Heavy Rare Earth Research Articles

Design and Computational Validation of γ-Ray Shielding Effectiveness in Heavy Metal/Rare Earth Oxide-Natural Rubber Composites.

This study involved the preparation of natural rubber-based composites incorporating varying proportions of heavy metals and rare earth oxides (Sm2O3, Ta2O5, and Bi2O3). The investigation analyzed several parameters of the samples, including mass attenuation coefficients (general, photoelectric absorption, and scattering), linear attenuation coefficients (μ), half-value layers (HVLs), tenth-value layers (TVLs), mean free paths (MFPs), and radiation protection efficiencies (RPEs), utilizing the Monte Carlo simulation software Geant4 and the WinXCom database across a gamma-ray energy spectrum of 40-150 keV. The study also compared the computational discrepancies among these measurements. Compared to rubber composites doped with single-component fillers, multi-component mixed shielding materials significantly mitigate the shielding deficiencies observed with single-component materials, thereby broadening the γ-ray energy spectrum for which the composites provide effective shielding. Subsequently, the simulation outcomes were juxtaposed with experimental data derived from a 133Ba (80 keV) γ-source. The findings reveal that the simulated results align closely with the experimental observations. When compared to the WinXCom database, the Geant4 software demonstrates superior accuracy in deriving radiation shielding parameters and notably enhances experimental efficiency.

Anthropogenic impact of rare earth elements on groundwater and surface water in the watershed of the largest freshwater lake in China

Limited knowledge exists regarding the potential risks associated with anthropogenic release of rare earth elements (REEs) in the environment. This study aimed to investigate REE signatures in the watershed Poyang Lake, the largest freshwater lake in China. Samples of surface water, wastewater, and groundwater were collected from five rivers discharging into the lake. Results revealed wastewater from wastewater treatment plants contained total REE concentrations from 231 to 904 μg/L, exceeding those found in surface water (0.4 to 1.3 μg/L) and groundwater (0.5 to 416 μg/L). Samples with elevated REE were found in Ca-Mg-Cl/SO4 type waters and exhibited an 18OD deviation from local meteoric water line. Wastewater exhibited a higher positive Gd anomaly compared to surface water and groundwater, attributed to anthropogenic input of Gd (Gdanth). The determined Gdanth concentration ranged from 0.04 to 0.21 μg/L, and from 0.06 to 0.37 μg/L, accounting for 4 % to 21 % and 49 % to 84 % of total Gd concentrations in groundwater and surface water, respectively. Gdanth concentration in wastewater (0.19 to 0.43 μg/L) remained constant in effluent after wastewater treatment. Surface water displayed relatively complex normalized REE patterns influenced by anthropogenic activities and natural processes (weathering and complexation), while groundwater exhibited heavy REEs enrichment, due to carbonate solution complexation. Additionally, Gdanth concentration showed a positive correlation with ΣREE, Pb, Ni, and Co concentrations in groundwater, indicating a good pollution tracing potential. Health risk assessment using the hazard quotient (HQ) suggested higher HQGd values in groundwater compared to surface water. Residents in the eastern part of Poyang Lake were found to face higher risks associated with Gd in groundwater compared to the western part, with infants and children at greater risk than adult males and females. These findings offer valuable insights into environmental behavior and health risks of REEs in aquatic systems impacted by human activities.

Fluid Inclusion, Rare Earth Element Geochemistry, and Isotopic (O and S) Characteristics of the Ardakan Barite Deposit, Yazd Province, Iran

