Rare Earth Research Articles

Judicious combinations of gravity, magnetic, electrostatic separators and microwave heat energy on recovery of ilmenite from Humma lean grade beach placer deposit

Microwave heating is an eco-friendly and novel technique for sintering and heating minerals and materials as it has several advantages in terms of phase transformation, energy efficiency, enhancing speed, process simplicity, improved properties. Such heating provides the composite materials to absorb electromagnetic energy volumetrically and transform into heat and produces larger densities as compared to conventional heating. This study focuses on two main objectives: the recovery of ilmenite through a strategic combination of mineral processing equipment, including a spiral concentrator, followed by magnetic and electrostatic separation, and the enhancement of ilmenite concentrate using microwave heat energy on a cleaner magnetic product, followed by electrostatic separation. Continuous magnetic separation results indicate that among the dry high-intensity belt magnetic separator, box mag wet high-intensity magnetic separator and dry rare earth drum magnetic separators, the rare earth magnetic separator yielded the highest quality product. The application of microwave heat energy before the rare earth drum magnetic separator at 1.4 T, followed by high-tension separation, produced the best grade of ilmenite. The magnetic product obtained after microwave treatment contained 98.6% ilmenite, which was further upgraded to a 99.6% ilmenite concentrate through high-tension separation. Therefore, it is recommended that an effective combination of gravity separation, microwave heat energy, rare earth drum dry magnetic separation and high-tension separation be employed to achieve the highest grade of ilmenite concentrate.

Exploring the Potential of Cold Sintering for Proton-Conducting Ceramics: A Review.

Proton-conducting ceramic materials have emerged as effective candidates for improving the performance of solid oxide cells (SOCs) and electrolyzers (SOEs) at intermediate temperatures. BaCeO3 and BaZrO3 perovskites doped with rare-earth elements such as Y2O3 (BCZY) are well known for their high proton conductivity, low operating temperature, and chemical stability, which lead to SOCs' improved performance. However, the high sintering temperature and extended processing time needed to obtain dense BCZY-type electrolytes (typically > 1350 °C) to be used as SOC electrolytes can cause severe barium evaporation, altering the stoichiometry of the system and consequently reducing the performance of the final device. The cold sintering process (CSP) is a novel sintering technique that allows a drastic reduction in the sintering temperature needed to obtain dense ceramics. Using the CSP, materials can be sintered in a short time using an appropriate amount of a liquid phase at temperatures < 300 °C under a few hundred MPa of uniaxial pressure. For these reasons, cold sintering is considered one of the most promising ways to obtain ceramic proton conductors in mild conditions. This review aims to collect novel insights into the application of the CSP with a focus on BCZY-type materials, highlighting the opportunities and challenges and giving a vision of future trends and perspectives.

Surface-enhanced Raman Scattering Biosensor by Combining Rare Earth Elements: Integration with Machine Learning Tools for Diosgenin and Tectorigenin Detection and Classification

Surface-enhanced Raman Scattering Biosensor by Combining Rare Earth Elements: Integration with Machine Learning Tools for Diosgenin and Tectorigenin Detection and Classification

Lanthanide conjugate Pr-MPO elicits anti-cancer activity by targeting lysosomal machinery and inducing zinc-dependent cataplerosis.

