Rare Earth Element Concentrations Research Articles

Advancing towards technology readiness: Continuous-flow electrosorption for thorium separation from rare earth processing by-products

This study focuses on the development of a curated separation system aimed at separating thorium ions as part of a recovery plan for managing the thorium radionuclide in the rare earth element (REE) processing industry. As a step towards advancing technology readiness, the separation system employs the electrosorption technique, which involves the migration and storage of thorium ions in the electrical double layers on the porous surface of a carbon-based electrode. Using a prototype electrosorption cell operated at an applied voltage of 1.0 V, the system successfully achieved a thorium ion recovery rate of 84.5 ± 0.29 %, with an impressive electrosorption capacity of 105.26 mg-Th/1 g-carbon. Notably, despite the presence of higher concentrations of REE as competing ions, greater selectivity towards thorium was observed which likely attributable to its larger ionic radius, higher electron affinity, and greater distribution coefficient. These findings highlight the efficacy of the curated separation system and its potential to balance between REE economic significance as well as a protection to the environment.

The sequential migration of rare earth elements (REE) in WE43 magnesium alloy during anodic oxidation treatment

Rare earth elements (REE) like Y, Gd and Nd could migrate and enrich on WE43 magnesium alloy (WE43) surface during anodic oxidation. However, the specific mechanism is still unclear. In this study, WE43 alloy was modified by anodizing for 10 min, 30 min, 1 h and 2 h in KOH solution, respectively, followed by heating treatment for 2 h at 500℃. The obtained materials were named as AO-10, AO-30, AO-1 h and AO-2 h in turn. The surface morphology, phase compositions, surface potentials, REE contents of these materials were studied. In addition, the contents of REE in materials and KOH solution were investigated before and after electrolysis. The results found that surface morphology, phase composition were different with different electrolytic time. The phase compositions changed from Gd2O3 and Nd2O3 on AO-10 surface to Y2O3 and Gd2O3 on AO-2 h surface. Moreover, The contents of REE on material surfaces would first increase and then decrease with over time. Surface potentials confirmed that the regions rich in REE had lower potentials than Mg substrate. The contents of REE in materials and KOH solution further revealed that Nd ion was the first to ionize into the solution, followed by Gd, finally by Y. The migration rates of REE were different, which depends on their electric potentials. The migration rate of Nd was the fastest in all elements. It would preferentially migrate to material surface and entered into electrolyte solution in the oxidation process. Hence, the migration of REE from the inside to the surface of WE43 metal is sequential during anodic oxidation.

Quantitative evaluation of anthropogenic sources and health risks of rare earth elements in airborne particulate matter

Rare earth elements (REEs) have emerged as contaminants in airborne particulate matter (PM); however, their anthropogenic sources remain poorly quantified, and associated health risks are unknown. This study investigates the REE distribution across eight sizes of airborne PM during July and December in Qingdao, a major Chinese port city. Our results reveal a single coarse-mode distribution with REE concentrations. In contrast, fine PM (size: 0.43–2.1 μm) exhibits notable enrichment of La and Ce compared to Al and other REEs. This study traces La and Ce enrichment to fluid catalytic cracking catalysts (FCCC)-related sources, including refinery and ship emissions, by comparing the REE fractionation in samples with potential sources. We quantify the contributions from FCCC-related sources to La (July: 33.6 % ± 3.2 %, Dec.: 46.4 % ± 5.2 %) and Ce (July: 16.5 % ± 14.3 %, Dec.: 30.3 % ± 12.2 %) by comparing measured concentrations with predictions derived from neighboring REEs, a method previously used exclusively in aquatic systems. For the first time, supply ratios of refinery and ship to FCCC-related La are calculated using a two-component mixing model based on the [La]FCCC/[V]anth, revealing the dominance of refinery emissions (July: 97.3 % ± 0.6 %, Dec.: 99.6 % ± 0.1 %). Furthermore, a global review of La and Ce anomalies that integrates published REE data with our findings reveals a widespread distribution of positive anomalies. The significantly positive correlation between La and Ce anomalies underscores FCCC-related emissions as a global source in fine PM, contributing 0–92 % (mean: 35 % ± 33 %) for La and 0–72 % (mean: 21 % ± 24 %) for Ce. Although the non-carcinogenic health risks of Ce are generally low globally, concerns should be raised in areas near source emissions, where Ce health risks sharply increased along with its concentrations. There is urgently need to establish a threshold value for La, owing to its global enrichment. This study provides novel insights into the sources and health implications of REEs in airborne PM.