The stratabound barite mineralization occurs in the Ardakan deposit as patches and veins in the dolomites and limestones of the Middle Triassic Shotori Formation. Rare-earth element (REE) geochemistry, O and S isotopes, and fluid inclusion data were used to identify the mode of barite formation. Barite is associated with subordinate fluorite and quartz and, to a lesser extent, with sphalerite, malachite, chrysocolla, and iron and manganese oxide-hydroxides. Barite contains a very low ∑REE concentration (14.80–19.59 ppm) and is enriched in light rare-earth elements (LREEs) relative to heavy rare-earth elements (HREEs). The low ∑REE content and the Ce/La ratio (4.0–6.5) indicate a hydrothermal (terrestrial) origin of the barite. Similar to barite, the ∑REE content in fluorite is low (0.14–6.52 ppm) and suggests a sedimentary setting. The Tb/Ca versus Tb/La diagram also indicates a hydrothermal origin of fluorite. The δ34S values in the barite (+27.9 to +32.4‰) indicate that the sulfur most likely originates from evaporites and/or connate waters from the Late Precambrian to the Lower Cambrian. The δ18O values (+15.9 to +18.1‰) in the barite show that the oxygen originated either from Late Precambrian–Lower Cambrian evaporites or from basinal brines with slightly higher δ18O values than the evaporites. The salinity and homogenization temperature ranges of the aqueous fluid inclusions in barite, fluorite, and quartz (0.88–16.89 wt% NaCl equivalent and 90–270 °C, respectively) reveal that the mineralizing fluids were formed from basinal brines with the participation of heated meteoric water. From this, it is concluded that the Ardakan barite deposit was formed by the meeting of heated, ascending sulfate-bearing meteoric water and cooler, Ba-bearing connate water trapped in the overlying Middle Triassic dolomites and limestones. The Ardakan deposit belongs to the structure-related class and the unconformity-related subclass of barite deposits.

Mineralogical and geochemical characteristics of mudstones from the Lower Cretaceous Prosopis Formation in the Bongor basin, Chad: Implications for provenance, paleoenvironment and organic matter enrichment

The Cretaceous greenhouse represents the largest global warming event since the Phanerozoic, significantly affecting the provenance, weathering, regional climate, and paleoenvironment of lake basins globally. During the period of global warming, the control of regional paleoenvironment over organic matter enrichment is still unclear. The Lower Cretaceous Prosopis Formation in the Bongor Basin features thick lacustrine organic-rich mudstones as major effective hydrocarbon source rocks with excellent hydrocarbon potential in the basin. However, the provenance, paleoclimate, paleoenvironment and mechanism of organic matter accumulation in this location have not yet been systematically studied. In this study, 22 dark gray mudstone samples were collected from three cored wells. Clay mineralogy, along with organic and inorganic elemental geochemical analyses were jointly carried out to determine the characteristics of the provenance, paleoclimate and paleoenvironment as well as the major controlling factors for organic matter enrichment. The results imply that the Prosopis Formation mudstones are mainly composed of clay minerals such as illite, kaolinite, chlorite, and illite/smectite mixed layers (I/S). Organic geochemistry indicated that all the studied mudstones reached the standard of good to excellent source rocks (the total organic carbon content ranged from 1.27% to 7.41%). Inorganic elemental geochemistry is characterized by high enrichment of Fe, Mg, P, Mn, Ti, Na, Ca, V, Co, Cu, Sr, Ba and B relative to UCC and PAAS, whereas rare earth elements (REEs) show enrichment of light rare earth elements (LREEs) and a deficiency of heavy rare earth elements (HREEs) relative to chondrite. The source composition of the mudstones is predominantly intermediate-felsic igneous rocks that have not undergone sediment recycling. The parent rocks experienced weak to moderate weathering, corresponding to semiarid paleoclimatic conditions of transitional nature. The organic-rich mudstones were deposited in fresh to brackish waters with paleoredox conditions ranging from weakly oxic to anoxic semi-deep to deep lake environments having relatively low initial productivity. Comprehensive study indicates that paleoredox and paleoclimate are important parameters affecting the enrichment of organic matter in lake basins during global warming. The aridification of climate is one of the most important reasons for the high input and efficient preservation of organic matter. The relatively semiarid climate both increased the supply of terrigenous nutrients to the lake basins and provided a driving force for the increase in salinity, thereby providing better sources and preservation conditions for organic matter.

Post-collisional reworking of juvenile mafic lower crust for the petrogenesis of late Triassic adakitic rocks in the East Kunlun Orogen

