTmH12 can stabilize at a pressure of 60 GPa. Compared with binary TmH6 hydride, its Tc was increased to 48 K. The results provide an effective method for the rational design of moderate pressure stabilized hydride superconductors.

Role of Dy 4f electrons on magnetic coupling and reorientation in DyFeO3.

Spin reorientation transition is an ubiquitous phenomenon observed in magnetic rare earth orthferrites RFeO3, which has garnered significant attention in recent years due to the potential applications in spintronics or magnetoelectric devices. Although a plenty of experimental works suggest that the magnetic interaction between R3+ and Fe3+ spins is at the heart of the spin reorientation, but a direct and decisive support from theoretical side is lacking so far, owning to the tricky handling of R 4f electrons. In this paper, we explored DyFeO3 as an example by means of comprehensive first principles calculations, and compared two different recipes, where the Dy 4f electrons are separately treated as core or valence states, respectively, in order to highlight what the role of Dy 4f electrons plays in, especially the spin reorientation transition. The comparison provides a solid piece of evidence for the experimental argument that the Dy3+-Fe3+ magnetic interactions play a vital role in triggering spin reorientation of Fe moments at low temperature. The findings revealed here not only extend our understanding on the underlying mechanism for spin reorientation transition in RFeO3, but also highlight the importance of explicit description of R 4f electrons in rationally reproducing their structural, electronic and magnetic properties.

Effectiveness Evaluation of Pyrometallurgy and Hydrometallurgy Methods in The Recycling Process of Nd-Fe-B Permanent Magnet and Rare Earth Metals Recovery : A Review

Effectiveness Evaluation of Pyrometallurgy and Hydrometallurgy Methods in The Recycling Process of Nd-Fe-B Permanent Magnet and Rare Earth Metals Recovery : A Review

Afghanistan’s raw materials policy regarding rare earth elements after the Taliban victory [Polityka surowcowa Afganistanu dotycząca metali ziem rzadkich po zwycięstwie Talibów

The Taliban victory in Afghanistan in 2021 has not only raised geopolitical concerns but has also sparked questions about the state’s policies and strategies concerning its rare earth elements reserves. The main objective of the presented article is to indicate how the current political change in Afghanistan may affect the raw material policy regarding the extraction of rare earth elements, taking into account geopolitical factors. Rare earth elements are a group of critical minerals that are of great importance to modern technologies, ranging from electronics and renewable energy to defence systems. Afghanistan is known to possess significant deposits of these valuable resources, which have the potential to play a crucial role in global supply chains, especially in the face of ongoing rivalry between the People’s Republic of China and the United States of America. The research problem of the considerations undertaken in this article is to assess the key challenges and opportunities in harnessing Afghanistan’s rare earth element resources after the Taliban’s return to power. The research conducted shows that despite having a significant amount of rare earth elements, Afghanistan lacks the infrastructure necessary to extract and process these valuable minerals. After the Taliban victory, the newly established government sees the potential benefit in extracting rare earth elements and is willing to align itself with China to exploit them.

Study on the adsorption/desorption characteristics and dynamic diffusion mechanism of rare earth hydrated ions on the kaolinite (001) surface

Coal gangue (CG) contains abundant rare earth elements (REEs), which is a potential REE resource. REEs are mainly present in clay minerals as hydrates. The adsorption, desorption, and diffusion of REEs-hydrates on the surface of clay minerals are the key to regulating the leaching effect of REEs. The paper focuses on the typical clay minerals kaolinite and REEs-hydrates and combines quantum mechanics and molecular dynamics methods to systematically study the adsorption, desorption, and dynamic diffusion behavior of REEs-hydrates in acid solution. The research results indicate that stable REEs-hydrates La(H2O)9 and Y(H2O)7 are formed, with ion bonds between REEs and water molecules. La(H2O)9 and Y(H2O)7 mainly interact with the kaolinite (001) surface through hydrogen bonding. Competitive adsorption is formed between water molecules, hydrated hydrogen ions, and REEs-hydrates. Water molecules and hydrated hydrogen ions occupy the adsorption active sites of REEs-hydrates and form a dense water molecular layer on the surface. The distance between H3O+ and REEs-hydrates and the number of H3O+ in the solvent layer affect the desorption and diffusion behavior of hydrates. The bonding law, dynamic desorption, and diffusion mechanism of REEs-hydrates can provide meaningful references for selective leaching of REEs from CG.