Study of mineralogy and distribution of rare earth elements in coal block of Eastern Coalfield, India

ABSTRACT Coal by-products are continuing to be explored as secondary resources for extraction of rare earth elements (REEs). Nevertheless, the knowledge of their geological abundance is still scarce compared to the high global demand. The present investigation aims to study the distribution of REEs in coal samples acquired from Eastern coalfield, India. A total of 27 samples collected from two boreholes (RGCF-1and RGCF-2) were thoroughly analyzed. The average REE concentration in RGCF-1 was 724 ppm, while for RGCF-2, it was 658 ppm with a distribution pattern of Ce>La>Nd>Y>Pr>Sc>Sm>Gd>Dy>Yb>Er>Eu>Ho>Tb>Tm>Lu. Quartz, feldspar, sanidine, magnetite, hematite, anatase/titanate and illite were deduced to be the major mineral phases in these coal ash samples prepared at 815°C. In RGCF-1, REEs were associated with magnetite, whereas in RGCF-2, they were primarily with aluminosilicate and titanate minerals. The overall concentration of critical REEs varied from 122.5 to 387.8 ppm with an outlook co-efficient (C outl) of 0.58–1.26, indicative of the suitability of the chosen coal block for future exploration. Such an exploration-based investigation on abundance of REEs in the Indian subcontinent coupled with the knowledge of their mineralogical association is beneficial in not only understanding their enrichment but also coining a suitable extraction strategy for these valuables.

Improvements in recovery of rare earth elements (REEs) from coal via fluidized-bed combustion: Thermal alteration of REE mineralogy and its impact on element extractability

The extraction of rare earth elements (REE) from coal ash has attracted significant attention, but satisfactory solutions have not yet been achieved. Indeed, the REE extractability is largely determined by the transformation behavior of REE during coal combustion. This study found that the controlled combustion conditions of circulated fluidized-bed boiler (CFB) can both utilize the heating value and enhance the recovery of REE from coal. Tests were conducted using a bituminous coal with REE concentration of approximately 149 ppm in an industrial 35 t/h CFB boiler with controlled boiler loads and coal sources. Advanced automated image analysis by scanning electron microscopy (AIA-SEM) and sequential leaching procedure were employed to clarify the speciation transformation behavior of REE in boilers and investigate the effects of these transformations on the leachability of REE. Approximately 75 % of REE partitioned into fly ash and enriched in particles < 45 μm (∼710 ppm) after combustion. Acid leaching tests under mild conditions (1 M HCl at 60 ℃ and S/L = 1:25) performed on coal, bulk ashes, and sieved ashes revealed an improvement in REE leaching ratio from coal (21.34 %) to fly ash (71.07 %). Particle size played a crucial role in acid extractability, particularly for middle and heavy REE in cyclone ash but had no influence on those in fly ash. The dominant forms of REE in coal including Ca-REE fluorocarbonates (36.7 %), aluminophosphates (12.0 %), and organic-bound REE (approximately 20 %) significantly decreased, contributing to the formation of leachable rare earth oxides (∼65 %) in ash. Furthermore, the small size of REE mineral grains in coal (over 50 % below 5 μm) and extensive mineral fragmentation occurring in boiler resulted in the enrichment and enhanced REY leachability in fine ash.