The East Kunlun Orogen (EKO), a major component of the Greater Tibetan Plateau, provides an excellent natural laboratory to investigate the tectonic evolution of the Paleo-Tethys Ocean (also known as the A'nyemaqen Ocean in the EKO). We present a combined study of in situ zircon UPb ages and LuHf isotopic compositions, and whole-rock major and trace element and Sr–Nd–Hf isotopic compositions of the post-collisional Xiangjia granodiorite at the eastern end of the EKO. Zircon UPb dating indicates that the Xiangjia granodiorites were emplaced at 225.0–217.1 Ma. Relict zircon cores yield ages of 267.5–239.5 Ma. These granodiorites are calc-alkaline to high-K calc-alkaline and metaluminous to weakly peraluminous, enriched in large-ion lithophile elements and light rare earth elements, and depleted in high field strength elements (e.g., Nb and Ta) and heavy rare earth elements. They yield trace element characteristics that are typical of adakitic rocks, including high Sr (493–590 ppm) and low Yb (0.74–1.12 ppm) and Y (8.83–12.24 ppm) contents, high Sr/Y (40.47–63.64) and (La/Yb)N (11.81–30.91) ratios, and positive Eu anomalies. The UPb ages and Hf isotopic compositions of the relict zircon cores and whole-rock SrNd isotopic compositions of the Xiangjia adakitic rocks are similar to those of the mafic arc magmatic rocks formed during the subduction of the Paleo-Tethys Ocean, suggesting they originated from the reworking of juvenile mafic lower crust. Phase equilibrium modelling suggests that the contemporaneous adakitic rocks from Xiangjia and other areas in the EKO are likely the products of partial melting of the juvenile mafic arc rocks under granulite-facies conditions at 10–11 kbar and 934–951 °C, possibly related to slab break-off in a post-collisional setting.

Geochronology, Geochemical Characterization and Tectonic Background of Volcanic Rocks of the Longjiang Formation in the Lengjimanda Plate Area, Middle Da Hinggan Mountains

The Lengjimanda plate is situated in the middle section of the Da Hinggan mountains, in the eastern section of the Tianshan Xingmeng orogenic belt. To determine the formation age of the volcanic rocks in the Longjiang formation in this area, to explore their origin and tectonic background, and to reconstruct the geodynamic evolution of the region, this study conducted petrological, zircon U–Pb geochronological, geochemical, and isotopic analyses of the volcanic rocks in the Longjiang formation. The Longjiang formation’s volcanic rocks are primarily composed of trachyandesite, trachyte trachydacite, and andesite, which are intermediate basic volcanic rocks. They are enriched in large-ion lithophile elements, are depleted in high-field-strength elements, are significantly fractionated between light and heavy rare earth elements, and exhibit a moderate negative Eu anomaly in most samples. The results of the LA–ICP–MS zircon U–Pb dating indicate that the volcanic rocks in this group were formed in the Early Cretaceous period at 129.1 ± 0.82 Ma. The zircon εHf(t) ranges from +1.13 to +43.77, the tDM2 ranges from +655 to +1427 Ma, the initial Sr ratio (87Sr/86Sr)i ranges from 0.7030 to 0.7036, and the εNd(t) ranges from +2.1 to +6.6. Based on the geochemical compositions and isotopic characteristics of the rocks, the initial magma of the volcanic rocks in the Longjiang formation originated from the partial melting of basaltic crustal materials, with a source material inferred to be depleted mantle-derived young crustal. These rocks were formed in a superimposed post-collisional and continental arc environment, possibly associated with the Mongol-Okhotsk Ocean closure and the oblique subduction of the Pacific plate. This study addresses a research gap regarding the volcanic rocks of the Longjiang formation in this area. Its findings can be applied to exploration and prospecting in the region.

Fish 3D Locomotion app: a user-friendly computer application package for automatic data calculation and endpoint extraction for novel tank behavior in fish.

This paper introduces the Fish 3D Locomotion app (F3LA), a Python-based, Graphical User Interface (GUI)-equipped tool designed to automate behavioral endpoint extraction in zebrafish locomotion assays. Building on our previous work, which utilized a specialized aquatic tank with a mirror and a single camera for fish movement tracking in three dimensions, F3LA significantly enhances data processing efficiency. Its accuracy was tested by reanalyzing and comprehensively comparing the calculated data with the previously published data from prior publications. From the comparison results, 90% of endpoints showed a similar statistical difference result. These minor differences were due to the different starting points for the dataset and updated calculation formulas that are implemented in F3LA. In addition, shoaling area or shoaling volume calculations are also included in F3LA as a new feature that can serve as sensitive indicators of social cohesion, group dynamics, or stress responses, offering insights into neuropsychological conditions or the effects of pharmacological interventions. Furthermore, F3LA offers a marked improvement over manual operations, being at least five times faster, while maintaining consistent accuracy as it reduces human-induced errors, ensuring a higher degree of reliability in the results. Finally, the potency of F3LA was tested to evaluate the toxicities of 14 rare earth elements (REEs) to the adult zebrafish behaviors. Based on the results, our findings suggested that each tested REE altered fish behaviors in different patterns and magnitudes to each other. However, among the tested light rare earth elements (LREEs), neodymium was demonstrated to cause more relatively severe behavior alterations than other LREEs, indicated by the statistically higher value of entropy (0.2695 ± 0.04977 (mean with a standard deviation)) than the control group (0.2352 ± 0.05896). Meanwhile, in terms of heavy rare earth elements (HREEs), erbium seemed to lead to more distinct behavior toxicities than other HREEs, which was shown by the statistically lower level of fractal dimension (2.022 ± 0.3412) than the untreated group (2.255 ± 0.1661). Taken together, F3LA's development marks a significant advance in high-throughput toxicological and pharmacological assessments in zebrafish, leveraging three-dimensional locomotion data for a more comprehensive analysis of fish behavior performance, providing a significant contribution to research in various fields.

