Heavy Rare Earth Research Articles

Provenance, chemical weathering, and sedimentary environment of the aquifer sediments: Implication for arsenic enrichment in groundwater

High arsenic (As) groundwater has been widely observed in the world, but the provenance, chemical weathering, and sedimentary environment of aquifer sediments hosting high As groundwater remain poorly understood. The geochemical and isotopic characteristics of high-resolution aquifer sediments were investigated to unravel the roles of provenance, chemical weathering, and sedimentary environment of the aquifer sediments. The average values of rare earth elements (REEs) showed the enrichment of light REEs and flat heavy REEs in the aquifer and the Yellow River sediments. The chemical index of alteration reflected incipient and moderate weathering (41 to 71). The δ13CSOM (−27.4‰ ± 4.3‰) and C/N values (8.1 ± 5.8) indicated aquatic environment of sedimentation. Shallow aquifer sediments mostly had relatively high ΣREEs contents and negative Eu anomalies, demonstrating that the aquifer sediments were mainly derived from the Yellow River (up to 94.3% ± 5%). Deep aquifer sediments had relatively low ΣREEs contents and positive Eu anomalies, which originated from the Yinshan Mountains (up to 72.2% ± 20.4%) principally with igneous and metamorphic rocks. Moreover, recycling of the Yellow River sediments from Northeastern Tibetan Plateau enhanced the silicate weathering and increased contents of Fe/Mn oxides and As. The δ13CSOM and C/N values evidenced that organisms of paleo-lake or paleo-Yellow River were responsible for abundant sedimentary organic matter. Concentrations of Fe, Mn, and As were high in shallow groundwater from the plain. The As enrichment in the shallow groundwater was jointly controlled by the provenance and chemical weathering of the aquifer sediments (14%), sedimentary environment (10%), reductive dissolution (35%) of Fe/Mn oxides, As desorption under elevated pH (20%), and competitive adsorption of HCO3- (21%). This study systematically reveals the roles of provenance, chemical weathering, and sedimentary environment of the aquifer sediments and highlights joint contributions of geochemical processes and geochemical conditions to As enrichment in groundwater.

Eocene crustal thickening in the Tethyan Himalaya: Insights from Barrovian metamorphism and granite geochemistry from the Ramba area

Magmatism, structures, and metamorphism in the Ramba dome of the Tethyan Himalaya were investigated to shed light on orogenic processes during the early stages of the India-Asia collision. Deformed granite dikes in the dome envelope yield zircon U-Pb ages of ca. 45 Ma. These Eocene granites have adakitic, Na-rich compositions (K2O/Na2O = 0.20−0.61), weak to no Eu anomaly, enrichment in Sr, depletion in heavy rare earth elements and Y, and low MgO and Mg# contents. These characteristics contrast with the Miocene potassic granites in the core of the dome and suggest that the Eocene adakites were derived from the high-pressure melting of crustal amphibolites in a thick crust. The mica schists of the dome envelope have an early foliation (S1) that is overprinted by upright folds (F2). Phase-equilibria modeling of garnet and staurolite mica schists suggests a Barrovian-type, prograde P-T evolution in association with S1, with peak conditions of 6.7−7.2 kbar/590−605 °C and 7.3−7.8 kbar/650−670 °C, respectively, which are typical of crustal thickening metamorphism. Monazites from S1-dominated staurolite mica schists yield metamorphic ages of ca. 51−49 Ma, while those from the late foliation (S2) that transposed S1 give younger ages of ca. 10 Ma. The integration of geochemical, structural, metamorphic, and geochronological data suggests that peak Barrovian D1 metamorphism and adakitic magmatism occurred in the Eocene in response to crustal thickening. The results provide critical constraints for addressing the crustal shortening deficit of the region.