Acquired drug resistance is a major challenge in the management of cancer, which underscores the need for discovery and development of novel therapeutic strategies. We report here the mechanism of the anti-cancer activity of a small coordinate complex composed of the rare earth metal praseodymium (Pr) and mercaptopyridine oxide (MPO; pyrithione). Exposure of cancer cells to relatively low concentrations of the conjugate Pr-MPO (5 µM) significantly impairs cell survival in a p53-independent manner and irrespective of the drug resistant phenotype. Mechanistically, Pr-MPO-induced cell death is caspase-independent, not inhibitable by necrostatin, but associated with the appearance of autophagy markers. However, further analysis revealed incomplete autophagic flux, thus suggesting altered integrity of lysosomal machinery. Supporting the lysosomal targeting activity are data demonstrating increased lysosomal Ca2+ accumulation and alkalinization, which coincides with cytosolic acidification (drop in pHc from 7.75 to 7.00). In parallel, an increase in lysosomal activity of glycosidase alpha acid (GAA), involved in passive glycogen breakdown, correlates with rapid depletion of glucose stores upon Pr-MPO treatment. This is associated with swift cataplerosis of TCA cycle intermediates, loss of NAD+/NADH and increase in pyruvate dehydrogenase (PDH) activity to compensate for pyruvate loss. Addition of exogenous pyruvate rescued cell survival. Notably, lysosomal impairment and metabolic catastrophe triggered by Pr-MPO are suggestive of Zn2+-mediated cytotoxicity, which is confirmed by the ability of Zn2+ chelator TPEN to block Pr-MPO-mediated anti-tumor activity. Together, these results highlight the ability of the small molecule lanthanide conjugate to target the cells' waste clearing machinery as well as mitochondrial metabolism for Zn2+-mediated execution of cancer cells, which could have therapeutic potential against cancers with high metabolic activity.

Adsorption of rare earth ions from highly saline media by a pyridine-modified activated carbon sorbent

Adsorption of rare earth ions from highly saline media by a pyridine-modified activated carbon sorbent

Effect of Microalloying Rare-Earth Nd on Microstructure Evolution and Mechanical Property of Cu Alloy

Cu alloys have been widely used in the manufacture of liners because of their high density, good plasticity, and excellent thermal conductivity. In order to achieve excellent jet stability and penetration performance, it is necessary to further improve the mechanical properties of Cu-based liners. Nevertheless, the simultaneous enhancement of strength and ductility of the Cu alloys remains a huge challenge due to the strength–ductility trade-off phenomenon of metals/alloys. In this study, the microstructure evolution of rare earth Nd-modified Cu alloy and its effect on mechanical properties were investigated using OM, SEM, EBSD, and TEM techniques. The results show that the ultimate tensile strength (218 MPa) and elongation (50.7%) of sample 1 without Nd are the lowest. With increasing Nd content; the tensile strength and elongation of the samples increase; and the mechanical properties of sample 4 are the best, with a tensile strength of 278.6 MPa and elongation of 65.2%. In addition, with the increase in Nd content, not only is the grain size of the Cu-Nd alloy refined, but also the strength and plasticity are improved so that the strength–ductility trade-off phenomenon is improved. The strength improvement is mainly attributed to grain refinement strengthening, dispersion strengthening, and strain hardening. The increase in ductility is mainly related to the improvement of the microstructure heterogeneity by the Nd element.

Distribution, and mobility of rare earth elements in surface sediment of Gomishan Wetland

Rare earth elements (REEs) are emerging environmental contaminants that pose a threat to ecosystem health. Their accumulation in sediments and potential release into the water column can raise concerns. Understanding the factors influencing REE mobility is crucial. Furthermore, our knowledge of the risk and occurrence of REEs in wetland ecosystems is inadequate. This study investigated REE release from sediments under varying redox conditions (Eh). The different redox potential values were adjusted using a photoanode (Ti/TiO2) and a cathode (graphite). Also, to recognize the relationship between REEs and other parameters, Pearson correlation (PC) was employed. Results showed that increasing Eh initially enhanced REE mobility (until around 300 mV), followed by a decrease at higher Eh values. Among the studied REEs, lanthanum (La), cerium (Ce), and gadolinium (Gd) exhibited the highest release potential into water, with measured concentrations reaching 199.4, 93.1, and 31.2 µg/L, respectively. Moreover, according to several eco-geochemical risk assessment indices, the sediment of the study area was classified as minimal contamination. Statistical analyses revealed that Eh indirectly affects REE mobility by influencing linked changes in pH, salinity, and iron-manganese (Fe-Mn) chemistry, which in turn impacts REE solubility and release from sediments.