Improving the reliability of using rare earth elements as soil erosion tracers

Rare earth elements (REEs) have been successfully used as tracers in field-scale erosion experiments to provide spatially distributed erosion data for process-based soil erosion models. This study aimed to demonstrate how differences in the erodibility of individual REEs naturally present in the soil affect the evaluation of data from such experiments.A four-year field experiment was carried out at an experimental site used for arable farming to investigate soil erosion. The concentrations of tracer REEs (Pr, Sm, Gd, Ho, Er, and Yb) and reference REEs (all other REEs) were evaluated and compared both in the soil and eroded sediment.The tracer REE concentrations in the eroded sediments were consistently significantly higher than the average background soil concentrations. Even when compared with the maximum values of background soil concentrations, enrichment of Er, Sm, and Ho in the sediment was still evident. However, in some cases, the reference REE concentrations in the sediment were often higher than the maximum soil background concentrations by more than 10%. These enrichment differences indicate the varying erodibility of individual REEs during erosion. The elements chosen as tracers could also be enriched in the sediment from their natural background sources, thus influencing the measured concentration values in the sediment after tagging.This study demonstrated that different REEs naturally present in soil exhibit varying degrees of erodibility, which affects data evaluation in soil erosion tracing experiments using REE oxides as tracers. Therefore, the reliable application of the REE tracer method can only be suggested under certain requirements defined in this study.

The Rare Earth Element Distribution in Marine Carbonates as a Potential Proxy for Seawater pH on Early Earth

Understanding the marine environment of early Earth is crucial for understanding the evolution of climate and early life. However, the master variable of Archean and Proterozoic seawater, the pH, is poorly constrained, and published ideas about the pH range encompass ~7 pH units from mildly acidic to hyperalkaline. To better infer ancient seawater pH, we examine the possibility of a seawater pH proxy using rare earth elements (REEs) in marine carbonates. The principle is based on increasing concentrations of heavy rare earth elements in solution relative to the light REEs with decreasing pH due to REE complexation and scavenging. We calibrated such an REE pH proxy using pH variability in modern seawater and tested the proxy with ~100 REE measurements from 13 separate carbonate formations. We compared our pH estimates derived from the REE proxy to published pH estimates of Cenozoic and Neoproterozoic seawater that use the established pH proxy of boron isotopes (δ11B). REE-pH estimates agree with the Cenozoic and the Ediacaran δ11B-pH proxy based on the type of carbonate and boron isotopic composition at corresponding times. The uncertainty in our REE-pH proxy can probably be explained by model assumptions, noise from freshwater influence, siliciclastic input, and diagenesis. This proof-of-concept study demonstrates that the REE-pH method provides pH estimates comparable to boron isotope pH estimates within uncertainties, which potentially could constrain changes in Precambrian seawater pH to better understand the coevolution of life and early Earth’s environment.

Rare earth elements (REEs) in soils and plants of Bangka Island (Indonesia) focussing on (hyper)accumulation

Abstract Background and Aims Indonesia is one of the most biodiverse regions in the world, but only a few metal hyperaccumulator plants have been reported from this vast country. This study aimed to discover rare earth element (REE) hyperaccumulator plants on Bangka Island, an area known to have REE enriched soils associated with tin placer deposits. Methods Prior to this study, herbarium specimens at the Universitas Bangka Belitung Herbarium were screened using non-destructive X-ray Fluorescence (XRF) scanning to detect specimens with anomalous REE concentrations. Fieldwork was subsequently conducted to collect samples from plant species suspected to be (hyper)accumulators based on the earlier XRF survey. Scanning electron microscopy and micro-XRF were used to verify the possibility of surface contamination by soil particles in plant specimens, and inductively coupled plasma atomic emission spectroscopy (ICP-AES) was used to determine total elemental concentrations in the plant material. Results Blechnopsis orientalis was found to hyperaccumulate REEs up to 3000 µg g−1 as well as arsenic up to 2100 µg g−1. The non-destructive analysis found no dust or soil contamination on B. orientalis specimens, confirming it as a genuine REE and arsenic hyperaccumulator. Additionally, the known REE hyperaccumulator Dicranopteris linearis was confirmed to be a REE hyperaccumulator on Bangka Island. Conclusion Blechnopsis orientalis is a REE hyperaccumulator with high potential for phytoextraction as it is a faster growing and larger species than D. linearis. As B. orientalis and D. linearis are native to Bangka Island, both should be studied further for their application in rehabilitating and extracting REEs from the (abandoned) tin mine areas.