Geology and Geochemical Characterization of Basement Rocks Around Burumburum Area North Central Basement Complex Nigeria

The geology and the geochemical characterization of rocks around Burumburum area north central basement complex of Nigeria was studied. Twelve (12) rocks samples were prepared for petrographic studies through a standard procedure while thirty (30) whole rocks samples were analyzed using X-ray Fluorescence (XRF) and Inductively Coupled Plasma Mass Spectrometry(ICP-MS). The result of the field investigation revealed that the study area is underlain by migmatites, gneisses, biotite microgranites, fine grained biotite granites, medium grained biotite granites, porphyritic biotite-hornblende granites, granodiorites, syenites, diorites, dolerites, quartzite, pegmatites and aplites. The geochemical characterizations of the granites, granodiorites, syenites based on Na<sub>2</sub>O/K<sub>2</sub>O versus SiO<sub>2</sub> showed acidic compositions while diorites and dolerites are intermediate to basic compositions. The granites, granodiorites, syenites, diorites and dolerites are generally peraluminous (ASI>1.1) to metaluminous (ASI≤1). The granitic rocks, diorites, dolerites and syenites plotted mainly in shoshonite series while the granodiorites occur in High-K calc-alkaline fields. The granitic rocks, syenites, diorite and dolerites based on A/CNK versus SiO<sub>2</sub> are of I-type while granodiorites are of S-type. The multi-elements discrimination trends for granites, granodiorites, syenites, diorites and dolerites revealed relative enrichment in Large Ion Lithophile Elements (LILE: Ba, La, Rb, and Th and depletion in High Field Strength Elements (HFSE: Nb, P, Ti and Sr) which indicates crustal contamination of magma. The enrichment in the light rare earth element (LREE) relative to heavy rare earth element (HREE) for granodiorites, fine grained biotite granites, medium grained biotite granites (except medium grained biotite granites S12 and S14 with positive Eu), porphyritic biotite-hornblende granites and syenites with negative Eu anomaly suggest moderate to high degree of fractionation. The enrichment in light rare earth element (LREE) for diorites and dolerites relative to moderate to flat HREE with weak negative Eu anomaly indicates low degree of fractionation. The Y+Nb vs Rb, Y vs Nb, Ta + Yb vs Rb and Yb vs Ta tectonic discrimination diagram revealed that granites and syenites plotted mainly within volcanic arc granite, syn-collisional granite and in the within plate granites fields, the granodiorites clearly plotted in the within the plate granites field. The tectonic ternary molecular proportions MgO – FeOt – Al<sub>2</sub>O<sub>3 </sub>revealed that dolerites and diorites plotted mainly in the spreading center island field.

Mineral Chemistry and Chronology Investigation of Uraninite in the Jinguanchong Uranium Deposit in Eastern Hunan Province and the Implications for Geological Significance.

Jinguanchong deposit, a part of the Mingyuefeng ore field in eastern Hunan Province, China, is a typical perigranitic uranium deposit (a subtype of granite-related deposit) discovered recently with considerable uranium mineralization. Herein, uraninite, the primary ore mineral in the deposit, was investigated via scanning electron microscopy and electron probe microanalysis. Additionally, laser ablation-inductively coupled plasma-mass spectrometry was used for the first time to determine the in situ U-Pb age and the rare-earth element characteristics of uraninite. Uraninite mainly comprises UO2, CaO, and PbO with a low ThO2 content. Uraninite exhibits a low total content of rare-earth elements with a distinct fractionation between light and heavy rare-earth elements while displaying a negative Eu anomaly. The presence of major elements and rare-earth elements in uraninite suggests its formation within a hydrothermal environment at moderate to low temperatures below 350 °C, thereby classifying the Jinguanchong deposit as a typical hydrothermal vein-type uranium deposit. The uranium metallogenic age is determined to be 93.8 ± 1.4 Ma, falling within the midlate Cretaceous period. This age corresponds to the Mesozoic lithospheric extension and thinning events (approximately 85-95 Ma) in South China, suggesting that the formation of the Jinguanchong uranium deposit might be associated with the tectonic dynamics of lithospheric extension and thinning.