Crystallisation behaviour and enhanced separation of RE-phase in RE-bearing blast furnace slag

With the wide application and consumption of rare earths (REs), the secondary resources of RE-bearing blast furnace slag are being investigated as viable resources for the recovery of these critical elements. In this study, the crystallisation behaviour including nucleation and growth kinetics of the RE-phase in RE-bearing blast furnace slag was studied and the optimal precipitation conditions for the RE-phase during the cooling process was obtained, providing an important reference and guidance for the efficient extraction and subsequent functionalised reuse of REs. Subsequently, the supergravity enhanced separation of RE-phase from the slag system was conducted in the optimal precipitation conditions of cooling rate (2 °C/min), experiment temperature (1200 °C), and holding time (100 min). At G = 1000, the RE-phase was successfully separated from molten slag, and the mass fraction of CeO2 in the separated sample increased from the original 20.51% to 74.85%, and the recovery ratio reached 92.06%. This indicated that the supergravity separation technology is considered to be an effective technology for the enrichment and recovery of REs from RE-bearing blast furnace slag.

Some Recent Advances in Germanium Recovery from Various Resources

Though nowadays germanium does not reach the range of popularity of other metals, i.e., rare earth elements, its utility in target industries makes it a strategic metal. Though germanium can be found in a series of raw materials, the principal source for its recovery is from secondary wastes of the zinc industry; also, the recyclability of germanium-bearing waste materials is becoming of interest. In this recovery and due to the size of the target materials, because the diffusion and reaction are to be considered, hydrometallurgy performs a key role in achieving this goal. The present work reviews the most recent applications (2023 and 2024 years) of hydrometallurgical operations on the recovery of germanium from different solid and liquid sources.

High-Temperature Cyclic Oxidation Behavior and Microstructure Evolution of W- and Ce-Containing 18Cr-Mo Type Ferritic Stainless Steel

Due to the recurrent starting and stopping operations of automobiles during service, their engines’ hot ends are continually subjected to high-temperature cyclic oxidation. Therefore, it is crucial to develop ferritic stainless steels with better high-temperature oxidation resistance. This study focuses on improving the high-temperature cyclic oxidation performance of 18Cr-Mo (444-type) ferritic stainless steel by alloying with high-melting-point metal W and the rare earth element Ce. For this purpose, a high-temperature cyclic oxidation experiment was designed to simulate the actual service environment and investigate the high-temperature cyclic oxidation behavior and microstructure evolution of 444-type ferritic stainless steel alloyed with W and Ce. The oxide structure and composition formed during this process were analyzed and characterized using scanning electron microscopy/energy dispersive spectroscopy (SEM-EDS) and electron probe X-ray micro-analyzer (EPMA), in order to reveal the mechanism of action of W and Ce in the cyclic oxidation process. The results show that 18Cr-Mo ferritic stainless steel alloyed with W and Ce exhibits an excellent resistance to high-temperature cyclic oxidation. The element W can promote the precipitation of the Laves phase between the matrix and the oxide film, and the small-sized Laves phase can inhibit the interfacial diffusion of oxidation reaction elements and prevent the inward growth of the oxide film. The element Ce can refine oxide particles and reduce the thickness of the oxide film. CeO2 particles within the oxide film can serve as nucleation sites for the formation of oxide particles from reactive elements, and they also contribute to pinning the oxide film, thereby enhancing its adhesion.

Assessing teratogenic risks of gadolinium in freshwater environments: Implications for environmental health

Gadolinium (Gd) is among the rare earth elements extensively utilized in both industrial and medical applications. The latter application appears to contribute to the rise in Gd levels in aquatic ecosystems, as it is excreted via urine from patients undergoing MRI scans and often not captured by wastewater treatment systems. The potential environmental and biological hazards posed by gadolinium exposure are still under investigation. This study aimed to assess the teratogenic risk posed by a gadolinium chelate on the freshwater cnidarian Hydra vulgaris. The experimental design evaluated the impact of pure Gadodiamide (25 μg/l, 50 μg/l, 100 μg/l, 500 μg/l) and its commercial counterpart compound (Omniscan®; 100 μg/l, 500 μg/l, 782.7 mg/l) at varying concentrations using the Teratogenic Risk Index (TRI). Here we showed a moderate risk (Class III of TRI) following exposure to both tested formulations at concentrations ≥ 100 μg/l. Given the potential for similar concentrations in aquatic environments, particularly near wastewater discharge points, a teratogenic risk assessment using the Hydra regeneration assay was conducted on environmental samples collected from three rivers (Tiber, Almone, and Sacco) in Central Italy. Additionally, chemical analysis of field samples was performed using ICP-MS. Analysis of freshwater samples revealed low Gd concentrations (≤ 0.1 μg/l), despite localized increases near domestic and/or industrial wastewater discharge sites. Although teratogenic risk in environmental samples ranged from high (Class IV of TRI) to negligible (Class I of TRI), the low Gd concentrations, particularly when compared to higher levels of other contaminants like arsenic and heavy metals, preclude establishing a direct cause-effect relationship between Gd and observed teratogenic risks in environmental samples. Nevertheless, the teratogenic risks observed in laboratory tests warrant further investigation.