Evaluation of coal mine drainage and associated precipitates for radium and rare earth element concentrations

Coal mine drainage (CMD) and associated metal-rich precipitates have recently been proposed as unconventional sources of rare earth elements (REEs). However, the potential occurrence of radium (Ra), a known carcinogen, with the REE-bearing phases has not been investigated. We hypothesized that Ra may occur in solids that are precipitated from CMD as a “radiobarite” solid solution ((Ba,Sr,Ra)SO4) and/or adsorbed with hydrous metal oxides. REEs have been documented to sorb or co-precipitate with iron (Fe), manganese (Mn), and aluminum (Al) oxyhydroxide in CMD solids. Likewise, Ra has been documented to sorb to hydrous Fe and Mn oxides especially where sulfate (SO4) and/or barium (Ba) concentrations are insufficient to precipitate radiobarite. Thus, we conducted the first-ever survey of Ra concentrations in corresponding CMD water and solid samples in the United States. Samples were analyzed from 4 untreated and 9 treated CMD sites in both the bituminous and anthracite coal regions of Pennsylvania across a range of pH and SO4 concentrations. The dissolved Ra in CMD was relatively low (<0.5 Bq/L), consistent with radiobarite solubility; however, CMD solids were largely composed of amorphous Fe, Al, and Mn oxyhydroxide and silicate minerals. Ra was associated with Mn-enriched CMD solids, upwards of 875 Bq/kg. Total REE + yttrium (Y) content in the CMD solids was enriched upwards of 3600 mg/kg and was significantly correlated with Al content. These preliminary results suggest that REE extraction may target Al-rich solids to avoid Ra in Mn-rich solids.

Analysis and Prediction of the Leaching Process of Ionic Rare Earth: A Data Mining Study with Scarce Data

To unveil the impact of each condition variable on the leaching efficiency index during the heap leaching process of rare earth ore and establish a prediction model for leaching conditions and efficiency, common parameters in the heap leaching process of rare earth ore were selected. In addition, the pilot-scale test data were collected over 50 days. Based on the collected data, the Ordinary Least Squares (OLS) linear regression method was used for fitting analysis to determine each variable’s influence on the change in leaching efficiency. The results indicated a linear relationship between the flow rate of the leaching solution and leaching efficiency. In contrast, no obvious linear relationship was observed between other condition variables and leaching efficiency. Spearman’s rank correlation coefficient was calculated to analyze the nonlinear correlation between the abovementioned variables and the leaching efficiency index. The correlation coefficients were found to be −0.78, 0.88, −0.93, −0.53, 0.71, and −0.93 for ammonium content in the leaching agent, pH of the leaching agent, rare earth content, ammonium content in the leaching solution, pH of the leaching solution, and the flow rate of the leaching solution, respectively. This suggests that the flow rate of the leaching solution, rare earth content, and pH of the leaching agent significantly influence leaching efficiency, thus affecting the rare earth leaching efficiency index. Based on the correlation analysis results of leaching conditions and efficiency, a dataset with limited data trained by the common Ordinary Least Squares model, linear regression model, random forest model, and support vector machine regression model was selected to develop a prediction model for the leaching process data. The results indicated that the random forest model had the lowest mean square error of 7.47 among the four models and the coefficient of determination closest to 1 (0.99). This model can effectively analyze and predict condition variables’ data and leaching efficiency index in the heap leaching process of rare earth ore, with a prediction accuracy exceeding 90%, thus providing intelligent guidance for the heap leaching process of rare earth ores.

Geochemical characteristics of Neoproterozoic metavolcanic rocks of Ariab Auriferous Volcanogenic Massive Sulfide deposit, Red Sea hills, North-East Sudan