Discussion of the W-Sn-REE Metallogenic Background in the Nanling Region of South China: Evidence from Satellite Gravity and Magnetic Data

The Nanling region is located at the intersection of the Yangtze Block and Cathaysia Block and is characterized by complex geological and tectonic processes, as well as distinct W-Sn-REE mineralization. Despite extensive research on the mineralization of W-Sn and REE deposits in the Nanling region, the factors impacting the distribution pattern of eastern tungsten and western tin deposits, as well as the mechanism of REE enrichment in the parent rocks, remain uncertain. Deep structural and tectonic variability plays a crucial role in the formation of mineral deposits in the upper crust. Information on deep structural and tectonic variability is contained in the Moho depth, Curie depth, effective elastic thickness, lithospheric density, and thermal structure derived from the processing and inversion of satellite gravity and magnetic data. In this paper, we comprehensively analyse satellite gravity and magnetic data from the Nanling region, integrating the processing and inversion results with the tectonic evolution of this region and relevant geological information. It is hypothesized that the Chenzhou–Linwu fault serves as a channel for mineral and thermal transfer in the Sn ore aggregation zone, facilitating the material transport from the deep mantle to the surface and ultimately leading to the formation of Sn-enriched granite. The collection area of tungsten ore is more weakly associated with the Chenzhou–Linwu fault, and through deep heat transfer, tungsten components are primarily concentrated in the Earth’s crust to produce W-enriched granite. The primary source of REE enrichment in the parent rocks associated with REE mineralization is predominantly derived from the felsic crust, and the rapid intrusion of deep magma resulting from the subduction and retraction of the Palaeo-Pacific Plate is a contributing factor to the contrasting enrichment of light and heavy rare-earth elements. Mineral crystalline differentiation is relatively high, leading to the formation of ore-forming parent rocks with high heavy rare-earth element contents.

Petrogenesis and tectonic implications of the Bloubergstrand basaltic andesites, Tygerberg Formation, Malmesbury Group, Pan-African Saldania Belt, southwestern Africa

Abstract The Bloubergstrand Member, consisting of mafic to intermediate tuffs and flows within the Tygerberg Formation of the Malmesbury Group, is a crucial but understudied component of the western Saldania Belt in southwestern Africa. With a U-Pb zircon age of 555 ± 5 Ma, these volcanic rocks provide valuable insights into the origins and, more broadly, the tectonic setting of the Saldania Belt during the final stages of Malmesbury Group sedimentation in the context of the construction of southwestern Gondwana at approximately 560 to 540 Ma. The Bloubergstrand Member amygdaloidal volcanic rocks vary from basaltic andesitic to andesitic and have experienced varying degrees of alteration. The volcanic rocks are enriched in the large ion lithophile elements (LILE) relative to the high field strength elements (HFSE). When normalised to primitive mantle values, they show enrichment in Cs, Rb, K and Pb and mild enrichment in Th, U, Zr and Hf, with the light rare earth elements (LREE) enriched relative to the heavy rare earth elements (HREE). They are depleted in Ba, Nb, Ta, Sr, Eu, P and Ti. εNd(t) values are mildly negative ranging from -3.60 to -2.39, and Nd TDM model ages range from 1.4 to 1.7 Ga. Initial 87Sr/86Sr ratios vary from 0.70478 to 0.70620, with one higher value of 0.72270, the latter likely due to extensive alteration. The Bloubergstrand Member volcanic rocks exhibit characteristics suggesting their origin from partial melting of lithospheric to transitional asthenospheric upper mantle, influenced by sediment-derived melts and variable degrees of crustal contamination. With continental arc basalt compositions and similarities to shoshonites, the samples reflect variable degrees of partial melting and source heterogeneities. Fractional crystallisation of pyroxenes, hornblende, and plagioclase contributes to compositional variability. Erupting in a continental arc margin, likely part of the Arachania block of the Kalahari craton, separated during the Tonian break-up of Rodinia, the volcanics were associated with the Marmora basin formed by eastward-directed subduction below the western Kaapvaal Craton margin. Extruded in a distal position relative to the Cuchilla Dionisio Arc in present-day southern Brazil and Uruguay, these volcanic rocks preceded the closure of the southern Marmora basin. The mantle melting, possibly a result of slab roll-back, break-off, ridge subduction, or a combination, served as a precursor to the lower crustal heating that generated the granitic magmas of the Cape Granite Suite.