A Comparison Study on the Recovery of REEs from Red Mud by Sulfation Roasting–Water Leaching and Citric Acid Leaching

In this study, the recovery of rare earth elements (REEs) from red mud (bauxite residue) was explored through a combination of citric acid leaching and sulfation roasting–water leaching processes, introducing an innovative approach to the field. The research uniquely investigates the influence of citric acid on the leaching behavior of REEs and impurities in both untreated red mud and red mud subjected to sulfation roasting, providing a direct comparison of these methodologies. A novel aspect of this study is the evaluation of solvent extraction efficiency using DEHPA, highlighting the selective recovery of REEs over impurities from both citric acid and water-leaching solutions. Furthermore, a comprehensive phase analysis using X-ray diffraction (XRD) was conducted to track the transformations of minerals during the sulfation roasting process, an original contribution to the literature. The findings revealed that over 85% of REEs and major elements such as Fe, Al, Ca, and Ti dissolved in water after sulfation at 105 °C, while iron and titanium dissolution significantly decreased following roasting at 725 °C. Importantly, terbium, neodymium, and gadolinium extraction efficiencies were notably affected by roasting temperature. Citric acid leaching results demonstrated that the direct leaching of red mud leads to higher leaching efficiency than leaching it after the roasting process. Solvent extraction demonstrated lower terbium and neodymium recovery from citric acid solutions compared to water leaching solution. Finally, stripping experiments illustrated that 6M H2SO4 solution is capable of stripping more than 80% of rare earth elements, except terbium.

Enhanced optical and structural traits of irradiated lead borate glasses via Ce3+ and Dy3+ ions with studying Radiation shielding performance

Lead borate glass is the best radiation shielding glass when lead is in high concentration. However, it has low transparency after radiation exposure. Radiation decreases transparency due to chemical and physical changes in the glass matrix, such as creating or healing defects in the glass network. The addition of rare earth elements like cerium and dysprosium oxides to lead borate glasses can improve their transparency and durability as radiation shielding barriers. The newly manufactured glasses’ optical absorption, structural, and radiation shielding properties were measured. The optical characteristics of the generated samples were examined to determine the effect of the cerium/dysprosium ratio on the structural alterations, specifically in the presence of bridging oxygen (BO) and non-bridging oxygen (NBO). Incorporating Ce3+ results in peaks at 195 nm for borate units, 225 nm for Ce3+, and a broadened peak at 393 nm due to overlapping peaks for Ce3+ and Ce4+ in the UV region. By adding Dy, multiple peaks are observed at 825, 902, 1095, 1275, and 1684 nm, corresponding to the transition from 6H15/2 ground state to 6F5/2, 6F7/2, 6F9/2, 6F11/2, and 6H11/2. The samples were also tested before and after exposure to gamma irradiation from a 60Co source at a dose of 75 kGy to assess their stability against radiation. The energy gap value during irradiation shows decreased non-bridging oxygen. The energy gap difference before and after irradiation for the M4 sample shows higher NBO to BO conversion, reducing radiation damage and improving structural stability. Furthermore, X-ray photoelectron spectroscopy was utilized to get insight into the coordination chemistry of the created glass samples. The half-value layer (HVL), radiation protection efficiency (RPE), neutron removal cross-section (FRNCS), mean free path (MFP), mass attenuation coefficients (MAC), and effective atomic numbers (Zef) of the glassy structure were calculated theoretically to assess its radiation shielding qualities. The linear attenuation coefficient order for the prepared samples was M1 > M2 > M3 > M4. The FRNCS values were 0.090, 0.083, 0.081, and 0.079 cm−1 for samples M1, M2, M3, and M4, respectively.

Substantial trace metal input from the 2022 Hunga Tonga-Hunga Ha’apai eruption into the South Pacific

The January 2022 eruption of the Hunga Tonga-Hunga Ha’apai (HTHH) volcano discharged 2,900 teragrams of ejecta, most of which was deposited in the South Pacific Ocean. Here we investigate its impact on the biogeochemistry of the South Pacific Gyre (SPG) using samples collected during the GEOTRACES cruise GP21 in February-April 2022. Surface water neodymium isotopes and rare earth element compositions showed a marked volcanic impact in the western SPG, potentially extending to the eastern region. Increasing trace metal concentrations in surface waters and chlorophyll-a inventories in euphotic layers between the eastern and western SPG further suggest that the volcanic eruption supplied (micro)nutrients potentially stimulating a biological response. We estimate that the HTHH eruption released up to 0.16 kt of neodymium and 32 kt of iron into the SPG, which is comparable to the annual global dust-borne Nd flux and the annual dust-borne Fe flux to the entire SPG, respectively.

