Rare Earth Research Articles

Factors affecting the geochemistry of rare earth elements in soils in tropical rain and montane forests in Sri Lanka across an elevation gradient

Factors affecting the geochemistry of rare earth elements in soils in tropical rain and montane forests in Sri Lanka across an elevation gradient

Preparation of TA-O-MoS2/PES mixed matrix ultrafiltration membrane for rare earth wastewater treatment

The trade-off between permeability and selectivity, along with the issue of membrane fouling, has constrained the widespread application of ultrafiltration (UF) membranes in recycling rare earth wastewater. Here, we present the incorporation of tannic acid (TA) modified molybdenum disulfide oxide (O-MoS2) as a functional enhancer to fabricate polyethersulfone (PES) based mixed matrix membranes through a nonsolvent induced phase separation (NIPS) approach. Compared to the unmodified PES membrane, the integration of TA-O-MoS2 significantly improves the hydrophilicity, porosity in the mixed matrix membrane. By altering the concentration of TA-O-MoS2, the TA-O-MoS2/PES UF membrane achieves enhanced hydrophilicity and charge properties, resulting in a remarkable improvement in separation performance. Specifically, the optimized membrane M2 (TA-O-MoS2 addition of 0.1 wt%) exhibits a water flux of 140.98 Lm−2h−1bar−1 and a PEG 20000 rejection rate of 91.00 %, representing increases of 180 % and 120 % over the control PES membrane, respectively. Notably, membrane M2 effectively retains 91.31 % of macromolecular organic compounds in rare earth wastewater, while permitting nearly complete passage of inorganic salts, for instance CaCl2 (3.26 %) and MgSO4 (4.84 %). Moreover, the TA-O-MoS2/PES membrane demonstrates robust antifouling properties and exceptional durability, indicating its significant potential for efficient treatment and resource recovery in rare earth wastewater.

Defect induced persistence photoconductivity in spray pyrolyzed ZnO thin films: Impact of Sm3+doping

The persistent photoconductivity of the rare earth ion doped ZnO is an emerging field. The present work focuses on the effect of samarium (Sm3+) ion doping on the persistence photo response behaviour ZnO host matrix. The Zn1-xSmxO (x = 0.0 to 0.10) thin films were deposited on chemically cleaned glass substrates using spray pyrolysis technique. The films showed polycrystalline nature and hexagonal wurtzite structure without any impurity peaks. The Zn0.93Sm0.07O films showed maximum crystallite size of 24.2 nm and minimum dislocation density. The gradual change in the thickness of the fibrous nature was observed with the addition of Sm3+ ions into ZnO lattice. Energy dispersive analysis of x-ray and X-ray photoelectron spectroscopy confirmed the presence of elements and its oxidation states in the deposited film respectively. The area under the curve of deconvoluted photoluminescence spectra of deposits confirmed the decrease in the various defect percentage with increase in the doping concentration of Sm3+ ions. The photoluminescence spectra of Zn0.93Sm0.07O films showed maximum near band edge emission and minimum defects. The Zn0.93Sm0.07O films showed higher carrier concentration of 1 × 1017 cm−3, mobility 32 cm2/Vs and lower resistivity of 1 × 102 Ω cm due to improved film quality. The Zn0.93Sm0.07O films exhibited the current value under dark and ultraviolet light illumination was in the range of 10−6 A and 10−4 A respectively. The maximum photocurrent was noticed at 375 nm which corresponds to the bandgap of the deposited films. The Zn0.93Sm0.07O films showed faster photo response (5 s and 131 s of response and recovery time) due to the presence of minimum trap states. Hence the Zn0.93Sm0.07O films can be used in the fabrication of light dependent resistors and ultraviolet sensors.

The crystal structure of R3Fe0.1Ga1.6S7 chalcogenides (R – La, Ce, Pr and Tb)