Effect of Calcination Atmosphere on the Acid Leaching Recovery of Rare Earth Elements in Coal-Byproducts

ABSTRACT Thermal treatment of coal byproducts has been shown to improve leaching characteristics of rare earth elements (REEs) in bituminous coal sources due to its influence on the associated minerals. This study investigated the impact of the calcination atmosphere on REE leaching behavior in different density fractions of Baker and Fire Clay seam coarse refuse sources using a thermogravimetric analyzer to create an oxidizing or reducing atmosphere at a desired temperature for 2 h. The effect on leaching characteristics was evaluated using 1.2 M sulfuric acid at 75°C for 5 h at 1% w/v solid concentration. Rare earth element (REE) recovery for the 2.2 specific gravity (SG) sink fraction improved by approximately 15 absolute percentage points at 1000°C relative to the 600°C calcined sample in an inert atmosphere and equilibrated within 10 min from the start of the test. Contrarily, thermal treatment at 1000°C under oxidizing atmosphere significantly reduced the REE recovery due to sintering of the clays, which limited access to the RE minerals for leaching. In general, thermal treatment of heavier fractions in both atmospheres significantly improved the light REE (LREE) recovery while the increase in heavy REE (HREE) recovery was relatively less. As common clay minerals in the coal sources, kaolinite and illite samples were tested under the same conditions and using a digital scanning calorimeter. The findings confirmed that the improvement observed in REE leaching through thermal treatment at 600°C was due to decarbonization for the lighter density fractions and dehydroxylation of clays.

Utility and influence mechanism of densification modulation on grain boundary diffusion in NdFeB magnets

Grain boundary diffusion technology is pivotal in the preparation of high-performance NdFeB magnets. This study investigates the factors that affect the efficiency of grain boundary diffusion, starting from the properties of the diffusion matrix. Through the adjustment of the sintering process, we effectively prepared magnets with varied densities that serve as the matrix for grain boundary diffusion with TbHx diffusion. The mobility characteristics of the Nd-rich phase during the densification stage are leveraged to ensure a more extensive distribution of heavy rare earth elements within the magnets. According to the experimental results, the increase in coercivity of low-density magnets after diffusion is significantly greater than that of relatively high-density magnets. The coercivity values measured are 805.32 kA/m for low-density magnets and 470.3 kA/m for high-density magnets. Additionally, grain boundary diffusion notably enhances the density of initial low-density magnets, addressing the issue of low density during the sintering stage. Before the diffusion treatment, the Nd-rich phases primarily concentrate at the triangular grain boundaries, resulting in an increased number of cavity defects in the magnets. These cavity defects contain atoms in a higher energy state, making them more prone to transition. Consequently, the diffusion activation energy at the void defects is lower than the intracrystalline diffusion activation energy, accelerating atom diffusion. The presence of larger cavities also provides more space for atom migration, thereby promoting the diffusion process. After the diffusion treatment, the proportion of bulk Nd-rich phases significantly decreases, and they infiltrate between the grains to fill the cavity defects, forming continuous fine grain boundaries. Based on these observations, the study aims to explore how to utilize this information to develop an efficient technique for grain boundary diffusion.

Geochemistry of Rare Earth Elements in Pahang River Sediment, Malaysia

Rare earth elements (REE) are a set of 17 chemically similar metallic elements including 15 lanthanides, scandium and yttrium. The current status of REE as a global strategic commodity has encouraged the identification of REE ore deposits. This research is carried out to identify the mining feasibility of fluvial sediment REE and to understand the sediment's physical and chemical characteristics and effects on the geochemical behaviour of REE in the longest river of Peninsular Malaysia namely Pahang River. Surface sediment samples were collected along Pahang River (n=44) in approximately 10 km distance intervals. The sediment samples were analyzed using XRF to determine the major oxide content. Meanwhile, REE content in the sediment samples was extracted using the Total Digestion method and analysed using ICP-MS. The results show the average value of ΣREE at surface sediments of the Pahang River is 42.58 ppm and can be considered too low to be economically mined. Each area shows higher fractionation of light REE than heavy REE with negative europium anomalies, suggesting sediments in this area were derived from felsic rocks. The concentration of REE in Pahang River surface sediments was controlled by the porosity and organic matter as showed by the correlation of ΣREE with porosity (R2=0.65) and organic matter content (R2=0.71). In conclusion, this research's findings are generally useful for further REE mineral exploration and fluvial sediment environmental monitoring.