Impact of particle size and associated minerals on rare earth desorption and incorporation mechanisms in a South American ion-adsorption clay

This research delves into the intricate nexus of particle size, mineralogical composition, surface attributes, elemental mapping, and rare earth element (REE) adsorption mechanisms within an ion-adsorption clay sample from South America. The investigation entails the fractionation of the ion-adsorption clay into three size categories: S1 (< 0.25 mm), S2 (0.25–0.5 mm), and S3 (0.5–2 mm). Each fraction undergoes meticulous characterization to unveil its elemental composition, mineralogical composition, surface area, morphological characteristics, elemental mapping, and the mechanisms governing REE incorporation. The results indicate that S1 has 31% physiosorbed, 8% chemisorbed, and 61% mineralized REEs, while S2 has 40% physiosorbed, 5% chemisorbed, and 55% mineralized REEs, and S3 has 24% physiosorbed, 5% chemisorbed, and 71% mineralized REEs. The physisorbed REEs are attributed to the presence of kaolinite, conducive to mostly physisorption. In terms of grain size and REE content/type relationship, the results show that REE content decreases with increasing grain size; however, there is not a clear trend in terms of REE occurrence modes with grain size. Heavy rare earth elements (HREEs) are discernibly favored in adsorption over light rare earth elements (LREEs). This preference is underpinned by the weathering processes that led to the formation of ion-adsorption clay, which facilitated the transport and accumulation of HREEs. Notably, the ion-adsorption clay encompasses a substantial content of mineralized REEs, necessitating more demanding extraction methodologies, such as acid baking followed by water leaching if complete extraction of all REEs is desired. Among the desorbable REEs, physisorption dominates, encompassing over 80% of the total. Chemisorbed REEs exhibit versatility in association with various minerals, encompassing kaolinite, quartz, and goethite. In essence, this study unveils the intricate interplay between particle dimensions, mineralogical constitution, surface attributes, and REE adsorption modes within this ion-adsorption clay sample. The ion-adsorption clay in this study contains a significant portion of mineralized REEs that cannot be extracted using the mild conditions typically employed for the desorption process. Additionally, the REE concentration in this ion-adsorption clay is notably higher than the average found in clay deposits worldwide, reaching levels comparable to those of regolith deposits in China, which are a major global source of REEs. This remarkable concentration of REEs, along with the unique modes of their occurrence in this deposit, presents a significant interest to the scientific community.

Evidence for isotopically light Fe mobility under oxidising conditions in subduction zone fluids: A record of Monviso meta-serpentinites, Western Alps

The isotopically light Fe signature of arc magmas relative to mid-oceanic ridge basalts (MORB) is expected to be related to the redox state of their source. This implies a link between Fe mobility and redox variations across subduction zones. Here we address slab chemical variations during prograde metamorphism through a comprehensive geochemical study, including major, trace elements and Fe stable isotope (δ56Fe) analyses, of meta-serpentinites composing the eclogitic meta-ophiolite of the Monviso massif (Western Alps, Italy). These rocks partly preserve mantle related geochemical heterogeneities, as supported by negative correlations between fluid immobile elements (High Field Strong Elements) and LREE/HREE (Light – Heavy Rare Earth Elements) ratios. They are however characterized by large Cs enrichments relative to U or alkali elements suggesting that abyssal fluid mobile elements signature was overprinted by subduction related processes. Meta-serpentinites display large δ56Fe variations, from -0.20 ± 0.05 ‰ to +0.09 ± 0.03 ‰. Mineral separate analyses of olivine bearing veins show low Δ56Fe between olivine and magnetite (∼ 0.4 ‰), which according to Fe isotope thermometry correspond to high temperature equilibration, estimated between 530 and 550 °C, compatible with Monviso metamorphic climax (520–570 °C and 2.6–2.7 GPa). These results, in combination with geochemical modelling, confirm a reset of δ56Fe signature of abyssal serpentinites during prograde metamorphism in subduction zones. The bulk rock δ56Fe values of Monviso meta-serpentinites are negatively correlated with their Fe3+/∑Fe and As concentrations (a redox-sensitive and fluid mobile element). These correlations can be attributed to a metasomatism by external fluids derived from slab serpentinites during subduction. It also concords with the oxygen fugacity (fO2) record in meta-serpentinites, with meta-serpentinites equilibrated at high fO2 displaying the lowest δ56Fe values while samples equilibrated at low fO2 display mantle like δ56Fe signatures. These results highlight that oxidising conditions during serpentinite dehydration are likely to boost isotopically light Fe mobility in slab derived fluids.