The Ariab volcanogenic massive sulfide (VMS, ∼118.3 Mt with >2 Moz Au recovered) district is part of the Ariab-Arbaat belt located in the Haya terrane, Red Sea Hills, Northeast Sudan. The gold-bearing gossan and VMS deposits are mainly hosted by Neoproterozoic bimodal volcanic succession. The petrogenesis, age dating, metallogenic evolution, and tectonic environment as well as the relationship between the metals occurrences and hosting materials remain poorly constrained and controversial. The study aims to investigate the geochemical characteristics of metavolcanic rocks of Ariab Auriferous Volcanogenic Massive Sulfide. XRF and ICP-MS techniques were employed to analyze major, trace, and rare earth elements content. The metavolcanics composition of Ariab VMS hosting rocks ranging from basalt to rhyolitic lava with variable pyroclastics. The chemical affinity varies from sub-alkaline tholeiitic to calc-alkaline nature, raising an argument against the possibility of fractional crystallization. The Ariab VMS metavolcanics were likely formed in the intra-oceanic arc tectonic environment. Ariab mafic lava is characterized notably by high Cr and Ni concentrations. The negative and positive anomalies in trace element profiles are typically ocean island basalt patterns, implying minimal crustal contamination. The geochemical results of dacitic and rhyolitic rocks reveal an assimilation-fractional-crystallization process, including the possibility that plagioclase-rich restite was formed in the parent magma source with a significant contribution from the old crust. The mobility of elements such as Zn, Cu, Pb, Ag, Au, As, and Co complicates the determination of their primary abundances. The partitioning behavior of REEs, the geochemical signatures of chalcophile elements, and their associations with VMS deposits, underscores the complex interaction between igneous processes and subsequent hydrothermal alteration.

Geochemical Characteristics of Soil Rare Earth Elements within Spontaneous Combustion Coalfields of Rujigou Coal Mine

(1) Background: The spontaneous combustion of coal (SCC) not only consumes huge amounts of coal resources but also causes environmental degradation. Rare earth elements (REE) can be taken as an effective indicator to evaluate the environmental effects of SCC. Coal in the Rujigou Mine has been spontaneously combusting for hundreds of years. (2) Methods: The geochemical properties of REE and major elements in the soil of the Rujigou coal mine are methodically examined to reveal the environmental effects of SCC. (3) Results: Soil REE concentration in the Rujigou mine is 216.09 mg/kg, and there is an enrichment of light rare earth elements (LREE) and a depletion of heavy rare earth elements (HREE), LREE/HREE in Rujigou mine was 5.52. The spontaneous combustion of coal could change the vertical distribution of REE, which is conducive to the enrichment of LREE. According to the Eu anomaly and δCe/δEu, the source of material in this mine may be derived from the terrigenous clastic rock controlled by weak reduction. Aluminum and titanium have similar geochemical behavior to REE, especially LREE. The concentration of sulfur is negatively correlated with REE, especially HREE. Calcium, sodium, and magnesium all had a negative correlation with LREE. (4) Conclusions: The spontaneous combustion of coal can lead to the fractionation of light and heavy rare earth elements, resulting in the enrichment of LREE and depletion of HREE.

Rapid quantitative analysis of multiple rare earth elements in NdFeB alloys based on laser-induced breakdown spectroscopy (LIBS) and random forest (RF)

NdFeB material has excellent comprehensive magnetic properties, which plays a crucial role in the field of rare earth magnetic materials, and is one of the important basic materials to support modern high-tech industries. In the production of NdFeB alloys, the control of rare earth elements (REEs) is directly related to the quality and resource utilization efficiency of NdFeB materials. Therefore, the prediction of REEs content in NdFeB alloys is of great research significance and application value for the quality control of products, the enhancement of production efficiency and reduction of energy consumption by the rare earth material industry. In this study, a combination of laser-induced breakdown spectroscopy (LIBS) and random forest (RF) was used to investigate the quantitative analysis of four REEs (Nd, Pr, Tb and Dy) in NdFeB alloys. Firstly, the original LIBS spectra were screened by principal component analysis-mahalanobis distance (PCA-MD). Then, the effects of different data processing methods on the screened LIBS spectra were explored, and next, the feature variables were extracted from the preprocessed spectral data by the variable importance measurement (VIM). In order to further verify the prediction performance of the model, the prediction results of the RF models based on the different methods were compared. Finally, a PCA-VIM-RF calibration model was established on the basis of the optimized spectra, selected feature variables and parameters. Leave-one-out cross validation (LOOCV) was used to optimize the parameters of PCA-MD method, spectral preprocessing method and variable importance thresholds during the construction of the calibration model. The results show that the PCA-VIM-RF model has better prediction performance than the RF calibration model based on the raw spectra. For the PCA-VIM-RF calibration method of Nd, Pr, Tb and Dy elements, the values of R2CV are 0.9991, 0.9998, 0.9986, and 0.9984, respectively, the values of RMSECV are 0.06296%, 0.02788%, 0.04647% and 0.05252%, respectively. The values of R2P are 0.9508, 0.9975, 0.9691 and 0.9457, respectively, and the values of RMSEP are 0.6082%, 0.09205%, 0.5776% and 0.2631%, respectively.The above results indicate that LIBS combined with PCA-VIM-RF algorithm is a promising method for rapid quantitative analysis of REEs in NdFeB alloys without complicated sample preparation, which can provide some new ideas or strategies for the future research, development and quality control of rare earth materials.