Comprehensively improved magnetic performance of Nd-Fe-B magnets with high-efficiency grain boundary diffusion of heavy rare earth

Comprehensively improved magnetic performance Nd-Fe-B magnets with extremely limited amount of Heavy Rare Earth (HRE) elements are obtained to meet the increasingly demanding applications. In this work, Tb–Co thin film with uniform distribution, flat surface and strong adhesion is successfully prepared by magnetron sputtering, and the effects of Tb–Co film thickness on the magnetic properties are investigated. The magnets with optimal magnetic properties are achieved when the film thickness is about 3.5 μm, the coercivity of 1284.81 kA/m, the remanence of 1.48 T, and the maximum magnetic energy product of 437.32 kJ/m3, compared with the original magnets, enhancing by 47.9 %, 0.4 % and 5.7 %, respectively, so the magnetic properties have been comprehensively improved using little amount of HRE and Co elements. HRTEM and EPMA results revealed that Tb-rich shell distributed around the Nd2Fe14B grain. The mechanisms of the remanence and coercivity simultaneous enhancement of Nd-Fe-B magnets is elaborated in detail. Besides, the diffusion of Tb–Co thin film can enhance thermal stability of the magnets.

Study on magnetic properties and demagnetization process of the c-plane in the grain boundary diffusion magnet

Grain boundary diffusion (GBD) can effectively increase the coercivity of sintered Nd-Fe-B magnets. Tb is deposited in the specific areas of the c-plane rather than the entire c-plane to reduce the amount of heavy rare earth elements. In this work, we investigate the magnetic properties and demagnetization process of the c-plane using experimentation and micromagnetic simulation. The c-plane is divided into the center area without Tb deposition and the edge area with Tb deposition. According to the results of the experiment and micromagnetic simulation, it has been found that diffusion on the edge area can decrease the amount of Tb by 58% and increase the contribution of Tb to coercivity (ΔHcj/wt.% Tb) to 20.55 kOe/wt.%. Compared to the other areas on the c-plane, diffusing on the edge area offers the vast majority of Hcj for the GBD and has the highest ΔHcj/wt.% Tb. Diffusing a small amount of Tb onto the center area can supplement the remaining Hcj. Micromagnetic simulation and Magneto-optical Kerr microscopy are used to study the differences in magnetic properties among different areas on the c-plane by simulating the demagnetization process. Because the edge area is more likely to be demagnetized than the center area, the diffusion of Tb in the edge area can significantly strengthen Hcj.

Aromatic and magnetic properties in a series of heavy rare earth-doped Ge6 cluster anions.

A series of pentagonal bipyramidal anionic germanium clusters doped with heavy rare earth elements, (RE = Gd, Tb, Dy, Ho, Er, Tm, Yb, and Lu), have been identified at the PBE0/def2-TZVP level using density functional theory (DFT). Our findings reveal that the centrally doped pentagonal ring structure demonstrates enhanced stability and heightened aromaticity due to its uniform bonding characteristics and a larger charge transfer region. Through natural population analysis and spin density diagrams, we observed a monotonic decrease in the magnetic moment from Gd to Yb. This is attributed to the decreasing number of unpaired electrons in the 4f orbitals of the heavy rare earth atoms. Interestingly, the system doped with Er atoms showed lower stability and anti-aromaticity, likely due to the involvement of the 4f orbitals in bonding. Conversely, the systems doped with Gd and Tb atoms stood out for their high magnetism and stability, making them potential building blocks for rare earth-doped semiconductor materials.