Rare Earth Element Binding and Recovery by a Beta Roll-Forming RTX Domain.

The Block V of the RTX domain of the adenylate cyclase protein from Bordetella pertussis is disordered, and upon binding eight calcium ions, it folds into a beta roll domain with a C-terminal capping group. Due to their similar ionic radii and coordination geometries, trivalent lanthanide ions have been used to probe and identify calcium-binding sites in many proteins. Here, we report using a FRET-based assay that the RTX domain can bind rare earth elements (REEs) with higher affinities than calcium. The apparent disassociation constants for lanthanide ions ranged from 20 to 75 μM, which are an order of magnitude higher than the affinity for calcium, with a higher selectivity toward heavy REEs over light REEs. Most proteins release bound ions at mildly acidic conditions (pH 5-6), and the high affinity REE-binding lanmodulin protein can bind 3-4 REE ions at pH as low as ∼2.5. Circular dichroism (CD) spectra of the RTX domain demonstrate pH-induced folding of the beta roll domain in the absence of ions, indicating that protonation of key amino acids enables structure formation in low pH solutions. The beta roll domain coordinates up to four ions in extreme pH conditions (pH < 1), as determined by equilibrium ultrafiltration experiments. Finally, to demonstrate a potential application of the RTX domain, REE ions (Nd3+ and Dy3+) were recovered from other non-REEs (Fe2+ and Co2+) in a NdFeB magnet simulant solution (at pH 6).

Characterization of Rare Earth Elements in Cassiterite-Associated Minerals in Bangka-Belitung Islands, Indonesia

Rare earth elements (REEs) are crucial to numerous industries of high-technology as raw materials. The growth of a long-term relationship between REE supply and demand to develop hi-tech industries is becoming tight in the world market, while the mineral supply chain is being distorted by COVID-19. The availability of information and data regarding the REE resource potential and characteristics are interesting research subjects to examine its economic value as alternative sources. This research aims to provide basic information about the existence and characteristics of REEs in cassiterite-associated minerals located in Bangka and Belitung Islands. Fifty-one samples consisting of primary deposits, placer deposits, concentrates, and tailings were collected from the southern Bangka and Belitung region. The samples were analyzed using microscope, x-ray diffraction (XRD), scanning electron microscopy (SEM), electron probe micro-analysis (EPMA), and inductively coupled plasma mass spectrometry (ICP-MS). The results show that the REE-bearing minerals comprised monazite and xenotime. Monazite, the most dominant REE-bearing mineral, contains light REEs (Ce-dominant), while xenotime contains heavy REE (Y-dominant). The results of SEM with energy-dispersive spectroscopy show that monazite contains other LREE (La and Nd), and xenotime also contains other HREE (Dy and Yb). Moreover, zircon and ilmenite can be considered as economical cassiterite-associated minerals that have other mineral inclusion, but have no REE contain.

How do seasonal, significant events, and policies affect China's REE export prices? Based on deep learning perspective

This paper aims to accurately predict China's rare earth export prices and reveal the impact of variables such as seasonality, significant events, finance, and supply and demand on rare earth price volatility. Daily datasets of light and heavy rare earths from 2011 to 2023 were used, and the Tree-structured Parzen Estimator-Temporal Fusion Transformer model was employed to predict rare earth prices. Complete Ensemble Empirical Mode Decomposition with Adaptive Noise and partial dependence plots were used to reveal the factors affecting price volatility. The following conclusions were drawn: (1) The Tree-structured Parzen Estimator-Temporal Fusion Transformer deep learning model can provide more accurate rare earth price prediction information; (2) Light rare earth prices are more susceptible to cyclical influences, while heavy rare earth prices are more affected by significant events. The outbreak of COVID-19 has had a long-term impact on both light and heavy rare earth prices; (3) The fluctuations in heavy rare earth prices are mainly influenced by financial factors, while the fluctuations in light rare earth prices are influenced by multiple factors such as finance, supply and demand, and macroeconomics; (4) An increase in resource tax rates may lead to a decrease in rare earth prices, while an increase in restrictions on rare earth mining may lead to an increase in rare earth prices.