Critical differences between typical arc magmas and giant porphyry Cu ± Au systems: Implications for exploration

Abstract Porphyry Cu, and porphyry Cu-Au deposits, are associated with arc magmatism and their ore-forming systems generally follow the magmatic evolution of typical arcs. However, most arc magmas are barren and giant economic porphyry Cu ± Au deposits are rare. In this study, we model variations in rare earth element concentrations in the evolving arc magmas and giant porphyry Cu ± Au systems to quantify the percentage of the fractionating minerals required to produce the observed changes. We find that, during the andesitic stage of fractionation, ore-forming systems in thick crusts fractionate ~35% more amphibole than an average of thick arc magma systems (the thick-crust reference suite) and that ore-forming systems in thin crusts fractionate twice as much amphibole as their equivalent thin-arc magma reference suite. Thick-crust ore-forming suites also fractionate ~50% less plagioclase, and thin-crust ore systems ~40% less plagioclase, than their associated reference suites during the same andesitic stage of fractionation. Taken together, these observations imply that ore-producing magmas are appreciably wetter than their associated barren reference suites. Our modelling also shows that 80% more amphibole is required to reproduce the andesite stage of fractionation in the thick-crust reference suite than in its thin-crust equivalent, suggesting that magmas produced under thick crusts are wetter than those produced under thin crusts. On the other hand, the chalcophile element contents of the thick- and thin-crust ore-forming systems are similar to and higher than those of the thick- and thin-crust reference suites, respectively. Therefore, we suggest that the high water content plays a critical role in the formation of giant porphyry Cu ore in thick crusts, whereas both high chalcophile contents and high water contents are required to form giant porphyry Cu-Au deposits in thin crusts. The high fraction of amphibole fractionation in giant economic porphyry suites, compared with their relevant reference suites, results in lower Y in the ore-associated suites and this difference increases with fractionation. As a consequence, plots of Y against MgO can be used to identify porphyries that have economic potential and are preferred to Sr/Y plots because they are less affected by the intense alteration associated with giant porphyry Cu ± Au deposits.

Distribution, provenance, contamination, and probabilistic ecological risk of rare earth elements in surface sediments of Jiulong River estuary and adjacent watershed

Rare earth elements (REE) are increasingly recognized as emerging micropollutants in the environment, and concerns surrounding their presence are steadily growing. However, the understanding of possible pollution and ecological risks of REE in river sediments is relatively scarce. To address this, an investigation into the distribution, origins, pollution levels, and potential ecological risks of REE in sediments along the Jiulong River Estuary and adjacent watersheds was conducted. The results revealed that ΣREE in sediments ranged from 54.98 to 156.05 mg/kg along the Jiulong River and its estuary. The REE concentrations generally decreased from the Jiulong River to the estuary. Cluster analysis and geochemical parameter ratios suggested the high REE concentrations in Jiulong River may be derived from fertilizer and coal combustion. The sediments REE was normalized using the chondrites and exhibited apparent fractionation between LREE and HREE. Additionally, the REE in sediments was characterized by LREE enrichment and negative Ce and Eu anomalies. The evaluation of geo-accumulation and enrichment factors indicated that Gd, Yb, Lu, Tb and Dy were the elements most highly enriched in the sediments. Sites labeled S1–S3 and S5 were classified as moderately polluted, with Lu posing a moderate potential ecological risk, while other elements presented only mild ecological risks. Our findings suggest that anthropogenic activities significantly influence the pollution and potential ecological risks of REE in river sediments. Therefore, attention should be paid to the management of emerging contaminants in rivers and estuaries to protect ecosystems and local populations from potential risks associated with the accumulation of REE in sediments.