Tribological and Corrosion Properties of Al2O3@Y2O3-Reinforced Ni60A Composite Coatings Deposited Using Laser Cladding

Since rare earth oxides and hard ceramic particles improve coating quality, a novel Al2O3@Y2O3 core–shell structure was prepared. Then, Ni60A coatings with different amounts (2~6 wt.%) of Al2O3@Y2O3 core–shell structures were prepared using laser cladding technology on an H13 steel surface. To demonstrate the unique effect of the core–shell structure on the performance of the coatings, a set of controlled experiments was also conducted with different proportions of Al2O3-Y2O3 mechanically mixed powders. The effect of Al2O3@Y2O3 addition on the phase composition, element distribution, microstructure, wear, and corrosion resistance of the coatings was characterized and tested thoroughly. By comparing the forming quality, hardness, wear, and corrosion resistance of the different coatings, 2 wt.% was confirmed as the optimal concentration of Al2O3@Y2O3, and its corresponding friction coefficient was about 0.44. The wear rate was approximately 4.15 × 10−3 mm3·(N·m)−1, the self-corrosion potential was around −0.3659 V, and the self-corrosion current density was about 1.248 × 10−6 A·cm−2.

Structural order and disorder within novel antiferromagnetic RCrxGa3-yGey and R4Cr1-xGa12-yGey intermetallic compounds (R = Tb, Dy)

Single crystals of intermetallic phases RCrxGa3−yGey (R = Tb, Dy; x = 0.19–0.23, y = 0–0.4) and R4Cr1−xGa12−yGey (R = Tb, Dy; x = 0–0.13, y = 3–4) were grown from Ga flux ensuring the absence of magnetic impurities. The X-ray diffraction experiments revealed that the compounds belong to the family of filled AuCu3-type gallides. The compounds are formed upon the insertion of Cr atoms into E6 octahedral voids (E = Ga/Ge), which can occur in either disordered (RCrxGa3-yGey) or ordered (R4Cr1-xGa12-yGey) fashion. The unique feature of the obtained compounds is the strong correlation between the level of Ge doping and the Cr concentration in the phases, which allows one to control both the structural and magnetic ordering. At low Ge concentration, the cubic RCrxGa3-yGey phases form, which then experience tetragonal distortion upon the increase in the Ge content, and the cubic R4Cr1-xGa12-yGey 2×2×2 superstructures are formed at even higher Ge concentrations. The X-ray diffraction analysis also showed a presence of structural defects in the phases, which are caused by different size of empty E6 and filled CrE6 octahedra. Magnetic measurements of the single crystals of the cubic phases reveal antiferromagnetic ordering of the rare earth sublattice with the Neel temperatures decreasing upon Ge doping from 22 K for RCrxGa3 to 10 K for R4Cr1−xGa12−yGey. The Ge doping causes gradual decrease in the strength of antiferromagnetic R-R interactions ultimately leading to noncollinear magnetic structure in the superstructure R4Cr1−xGa12−yGey phases.