What are the different biomolecules involved in the selective recovery of REEs from mining wastewater using FeNPs synthesized from two plant extracts?

Extracting rare earth elements (REEs) from wastewater is crucial for saving the environment, sustainable use of natural resources and economic growth. Reported here is a simple, low cost and one-step synthesis of Fe nanoparticles (FeNPs) based on two plant extracts having the ability to recover REEs. The synthesis of FeNPs using Excoecaria cochinchinensis leaves extract (Ec-FeNPs) exhibited high selectivity for heavy rare earth due to unique biomolecules, achieving separation coefficients (Kd) of 3.16 × 103–4.04 × 106 mL/g and recovery efficiencies ranging from 71.7 to 100 %. Conversely, the synthesis of FeNPs using Pinus massoniana lamb extract (PML-FeNPs) revealed poorer REE recovery efficiencies of 7.2–86.7 %. To understand the differences between Ec-FeNPs and PML-FeNPs in terms of selectivity and efficiency, LC-QTOF-MS served to analyze the biomolecules differences of two plant extracts. In addition, various types of characterization were carried out to identify the different functional groups encapsulated on the surface of FeNPs. These results reveal the source of the difference in the selectivity of Ec-FeNPs and PML-FeNPs for REEs. Furthermore, during DFT calculations, it was found that biomolecules with varying affinities for the surface of FeNPs interact with each other, leading to the formation of structures that exhibit high reactivity towards REEs. Finally, incorporating Spearman correlation analysis demonstrates that the selective removal efficiency of REEs was closely linked to surface complexation, ion exchange, and electrostatic adsorption. Consequently, this work strongly highlights the potential for the practical application of novel adsorbents in this field.

Indigenous microbial influence on REE enrichment and fractionation in South China weathering crusts: Insights from experimental simulations

The activity of microorganism plays an important role on the enrichment, migration and fractionation of rare earth elements (REEs) in the supergene environment. To investigate the characteristics of indigenous microorganisms on the enrichment and fractionation of REEs, we studied the adsorption efficiencies of REEs by 30 indigenous microbial strains that were isolated and cultured from the weathering profile of a regolith-hosted REE deposit in South China. Most microbial strains exhibited high adsorption efficiencies for REEs, ranging from 2.3 to 42.9 mg g−1. Notably, the taxonomic classification of microorganisms significantly influenced the adsorption selectivity. Gram-positive bacteria exhibited a pronounced enrichment of the heavy REEs, while gram-negative bacteria showed no obvious adsorption preference. The tetrad effects were observed in REE adsorption patterns of gram-negative bacteria and fungi; however, fungi demonstrated a much higher affinity for light and medium REEs. Chemically modified microbial cells were employed to investigate the adsorption mechanism, revealing that distinct functional groups of microbial cells corresponded to the adsorption preference of microorganisms towards REE. Carboxyl and phosphate groups contributed to a relatively high adsorption capacity for light REEs and heavy REEs, respectively. The findings of our study suggest that the distinct composition of microbial groups may exert a significant influence on the biogeochemical cycle of REE in weathering profiles.