The paper reports the study of the crystal structure of chalcogenides of the composition R3Fe0.1Ga1.6S7 (R = La, Ce, Pr and Tb) as promising materials predicted to possess interesting nonlinear optical and electrical properties. Samples of stoichiometric composition were synthesized by co-melting the elements in quartz containers evacuated to a residual pressure of 10–2 Pa at the maximum synthesis temperature of 1100 °C. The crystal structure of the chalcogenides La3Fe0.1Ga1.6S7 {a = 10.1884(6) Å, c = 6.0515(4) Å}, Ce3Fe0.1Ga1.6S7 {a = 10.0864(4) Å, c = 6.0440(3) Å}, Pr3Fe0.1Ga1.6S7 {a = 9.9853(3) Å, c = 6.0648(2) Å} and Tb3Fe0.1Ga1.6S7 {a = 9.6692(7) Å, c = 6.0799(5) Å} was studied by X-ray powder method. It was determined that the structure of the synthesized phases belongs to the hexagonal symmetry (La3CuSiS7 structure type; space group P63). The structure of the complex chalcogenides (A), (B), (C) and (D) is based on the R3Ga1.67S7 sulfides (R = La, Ce, Pr, and Tb) by substituting gallium atoms in the 2a sites with atoms of statistical mixture M1{0.57(2) Ga + 0.10(2) Fe}, M2{0.56(1) Ga + 0.10(2) Fe}, M3 {0.61(8) Ga + 0.09(1) Fe} and M4 {0.57(2) Ga + 0.10(2) Fe}, respectively. Rare earth atoms are localized in the 6c sites and center sulfur atoms to form trigonal prisms with an additional atom [R 3S13S21S3]. Atoms of statistical mixtures M1, M2, M3, M4 are localized in the 2a sites forming [M 6S2] octahedra. Ga atoms in the 2b sites are surrounded by four sulfur atoms [Ga 3S11S3].

New stable rare earth Ti-based semiconductor pyrochlore oxides for low-cost energy applications

New stable rare earth Ti-based semiconductor pyrochlore oxides for low-cost energy applications

Mechanisms of roasting for improving rare earth element leaching from coal gangue

ABSTRACT Coal resources represent an important potential source for the future extraction of rare earth elements (REEs). This study, combining microscopic characterization techniques and experimental analysis, investigates the occurrence characteristics of REEs in coal gangue and the roasting activation mechanisms. The study reveals that phosphate minerals are the primary carriers of REEs, and sequential chemical extraction results further confirm the close association between REEs and phosphate minerals. Roasting at around 600°C facilitates the release of REEs from organic matter and clay minerals like kaolinite, significantly improving leaching efficiency. Under leaching conditions of 20 g/L, 50°C, 0.5 M HCl, and 1000 RPM, the leaching of REEs can reach approximately 80%. However, when the roasting temperature exceeds 1000°C, the formation of mullite leads to mineral surface sintering, reducing the recovery of REEs. This study emphasizes the importance of optimizing roasting conditions and understanding mineral phase changes to maximize REEs recovery, which is crucial for sustainable resource management and environmental remediation.

A Review of the Physical, Optical and Photoluminescence Properties of Rare Earth Ions Doped Glasses

Doping glasses with rare-earth ions have garnered significant attention among researchers worldwide. This interest stems from the widespread utilization of rare-earth ions to enhance the optical characteristics of host glasses and exploit the unique spectroscopic properties arising from their optical transitions in the intra-4f shell. Thus, this study reviewed the exceptional potential of rare-earth ion-doped glasses (REIs) in various applications such as solid-state lasers, photonic devices, communication optical fibers, and white light emission. Various methods for the fabrication of glass such as direct melt quenching, sol-gel, ion exchange, sputtering and co-doping techniques were reviewed extensively. The Specific focus was on the physical, optical and photoluminescence properties of glasses produced from glass formers co-doped with rare earth ions. The investigation centers on the comprehensive current applicability of REI-doped glasses. The review concludes based on the physical, optical and photoluminescence properties of rare earth ion-doped glasses that they are extremely useful in photonics, lasers, biomedical and optical communication applications.

Effect of yttrium doping on the properties of Nickel-Iron multiphase heterostructures at high current conditions

Transition metal selenides hold great promise for producing clean hydrogen energy from water electrolysis, but it is not clear how transition metal elements can improve the stability of catalyst performance at high current levels. This work presents the use of nickel foam (NF) as a hydrothermal selenium substrate for yttria-doped multiphase bifunctional catalysts (Y-MSex/NF; M = Ni, Fe). Under high current circumstances, the linked structure of nanosheets and nanoscale microspheres created by hydrothermal selenium enhanced the catalytic reaction area and demonstrated exceptional performance. The overpotentials of the catalysts for the hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) were 350 mV and 340 mV, respectively, at a current density of 1000 mA cm−2(j1000). Moreover, stable operation in 1.0 M potassium hydroxide at a current density of 100 mA cm−2for 50 h further demonstrated the good electrocatalytic stability. Demonstrate the potential of selenides doped with the rare earth element yttrium for total water decomposition applications.