Efficient selective hydrogenation of phenylacetylene over Pd-based rare earth dual-atomic catalysts

Selective hydrogenation of phenylacetylene to styrene plays a vital role in fine chemical synthesis with palladium (Pd)-based catalysts as the active components and usually suffered from low selectivity due to over-hydrogenation and low stability through polymerization (c.a. green oil generation). In this work, we found that by confining the Pd atom within a Pd-Ln (Ln: rare earth elements, such as Y, Lu, etc. ) diatomic structure [diatomic catalyst (DAC)], the reaction performance of selective hydrogenation of phenylacetylene has been greatly promoted, in which 92% styrene selectivity has been determined at 100% phenylacetylene conversion. This would be attributed to the diatomic structure established, which was achieved by introducing Pd-Ln precursors and confirmed by high-angle annular dark-field scanning transmission electron microscopy (HAADF-STEM) and X-ray adsorption fine structure (XAFS) characterizations and it was demonstrated that slight electron transfer from Ln to the adjacent isolated Pd makes it slightly negatively charged and facilitated the styrene formation. Besides, a Langmuir-Hinshelwood model was established to describe the whole reaction mechanism. After a systematic kinetic investigation, it suggests that the C8H6* + H* elementary step is probably the kinetically relevant for the whole reaction and the surface of the catalyst is mainly covered by C8H6*. The energy relationship of each step along phenylacetylene hydrogenation was quantitatively described by means of parity fitting and gas isothermal adsorption, providing insights into the selective hydrogenation of phenylacetylene over 0.02%Pd-Ln/C (Ln = Y/Lu) catalysts and pave the way of catalytic design at the atomic level.

Opportunities and Constraints of the Adsorption of Rare Earth Elements onto Pyrolytic Carbon-Based Materials: A Mini-Review

Rare earth elements (REEs), comprising seventeen metallic elements, including lanthanides, scandium, and yttrium, are indispensable for modern technological industries due to their unique properties. However, their supply is critically risky for the European Union, with 95% of global production concentrated in China, Brazil, Vietnam, Russia, India, and Australia. This mini-review examines the adsorption of REEs onto pyrolytic carbon-based materials as a sustainable recovery method from secondary raw materials. The review covers different types of carbon-based adsorbents used in several research works, such as activated carbon, chars, and biochar, and discusses their adsorption mechanisms and influencing factors. Comparative analyses of adsorption capacities highlight the significance of surface area and functionalization in enhancing adsorption efficiency. Despite promising results, the variability in adsorption performance due to experimental conditions and the scarcity of real-world application studies are noticed. This review underscores the need for further research using real e-waste leachates to validate the practical applicability of pyrolytic carbon-based adsorbents for REEs’ recovery, aiming for an economically and environmentally sustainable solution.

Tri-axial magnetic alignment and magnetic anisotropies in misfit-layered calcium-based cobaltites doped with rare-earth ions

In this study, we introduce an original method for quantifying tri-axial magnetic anisotropy in [Ca2CoO3-δ]0.62CoO2, and its rare earth (RE)-doped variants, [(Ca1-xREx)2CoO3-δ]0.62CoO2, utilizing a modulated rotating magnetic field of 10 T. Our findings reveal a significant correlation between the magnetic anisotropy and local structure of RE ions, particularly bond lengths and coordination numbers, which influence the magnetization axes of these magnetically aligned powders. We introduce an analytical methodology employing linear equations to calculate the magnetic susceptibilities along distinct crystallographic axes, enabling the prediction of tri-axial magnetic anisotropies at elevated concentrations of Er ions. This research not only advances our understanding of magnetic anisotropy control but also paves the way for the successful fabrication of triaxially-aligned ceramics using magneto-science techniques.

Synthesis of Pt-Rare Earth Metal Alloys and Their Applications.

The alloying of platinum (Pt) with rare earth (RE) metals has emerged as a highly promising strategy for enhancing both the activity and stability of catalysts. Consequently, the development of methods for the controlled synthesis of Pt-RE alloys has received growing attention. This review comprehensively explores diverse synthesis methodologies for Pt-RE alloys, including physical metallurgy method, chemical reduction method, electrodeposition method, and dealloying method. Additionally, this review summaries the applications of Pt-RE alloys in various fields. By providing a critical analysis of existing literature and highlighting key challenges and future directions, this review aims to offer valuable insights and serve as a springboard for further advancements in the controlled synthesis and diverse applications of Pt-RE alloys.