Features of Distribution of Rare-Earth Elements in Coals of the Far East

For the first time, the distribution of rare earth elements (REE) has been studied in detail for a number of coal facilities (30 deposits, 650 samples of coal and 210 samples of carbonaceous rocks). The ubiquitous presence of elevated concentrations of REE in coals has been noted. The REE mineral cluster in coals includes the association: ash content of coals – SiO2 – K2O – Al2o3 – TiO2 – Sc – Y – Dy – Ho – Er – Tm – Yb – Lu, and the association La – Ce – Pr – Nd – Sm – Eu – Gd – Tb. The presence of these elements of the mineral part of the coals is preferably in the composition of phosphate minerals – monazite and apatite (according to electron microscopy with microanalysis, the correlation of REE with P2o5). The content of individual REE in humic acids isolated from coals and fractions of coals of different densities has been studied. The specific role of organic matter(s) in the concentration of REE, their presence in the humus component of S and in low-ash coals is shown. Selective accumulation (fractionation) of heavy REE by organic matter has been experimentally established for the first time. Two genetic types of REE mineralization have been identified in coals: mainly terrigenous (hydrogenic) and tufogenic. The increased concentrations of REE in coals are due to the influence of the petrofund. The deposits were ranked according to the degree of prospects for REE based on an assessment of the resource potential of associated REE in the coals of the studied brown coal deposits. REE raw materials (lanthanides in coal ash) differ significantly from traditional types of rare earths ores by an incomparably large relative amount of heavy REE (on average 3–4 times), sometimes reaching 46% of the total REE content. Thus, coal ash is a unique non–traditional source of heavy lanthanides – more rare, valuable and expensive. The coals of the studied deposits should be considered as associated raw materials for rare earths.

Fate and potential ecological risk of rare earth elements in 3000-year reclaimed soil chronosequences

The introduction of anthropogenic inputs into natural systems may lead to enduring alterations in the innate characteristics of Rare Earth Elements (REEs). Against this backdrop, the evolutionary processes and environmental drivers of REEs in soil remain uncertain. A 3000-year soil chronosequence with uniform parent material was established in reclaimed farmland along the Yangtze River, reconstructing, for the first time, the dynamic processes of REE accumulation and fractionation over a long-time scale. Analysis of 122 soil samples showed REE concentrations ranging from 146.00 to 216.56 μg/g. Based on reclamation duration, three significant stages of REE evolution were identified: natural leaching, rapid accumulation, and stable accumulation with differentiation. Reclaimed soil after 3000 years exhibited a 14.1 % increase in REE concentrations compared to fresh sediments, attributed to anthro -pedogenic processes. Moreover, Heavy Rare Earth Elements (HREEs) accumulated faster than Light Rare Earth Elements (LREEs), particularly in deeper soils (60–100 cm), where HREE concentrations rose by 34.3 %, mainly due to acidic environments promoting HREE fixation. Additionally, the potential ecological risk posed by REEs heightened with reclamation duration, with HREEs exhibiting a sensitivity of 83 % to 94 %. Our findings stress the urgency of carefully monitoring exogenous REEs introduced through anthropogenic activities, particularly HREEs.

Origins of Low‐Oxygen Bottom Water Influenced by Tide and ENSO on the Outer‐Edge Shelf of East China Sea: Multi‐Chemical Tracer Approaches

AbstractThe East China Sea (ECS) is one of the largest marginal seas in the world with high primary productivity and a large area of low dissolved oxygen. This study observed the low‐oxygen bottom water on the outer‐edge shelf of ECS in summer seasons of 2018–2020. The contributions of various water masses to low‐oxygen waters were quantified, and the interaction between low‐oxygen water and Kuroshio water was validated by a mixing model using heavy rare earth elements (HREEs) together with potential temperature, and salinity. For further reliability verification, tracers such as δ34S and 226Ra were additionally utilized to avoid the non‐conservative processes on the shelf area. The low‐oxygen water on the shelf was clarified to be linked to the inner/middle shelf water, and dominated by Kuroshio Subsurface Water (KSSW, 81% ± 3%) and influenced by a non‐negligible extent of pore water (3.0% ± 0.5%). Our findings revealed the transport of low‐oxygen water from the outer‐shelf edge to the Kuroshio area, whose dissolved inorganic nitrogen and dissolved inorganic phosphorus contributions to Kuroshio were 34%–82% and 35%–83%, respectively. The nutrients of low‐oxygen water were regulated primarily by the origins of water and secondarily by organic matter remineralization (DIN: ∼17% and DIP: ∼24%). As control factors, the tide, especially spring tide largely enhanced the water contribution of pore water to low‐oxygen water by 67%, and the El Niño‐Southern Oscillation potentially affected the contributions of KSSW and mid‐shelf water to low‐oxygen water.