Petrogenesis of K-rich and high-mg adakitic rocks in the North Dabie terrane, China: products of early cretaceous orogenic collapse

ABSTRACT Understanding orogenic collapse is key to comprehending the evolution of continental collision orogens. The Dabie orogen is a collapsed continental collision orogen that provides an ideal window for revealing orogenic collapse. Here, we conduct fieldwork, whole-rock geochemistry, and zircon U-Pb dating of the Daoshichong pluton in the North Dabie terrane to elucidate the collapse mechanism of the Dabie orogen. The Daoshichong pluton is composed of quartz monzodiorite and mafic microgranular enclaves (MMEs) with an Early Cretaceous (~130 Ma) crystallization age. The Daoshichong pluton is strongly deformed and ductile, displaying a gneissic structure. The quartz monzodiorites are K-rich and high-Mg adakitic rocks. They contain 60.2–63.3 wt.% SiO2 and have high K2O (2.88–3.42 wt.%) and MgO (2.08–3.04 wt.%) contents with relatively high Mg# values (44.4–49.3). They exhibit high Sr (673–819 ppm) and low Y (11.4–20.9 ppm) and heavy rare earth elements (e.g. Yb: 0.94–1.87 ppm) contents, resulting in high Sr/Y (35.1–72.0) and (La/Yb)N (15.7–36.1) ratios. The MMEs exhibit geochemical characteristics similar to those of the Early Cretaceous mafic – ultramafic rocks of the Dabie orogen. They have low SiO2 contents (48.1–51.9 wt.%) and high MgO contents (3.27–5.62 wt.%) with high Mg# values (47.3–51.2). They also exhibit relatively high Ni (16.6–63.6 ppm), Cr (30.5–164.6 ppm), Y (18.2–25.8 ppm) and Yb (1.50–1.94 ppm) contents and high Sr/Y ratios (53.7–109.5). Evidence from fieldwork and geochemistry distinctly indicates magma mixing during magma evolution between the MMEs and the quartz monzodioritic host. Thus, the Daoshichong quartz monzodioritic host and the MMEs can be interpreted as a mixture of mantle-derived magma and over-thickened lower continental crust-derived adakitic melt. Previous studies suggest that the Early Cretaceous (~130 Ma) high-Mg adakite-like rocks are distributed only along the eastern margin of the Dabie orogen (i.e. along the Tan – Lu Fault). This study is the first to report a homochronous (~130 Ma) K-rich and high-Mg adakite-like pluton in the core of the Dabie orogen. Our results suggest that a whole delamination of the over-thickened orogenic root caused the orogenic collapse, subsequently triggering crust – mantle interactions, dome structure, and magmatism in the Dabie orogen.

Rare earth elements in biology: From biochemical curiosity to solutions for extractive industries.

Rare earth elements (REEs) are critical for our modern lifestyles and the transition to a low-carbon economy. Recent advances in our understanding of the role of REEs in biology, particularly methylotrophy, have provided opportunities to explore biotechnological innovations to improve REE mining and recycling. In addition to bacterial accumulation and concentration of REEs, biological REE binders, including proteins (lanmodulin, lanpepsy) and small molecules (metallophores and cofactors) have been identified that enable REE concentration and separation. REE-binding proteins have also been used in several mechanistically distinct REE biosensors, which have potential application in mining and medicine. Notably, the role of REEs in biology has only been known for a decade, suggesting their considerable scope for developing new understanding and novel applications.