Rare earth element distribution patterns in Lakes Huron, Erie, and Ontario

Rare earth elements (REE) are increasingly used in industrial applications, consumer electronics and green technologies, but their baseline concentrations and distribution patterns in the North American Great Lakes remain poorly understood. Here, we report dissolved REE concentrations in > 70 surface water samples from Lakes Huron, Erie, and Ontario (2021 and 2022) and assess their spatial distribution patterns and governing biogeochemical controls. Dissolved (<0.22 µm-filtered) REE concentrations were spatially heterogeneous (up to 3 orders-of-magnitude) across the lakes and did not systematically increase upstream-to-downstream through the basin. Nearshore-to-offshore decreases in dissolved REE levels were observed for all lakes and appeared the result of REE adsorption to colloids and subsequent sedimentation. Combined with enrichment of light over heavy REE, particularly in samples closer to shore, our data suggests that riverine input is a major pathway by which REE are loaded to the lakes. Finally, we used normalization and pattern-filling to assess REE anomalies in the lake surface waters. Anomalies for Gd (>20 % across the lakes) were notably higher than those of the other REE but varied significantly spatially, and also showed enrichment nearshore, particularly near urban centers and in Lake Ontario. This work provides new surveillance data to further develop our understanding of REE dynamics in the Great Lakes.

Petrography, geochemistry and detrital zircon U–Pb dating of the Pliocene‐Pleistocene Dupi Tila Formation from the Lalmai Anticline, Bengal Basin: Regional tectonic implications

The Bengal Basin is a well‐known foreland basin that archives the tectonic evolution of the Himalayan and Indo‐Burman Ranges (IBR). The Dupi Tila Formation is the youngest among the stratigraphic successions of the Bengal Basin, which witnessed the last phase of the Himalayan uplift. However, there is still controversy regarding sediment provenances since the Himalayan and IBR are in the late Neogene exhumation stage. In this study, the petrographical and geochemical compositions of the Dupi Tila sandstones from the Lalmai Anticline of the Bengal Basin are examined to infer the source rocks, tectonic settings, palaeoclimate and weathering intensity in provenance areas. The detrital modes and geochemical discriminations, as well as Chondrite‐normalized rare earth elements patterns with enrichment in light rare earth elements and nearly flat heavy rare earth elements and negative Eu anomalies (average Eu/Eu* = 0.77) indicate dominantly felsic source rocks. The geochemical data also suggest that these source rocks in provenance areas were influenced by weak to moderate chemical weathering (chemical index of alteration: 65.64–75.62) and multiple recycling under warm and humid to semi‐humid climatic conditions. The detrital zircon ages show three dominant peaks at ca. 100, 500 and 1000 Ma with minor 1700 Ma. The amount of young zircon grains (&lt;120 Ma) is noticeably higher (~18%) in this Lalmai outcrop compared to the Dupi Tila samples from the Sylhet Trough and Chittagong‐Tripura Fold Belt. Results from integrated zircon geochronology and geochemistry indicate that the detritus are likely derived from a recycled orogen provenance related mainly to active continental margin setting with subordinate influence from passive setting. Therefore, the regionally extensive Himalayan Orogen appears to be the primary sediment source, with additional mixing from the IBR and recycled sediments originating from the Gangdese batholith of the Trans‐Himalaya.

Theoretical Calculations and Experimental Investigation of Separation of Dy3+, Er3+, Tm3+ and Yb3+ by Cascade Extraction in TOGDA–Kerosene/Hydrochloric Acid System