Microalgae for the Extraction and Separation of Rare Earths: An STXM Study of Ce, Gd, and P

Microalgae for the Extraction and Separation of Rare Earths: An STXM Study of Ce, Gd, and P

Chemical durability of optical temperature sensors made of tellurite glass: Effect of the alumina concentration

Tellurite glass is an amorphous material commonly doped with rare earth ions for the development of optical temperature sensors. Considering the intrinsic properties of glasses, it is expected that these sensors could be used in acidic environments and withstand temperature changes. However, this has not been fully demonstrated since most of the literature is limited to demonstrate the sensor operation under normal conditions. Additionally, there is a lack of information regarding the chemical durability of these glasses and methods to improve it. In this work, a special tellurite glass composition was proposed for the development of optical temperature sensor. The effect of the alumina concentration on the structure, chemical durability and emission properties of the glasses was evaluated. Chemical durability was assessed by monitoring the weight loss of glass samples after immersion in hydrochloric acid solutions at room temperature, vegetable oil or air at 150 °C. The results indicate that the addition of alumina increases the chemical durability of the glass and improves its emission properties. It was found that the average temperature estimated by the optical sensor had a relative error of 1.3 % due to the degradation of the glass caused by remaining immersed in a 1 N HCl solution for 60 days.

Low-pressure superconductivity of Th-B-H ternary compounds: An insightful study of stable and metastable phases

The low-enthalpy structures of Th-B-H ternary compounds below 50 GPa are investigated by using an efficient framework that combines high-throughput screening, genetic algorithms, and first-principles calculations. Four thermodynamically stable hydrides (Th2BH11, Th2BH10, ThB2H10, and ThBH) and seven thermodynamically metastable hydrides (ThBH2, ThBH3, ThBH4, ThBH5, ThBH7, ThB2H4, and ThB3H3) are revealed. There are no stable thorium boron hydrides at ambient pressure. R3m-ThB2H10 and R3m-Th2BH11 are indirect bandgap semiconductors, while R3m-Th2BH10 and P6/mmm-ThBH show metallic nature. The relatively low λ values of R3m-Th2BH10 and P6/mmm-ThBH result in their Tc around 5.8 K and 0.1 K at 20 GPa, respectively. Two metastable phases, F4¯3m-ThBH5 and P63/mmc-ThBH7, exhibit excellent superconducting properties at low pressures. The values of Tc of F4¯3m-ThBH5 and P63/mmc-ThBH7 reach 46.9 K at 20 GPa and 40.0 K at 50 GPa, respectively. Our findings offer valuable insights for discovering and designing superconducting rare earth hydrides under low and even ambient pressures.

Clean Energy Challenges and Innovation Opportunities in Kazakhstan

Abstract Kazakhstan has pledged to transition to a low-carbon economy by implementing national policies and strategies that promote clean energy innovation. However, Kazakhstan is still falling short of its expected targets for energy transition, and there is a lack of knowledge regarding the country's challenges and opportunities for clean energy development. Towards this end, the current study identifies and assesses the enablers and barriers related to clean energy innovation in Kazakhstan. Using the combination of SWOT analysis, survey data from 41 experts and the DEMATEL decision support tool, we evaluated the key factors affecting Kazakhstan's clean energy innovation and their implications for energy transition. Assessment results show that the immature business environment, underpinned by technological, institutional, and socioeconomic factors, is perceived as a high-impact constraint for clean energy innovation and green finance deployment in Kazakhstan. Skilled labour shortages, high reliance on hydrocarbons and low retail energy prices are significant challenges to Kazakhstan's clean energy innovation. The low-profit margin and high investment risk in clean energy projects are identified as transition barriers in the power and energy-intensive industries. In contrast, Kazakhstan's endowments of resources critical for developing clean energy technologies (rare earth metals, uranium, gas) and the potential of low-carbon investments (e.g. carbon storage) are perceived as prominent enablers of clean energy innovation. Results are consistent across expert subgroups (academia, industry, NGOs, etc). Findings call for policy support to modern and attractive business environments, capacity, and human capital development. The findings can provide helpful insights for countries in Central Asia and beyond with similar socioeconomic structures that aim for a timely energy transition.