Recovery and concentration of Eu(III) from phosphogypsum leachate using ouricuri endocarp

Ouricuri endocarp was utilized as a biosorbent for the recovery of europium (Eu(III)) from aqueous solutions and rare earth elements (REEs) from authentic leachate derived from phosphogypsum, which encompasses various REEs. Various characterization techniques were applied to analyze the physicochemical and adsorptive properties of the biosorbent. The results indicate that the adsorption kinetic data conform well to the pseudo-first-order model, while the Liu model describes the equilibrium data well. Ouricuri endocarp and Eu interactions are favorable and spontaneous. The maximum adsorption capacity for Eu(III) is determined to be 22.9 mg/g according to the Liu model. Based on experimental results and adsorbent characteristics, the proposed adsorption mechanisms between ouricuri endocarp and Eu include ion exchange and electrostatic interactions as the primary mechanisms. The Eu(III) recovery is also feasible as a continuous flow process demonstrating inclined breakthrough curves and lower values of the length of the mass transfer zone. Ouricuri endocarp demonstrates its selectivity for recovering various REEs from authentic phosphogypsum leachate. It achieves a 98% recovery rate for Eu and approximately 60% for Ce, La, and Nd, affirming its efficacy under real-world conditions. Finally, concentration of REE was done by ashing loaded ouricuri endocarp, and a solid with around 34% (in weight) of REE is obtained.

Mössbauer study of iron oxide nanoparticles

AbstractMagnetic nanoparticles have recently attracted attention for biochemical and medical applications like drug delivery and hyperthermia for a variety of reasons with most important being their stability, chemical compatibility, and suitable magnetic properties like moderate specific mass magnetization. Cobalt ferrites are a well‐studied family of materials and the partial substitution of Fe3+ cations by rare earth (RE) ones may be used to tune the magnetic properties. In the present work pure and substituted Co ferrite nanoparticles with nominal stoichiometry CoFe2−xRxO4 (R = Yb, Gd; x = 0.05, 0.1, 0.3) synthesized by the co‐precipitation method are studied with 57Fe Mössbauer spectroscopy to determine the incorporation of RE ions in the spinel lattice. The fitting procedure was based on the standard spinel model using two sextets for the octahedral and the tetrahedral coordinated positions of Fe atoms. All isomer shift values were found within the typical range of high spin ferric ions while quadrupole splitting values strongly suggest that there is a substitution preference; RE ions replace iron ones in octahedral sites. The inversion parameter was found to decrease with RE content (lowest value about 0.534 for CoFe1.90Yb0.10O4) and thermal treatment always results in changing the material toward normal spinel, while pure CoFe2O4 was inverse. Thermal treatment of substituted materials in ambient air at temperature range 1500–1700 K for 12 h increase crystallite size and changes the degree of inversion.

Re-evaluating the origins of sands in the Gurbantunggut Desert and its role as an aeolian dust contributor

We analyzed the trace and rare earth element contents of the desert sands and loess deposits in the Junggar Basin. Combined with previously published data, and using principal component analysis, our results provide insights into the sand provenances of the Gurbantunggut Desert in eastern Central Asia (CA); the genetic links between deserts and loess deposits in CA; and the specific sources in CA for the aeolian dust in North Pacific Ocean sediments. The results demonstrate the spatial heterogeneity of the geochemistry of sand across the Gurbantunggut Desert. The desert sands in the northern and western parts of this desert are mainly derived from the Altai and Junggar mountains, respectively, as supported by the directions of sand fluxes. However, Beitashan Mountain makes a negligible contribution due to the lack of fluvial transport and westward sand fluxes. However, more sediment samples need to be collected to confirm the contribution of Tianshan Mountains. Our findings also indicate that the Gurbantunggut Desert did not contribute significantly to loess accumulation on the northern slopes of the Tianshan Mountains, in accordance with the weak genetic relationships between loess deposits and deserts in western CA. We attribute this to the limited ability of the CA deserts to produce and supply dust-sized particles. Additionally, using the Metropolis-Hastings sampling approach, we find that the Gurbantunggut Desert is not the source region in CA for the fine dust particles in North Pacific Ocean sediments. Overall, our results contribute to a deeper understanding of the aeolian systems in CA and their impacts on the dust cycle at a hemispheric scale.