The hot spot extraction agent N,N,N′,N′-tetraoctyl-3-oxoglutaramide (TODGA) has the advantages of novelty, high efficiency and environmental protection in the separation of rare earths by tandem extraction. In this paper, the characteristic parameters for the separation of dysprosium, erbium, thulium and ytterbium ions in the TOGDA–kerosene/hydrochloric acid system for tandem extraction were calculated. Using a 10% TODGA–kerosene/5 mol·L−1 hydrochloric acid extraction system, the mixture containing Dy3+ 0.258 mol·L−1, Er3+ 0.252 mol·L−1, Tm3+ 0.248 mol·L−1 and Yb3+ 0.242 mol·L−1 can be separated by three separation steps, and four products of Dy3+, Er3+, Tm3+ and Yb3+ can be obtained. The purity of the four products was 99.80%, 99.20%, 99.70% and 99.70%, and the yields were 99.03%, 98.97%, 97.88% and 96.98%, in order. In this paper, the reasons were analyzed for the differences in the ability of the TODGA system to extract heavy rare earth ions (REEs) in terms of density functionality, complex structure and bond valence model. These will provide more basic data and guidance for the industrial application of TODGA.

Effects of Clipping Intensity on the Physiology of Dicranopteris pedata and Its Interroot Soil in the Rare-Earth-Mining Area in Southern China

Clipping is crucial during phytoremediation. However, research into the effects of clipping intensity on the physiology of Dicranopteris pedata (D. pedata) and its interroot soil in the rare-earth-mining area in southern China is lacking. A clipping experiment was conducted to verify the phytoremediation effect of D. pedata. The physiology of D. pedata, such as biomass, antioxidant enzymes, chlorophyll, and rare-earth elements (REEs), were determined after clipping. And the microbial community diversity and soil enzyme activities in the interroot soil of D. pedata were investigated. The phytoremediation efficiency was determined at the end of the experiment. The results showed that the compensatory growth effect of D. pedata was stronger with increasing clipping intensity. There was no significant difference in the α diversity of interroot soil microorganisms of D. pedata at different clipping intensities, but β diversity analysis showed that the clipping treatment group deviated from the control group. Only urease activity decreased among the interroot soil enzymes in D. pedata after clipping, while the soil catalase and sucrase were less responsive to clipping. The REEs accumulated by D. pedata were dominated by light REEs in the aboveground part of the plant, while the amounts of light and heavy rare-earth elements accumulated in the underground part of the plant were similar. The phytoextraction of REEs gradually increased with increasing clipping intensity. It was concluded that 100% clipping once a year is the most appropriate when considering D. pedata’s phytoremediation potential and soil system. The time it takes for 100% clipping of D. pedata to reduce the soil TREEs (total rare-earth elements), LREEs (light rare-earth elements), and HREEs (heavy rare-earth elements) to below-average soil REE concentration in China was estimated to be 25.54 years, 19.56 years, and 65.43 years, respectively, which was significantly lower than that for other clipping intensities and the control group. It is concluded that clipping D. pedata is an effective way to promote phytoextraction efficiency in the southern rare-earth-mining areas. The soil can still support the resumption of D. pedata growth after high-intensity clipping.

Mineralogy and element geochemistry of the Bayan Obo (China) carbonatite dykes: Implications for REE mineralization

The Bayan Obo deposit in China is the world's largest rare earth element (REE) deposit. However, its genesis remains highly debated. It is considered to have a close genetic association with carbonatites because of the presence of nearby carbonatite dykes and the geochemical similarities between these dykes and the orebody. However, the evolution of these dykes and associated REE mineralization remain poorly understood, hindering the origin interpretation of the deposit. This study provides new insights into the petrography, mineralogy, and major- and trace-element geochemistry of these carbonatite dykes and rock-forming minerals to reconstruct the magmatic evolution and REE enrichment of the deposit. The dykes evolved from dolomite- to calcite-dominated (i.e., calcite and fenitized calcite) carbonatites, and their REE content remarkably increased, with the latter developing strong REE mineralization. The dolomites and minor calcites within the dolomite carbonatites exhibit a steep negative slope with high light REE (LREE) enrichment and heavy REE (HREE) depletion, similar to the whole rock. In contrast, the calcites from the calcite-dominated carbonatites exhibit flat REE patterns with HREE enrichment. Combined with previous isotopic data and our petrology, mineralogy, and geochemistry study, we propose that these rocks are derived directly from the low-degree melting of the underlying mantle source. REE mineralization may be related to the progressive crystallization of rock-forming calcites of calcite-dominated carbonatites. Monazite, bastnäsite, parisite, and huanghoite are the dominant REE minerals and exhibit intimate associations with barite and alkaline silicate minerals such as aegirine, biotite, K-feldspar, and albite. This assemblage indicates that the REE were primarily transported via REE–sulfate and REE–alkali complexes, with the latter favoring HREE, and the precipitation of alkaline silicate minerals destabilized these REE complexes, facilitating REE mineralization.