Late Ordovician Bentonites From the Southern Ordos Basin: Response to the Subduction of the Proto‐Tethys Ocean

ABSTRACTThe connection between the Ordovician bentonites on the southern margin of the Ordos Basin and the Early Palaeozoic volcanic rocks of the North Qinling Orogenic Belt is crucial for understanding the subduction and collisional closure of the Shangdan Ocean during the Early Palaeozoic. This paper investigates zircon U–Pb ages, geochemistry and Lu–Hf isotopic compositions of zircons in the Upper Ordovician Zhaolaoyu Formation bentonites located on the southern margin of the Ordos Basin. U–Pb dating of zircon indicates a coeval age of 453.3 ± 1.4 Ma (MSWD = 0.99), which represents the crystallisation age during the Late Ordovician Katian stage. The bentonites exhibit higher SiO2 (57.94–77.95 wt.%) and Al2O3 (9.21–14.33 wt.%), classifying them within the low‐potassium alkali basalt to medium‐potassium calc‐alkaline series. The parent rock of the bentonites is likely intermediate to felsic volcanic rocks. The rare earth element partitioning curves of the bentonites are right‐dipping, with a more pronounced negative Eu anomaly (δEu = 0.48–0.67). The zircons in the bentonites yield two‐stage model ages ranging from 546 to 956 Ma, along with εHf(t) values between 5.56 and 13.55. These results indicate that the bentonites are products of volcanic arc magma formed in a subduction–collision environment. The interbedded bentonites in the Upper Ordovician limestones of the southern margin of the Ordos Basin may be associated with the northward subduction of the Shangdan Oceanic crust, reflecting the subduction and consumption of the Proto‐Tethys Ocean along the southern margin of the North China Block.

Effect of Addition of Rare Earth Metal (Ce) on the Microstructure, Mechanical Properties and Corrosion Behavior of NiTi Alloys

Effect of Addition of Rare Earth Metal (Ce) on the Microstructure, Mechanical Properties and Corrosion Behavior of NiTi Alloys

Explore on the Mechanism of Action between Al2O3–SiO2 Refractory Materials and Rare Earth High Carbon Heavy Rail Steel

Explore on the Mechanism of Action between Al2O3–SiO2 Refractory Materials and Rare Earth High Carbon Heavy Rail Steel

Sulfuric Acid Leaching Recovery of Rare Earth Elements from Wizów’s Phosphogypsum in Poland

Rare earth elements (REEs) are considered vital raw materials for the economy and are on the European Union’s list of critical raw materials (CRMs). Europe is mainly dependent on REE imports. This dependence could be reduced if locally available primary or secondary resources would be processed. In Poland, there are, for instance, over 5 million metric tons of phosphogypsum (PG), a fine powdery byproduct from the fertilizer industry, available near the former Wizów Chemical Plant near Bolesławiec. This material that is considered a waste in Poland contains significant amounts of REEs that could theoretically be recovered and contribute to Europe’s economy. This work is the first systematic analysis of REE leaching studies with sulfuric acid and PG from Wizów. Process parameters such as temperature, particle size, concentration of the leaching solution, and the addition of oxidant and reductant agents were tested to determine the most efficient process. Ultimately, a leaching efficiency of 99% was obtained. Lanthanum exhibited the highest leaching efficiency at almost 100%, followed by Yttrium, Neodymium, Terbium, and Dysprosium. The results of the laboratory experiments are promising and suggest that larger pilot or commercial experiments can be performed next.

Potential for the Recovery of Selected Metals and Critical Raw Materials from Slags from Polymineral Zn–Pb Ore Metallurgy—Part I

Slags from the Silesia–Cracow Upland (Poland), including ten historical slags (deposited in waste dumps) and four contemporary slags (from current production), were examined to compare their chemical and mineralogical properties as well as to assess their potential for the recovery of selected metals and critical raw materials. The historical slags associated with the smelting of polymetallic ores originating from Mississippi Valley-type (MVT) deposits consisted primarily of gypsum. The contemporary slags, obtained from industrial waste rich in zinc and lead, were predominantly spinels (magnesium-aluminate and ferric) that exhibited higher iron content (up to 46.6 wt% of Fe2O3) compared to the historical slags (up to 26.1 wt% of Fe2O3). The zinc content was similar for both the slag types (3.5 wt% Zn). The average titanium and arsenic contents in the old and contemporary slags were at the same level as well, with 0.21 wt% (Ti) and 0.13 wt% (As), respectively. The contemporary slags contained higher levels of critical raw materials, such as cobalt, nickel, copper, and manganese, compared to the historical slags. Rare earth elements (REEs) were also more abundant in the contemporary slags, with an average content of 212 ppm, while the historical slags averaged 124 ppm. These findings underscore the potential for recovering valuable metals and critical raw materials from such slags, presenting opportunities for resource optimisation and environmental management.

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.