Optimization of rare earth magnet recovery processes using oxalic acid in precipitation stripping: Insights from experimental investigation and statistical analysis

Recycling the valuable metals found in spent permanent magnets (REPMs) poses a significant global challenge for the future. This study examines the efficiency of back extraction of rare earth elements (REEs) by oxalic acid solution from di-(2-ethylhexyl) phosphoric acid (D2EHPA) in recycling REPMs. To evaluate the efficiency of this process, several experiments were carried out using designed BOX-Behnken methodology to investigate the effects of various operational and chemical parameters, including stripping solution to loaded organic phase volume ratio (in the range of 1.0–2.0), oxalic acid concentration (ranging from 0.25 to 0.75 M), the stirring rate (ranged between 150 and 350 rpm), and stripping time (ranging from 15 to 45 min) on the REEs recovery and the purity of final production. Analysis of variance was applied to rigorously examine the results statistically. The results showed that more than 85 % of light and 80 % of heavy REEs can be recovered under optimal conditions. Moreover, the final product contained 43.5 % REEs and approximately 0.1 % iron. The stripping experiment using phosphoric acid as the reagent demonstrated ∼57 % light and ∼4 % heavy REEs recovery. Additionally, the recyclability of the organic phase showed its effective reuse for up to four cycles. This study underscores significant progress in the selective recovery of rare earth elements through a relatively straightforward process consuming mild reagents.

Mineralogical Characteristics of Color-Changing Garnet and the Effect of Light Path Length on Color

The color-changing garnet displays the “alexandrite effect”, changing from green in daylight to purplish-red under incandescent light. The mineralogical characteristics of color-changing garnet is analyzed using Raman spectroscopy, ultraviolet-visible (UV-Vis) spectroscopy, an electron probe, and laser ablation-inductively coupled plasma-mass spectrometry (LA-ICP-MS). The color of garnets with different thicknesses was calculated using the International Commission on Illumination (CIE 1976) L*a*b* uniform color system. The results revealed the presence of rutile inclusions in color-changing garnet. Strong absorption in both the blue-violet zone and orange-yellow zone was the main cause for the color-changing effect of garnet. The distribution pattern of rare earth elements (REE) was left-leaning, showing the enrichment of heavy rare earth elements (HREE) and depletion of light rare earth elements (LREE). As the total Cr and V concentrations increased, the area of the 574 nm absorption peak in the UV-Vis spectrum also increased, leading to a more significant variation in color ΔE*ab. The light path length of the gemstone had a significant impact on the extent of the color-changing effect. The color difference reached a maximum and the color-changing effect was most visible when the thickness of the gemstone was 5 mm.

Swelling inhibition and percolation promotion of PQ-10 on weathered crust elution-deposited rare earth ores

Weathered crust elution-deposited rare earth ores (WREOs) are rich in medium and heavy rare earth. In order to improve the in-situ leaching process, which is prone to landslides and poor permeability, cationic hydroxyethyl cellulose (PQ-10) was used as a novel green swelling inhibitor and percolation promoter and was mixed with conventional leaching agent ammonium sulfate ((NH4)2SO4) to form a composite leaching agent to study the performance and mechanism of swelling inhibition and percolation promotion. Adding PQ-10 can inhibit the hydration swelling of WREOs, promote the percolation effect of the leaching agent, improve the rare earth (RE) leaching efficiency, and reduce the impurity aluminum (Al) leaching efficiency. Compared with the conventional leaching agent 2 wt% (NH4)2SO4, the percolation time is reduced by 50% by using the composite leaching agent (0.02 wt% PQ-10+2 wt% (NH4)2SO4). PQ-10 has positively charged quaternary ammonium groups and hydrophilic group hydroxyl groups, which makes it easy to adsorb on WREOs multiple sites through electrostatic interaction and hydrogen bonding, weakening the electrostatic repulsion between mineral particles, reducing the WREOs interlayer spacing, compressing the double electric layer thickness at the solid-liquid interface, weakening the mineral hydration swelling and increasing the percolation rate. The long carbon chains of the polymer entangle and link the fine mineral particles to agglomerate them, increasing their particle size and reducing their hydration dispersion, and preventing blockage of the percolation pores caused by migration of the fine particles through the ore body with the solution. PQ-10 molecules also insert the mineral interlayer and expulsion of the internal water, further inhibiting the swelling of WREOs. Adding PQ-10 reduces the surface tension of (NH4)2SO4 solution, improving the spreading and spreading ability of the solution, reducing the adhesion work between molecules in the solid-liquid phase and the adhesion work reduction factor. It proves that PQ-10 promotes the percolation effect of the leaching process of WREOs. In addition, PQ-10 expands the leaching pore size and seepage channels, further improving the percolation rate.