Calcium–magnesium–aluminum‐silicate melt viscosities influenced by lanthanides, yttrium, and zirconium

AbstractLanthanides (Ln2O3) and elements like Zr and Y find application in the highest temperature‐resistant thermal and/or environmental barrier coatings. Such coatings are routinely exposed to silicate particles (e.g., sand, dust, volcanic ash), leading to chemical reactions that degrade the coating. The dissolution of 13.5 wt.% Ln2O3 into a calcium–magnesium–aluminum‐silicate (CMAS) melt leads to a viscosity reduction for the light lanthanides, while viscosity increases toward heavier lanthanides. For Gd, Y, and Zr, various amounts up to 13.5 wt.% (Gd2O3, Y2O3, ZrO2) were added to the CMAS melt, showing a tendency of increased viscosity for low concentrations (2.5‐3 wt.%) and a decreasing viscosity for higher values of the added component.

Optical Chemosensors Synthesis and Appplication for Trace Level Metal Ions Detection in Aqueous Media: A Review.

In recent years, the development of optical chemosensors for the sensitive and selective detection of trace level metal ions in aqueous media has garnered significant attention within the scientific community. This review article provides a comprehensive overview of the synthesis strategies and applications of optical chemosensors dedicated to the detection of metal ions at low concentrations in water-based environments. The discussion encompasses a wide range of metal ions, including but not limited to heavy metals, transition metals, and rare earth elements, emphasizing their significance in environmental monitoring, industrial processes, and biological systems. The review explores into the synthesis methodologies employed for designing optical chemosensors, discovering diverse materials like organic dyes, nanoparticles, polymers, and hybrid materials. Special attention is given to the design principles that enable the selective recognition of specific metal ions, highlighting the role of ligand chemistry, coordination interactions, and structural modifications.Furthermore, the article thoroughly surveys the analytical performance of optical chemosensors in terms of sensitivity, selectivity, response time, and detection limits. Real-world applications, including water quality assessment, environmental monitoring, and biomedical diagnostics, are extensively covered to underscore the practical relevance of these sensing platforms. Additionally, the review sheds light on emerging trends, challenges, and future prospects in the field, providing insights into potential advancements and innovations. By synthesizing the current state of knowledge on optical chemosensors for trace level metal ions detection. The collective information presented herein not only offers a comprehensive understanding of the existing technologies but also inspires future research endeavors to address the evolving demands in the realm of trace metal ion detection.

Identification of yttrium oxide-specific peptides for future recycling of rare earth elements from electronic scrap.

Yttrium is a heavy rare earth element (REE) that acquires remarkable characteristics when it is in oxide form and doped with other REEs. Owing to these characteristics Y2 O3 can be used in the manufacture of several products. However, a supply deficit of this mineral is expected in the coming years, contributing to its price fluctuation. Thus, developing an efficient, cost-effective, and eco-friendly process to recover Y2 O3 from secondary sources has become necessary. In this study, we used phage surface display to screen peptides with high specificity for Y2 O3 particles. After three rounds of enrichment, a phage expressing the peptide TRTGCHVPRCNTLS (DM39) from the random pVIII phage peptide library Cys4 was found to bind specifically to Y2 O3 , being 531.6-fold more efficient than the wild-type phage. The phage DM39 contains two arginines in the polar side chains, which may have contributed to the interaction between the mineral targets. Immunofluorescence assays identified that the peptide's affinity was strong for Y2 O3 and negligible to LaPO4 :Ce3+ ,Tb3+ . The identification of a peptide with high specificity and affinity for Y2 O3 provides a potentially new strategic approach to recycle this type of material from secondary sources, especially from electronic scrap.