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Discarded smartphones represent a valuable source of rare earths (REE), base metals and precious metals. This study focussed on the optimisation of three-stage selective leaching conditions for REE, copper and precious metals (Au and Ag), respectively, contained in printed circuit boards (PCBs) found in end-of-life smartphones. The effects of several leaching conditions, such as sulphuric acid and thiourea concentrations, were investigated using a statistical approach based on a design of experiments using Box-Behnken methodology. Optimum leaching efficiencies were achieved when PCB powder was contacted (solid concentration of 100 g/L) with (1) a 0.2 M H 2 SO 4 solution for 30 min at a temperature of 20°C for REEs; (2) a 1 M H 2 SO 4 solution with 67 g H 2 O 2 /L for 180 min at 80°C for Cu and (3) a solution of 42 g thiourea/L in 0.1 M H 2 SO 4 and 9 g Fe 2 (SO 4 ) 3 /L for 120 min at 20°C for Au and Ag. Using these optimal conditions, a complete leaching procedure included an REE solubilisation step and a base metal leaching step, both repeated twice, and a precious metal leaching step. This procedure solubilised 91% of the REE, 100% of the copper, 98% of the gold and 87% of the silver contained in the PCB powder during their respective leaching stages.

Medium-entropy alloys (MEAs) and high-entropy alloys (HEAs) are good candidates for high-temperature applications, taking advantage of their exceptional thermal stability. However, most of them contain high-priced Co elements, which limited further promotion and application. Therefore, it is imperative to elaborate HEAs/MEAs with superb oxidation resistance and relatively low cost. An economically Fe–Cr–Ni MEA, which exhibits an outstanding high-temperature oxidation resistance, was developed by Ce-adulterated. The Ce-containing Fe–Cr–Ni MEA possessed a lower oxidation rate and a higher oxidative activation energy (461.4 kJ mol−1, 14% increment compared with the reference MEA). The splendid high-temperature oxidation resistance primarily benefited from the protective oxide scales formed on the surface of MEA, which were denser, slow-growing, and well adherently. This research sheds light on exploiting low-cost MEAs with excellent resistance to oxidation for high-temperature applications.

ObjectiveTo explore the concentrations of rare earth elements (Rare earth elements, REEs) in drinking water in rare earth mining and non-mining areas in Shandong, Guangdong, and Jiangxi provinces of China.MethodsTypical rare earth mining areas and 3 non-mining areas in the 3 provinces were selected for investigation. Drinking water of people in mining areas and non-mining areas were collected for 3 consecutive days by duplicate portion method. The contents of La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu, Sc and Y in water samples were determined by inductively coupled plasma mass spectrometry (ICP-MS).ResultsThe detection rate of each REEs in drinking water of mining and non-mining area was 12.98% to 86.64% and 1.07% to 69.04%, respectively. The average content of total REEs in drinking water in the mining area was 6.974 μg/L, with the maximum of 178.290 μg/L. The main elements were Ce, La, Nd, Y, Sc and Pr (≈90.0%). The average content of total REEs in drinking water in non-mining area was 0.772 μg/L, significantly lower than that in mining area (P0.05).ConclusionThe contents of REEs in drinking water of mining area are higher than that of non-mining areas. Risk assessment of REEs exposure by drinking water should be further carried out for residents in mining areas.

To test whether praseodymium (Pr) regulates cadmium (Cd) tolerance, we explored the effects of Pr on enzymatic activities in the regeneration and biosynthetic pathways of ascorbate and glutathione in maize seedlings under Cd stress. The findings demonstrated that Cd stress increased enzymatic activities in the regeneration pathway (ascorbate peroxidase (APX), dehydroascorbate reductase (DHAR), glutathione reductase (GR), monodehydroascorbate reductase (MDHAR)) and in the biosynthetic pathway of ascorbate and glutathione (γ-ECS and GalLDH), as well as ascorbate (AsA) and glutathione (GSH) contents. However, Cd stress significantly decreased AsA/dehydroascorbic acid (DHA) ratio and GSH/oxidised glutathione (GSSG) ratio, net photosynthetic rate (Pn), chlorophylls (Chl) and carotenoids (Car) contents, maximum photochemical efficiency of PSII (Fv/Fm), photochemical quenching (qP) and quantum efficiency of PSII photochemistry (ΦPSII), as well as plant height and biomass. Application of Pr to Cd-stressed seedlings enhanced above enzymatic activities, AsA and GSH contents, AsA/DHA and GSH/GSSG ratios, Pn, Chl and Car contents, Fv/Fm, qP and ΦPSII, as well as plant height and biomass. Meanwhile, the application of Pr to Cd-stressed seedlings reduced malondialdehyde (MDA) content and electrolyte leakage. The above results indicated

The concentration of rare earth elements (REEs) in geological materials including SLRS-6 (natural water certified reference material) and JB1b, JA1, and JG2 (Standard Rock Materials of Geological Survey of Japan) can be used as a tracer to characterize various geochemical processes in earth systems. Particularly, accurate and precise determination of rare earth element concentration in natural waters is difficult due to their extremely low concentration and the interference of polyatomic oxides. In this study, we developed a method for accurate and precise determination of the REE (particularly heavy rare earth elements) concentrations in geological materials including natural waters using a multi-collector inductively coupled plasma mass spectrometer (MC-ICP-MS) and group separation by 2-hydroxyisobutyric acid (HIBA). The REEs were separated into light rare earth elements (LREEs, La–Ce–Pr–Nd), middle rare earth elements (MREEs, Sm–Eu–Gd–Tb), and heavy rare earth elements (HREEs, Dy–Ho–Er–Tm–Yb–Lu) by a cation-exchange column (AG50W-X8 200–400 mesh) using HIBA. The recovery rates of each REE in the natural water sample exceeded 98%, whereas the recovery rates of each REE in rock materials exceeded 95% except for HREEs. The method developed in this study can accurately measure the REE concentrations (particularly HREE) in geological materials without polyatomic oxide interference during the REE analysis by using the MC-ICP-MS and, thus, can correctly interpret the geochemical implications of REEs in geological systems. The determination of the Sr concentrations and Sr isotopic ratios of SLRS-6 CRM and JB1b, JA1, and JG2 SRMs is also reported, and they are shown to be in good agreement with the recommended values.

IntroductionEnvironmental pollutants, such as rare earth elements, affect human health and particularly induce reproductive system injury. Yttrium (Y), one of the most widely used heavy rare earth elements, has been reported the cytotoxicity. However, the biological effects of Y3+ in the human body are largely unknown.MethodsTo further investigate the effects of Y on the reproductive system, in vivo (rat models) and in vitro studies were performed. Histopathological and immunohistochemical examination were conducted, and western blotting assays were performed to detect the protein expression. TUNEL/DAPI staining were used to detect cell apoptosis, and the intracellular calcium concentrations were also determined.ResultsLong-term exposure to YCl3 in rats produced significant pathological changes. YCl3 treatment could induce cell apoptosis in vivo and in vitro. In addition, YCl3 enhanced the concentration of cytosolic Ca2+ and up regulated the expression of IP3R1/CaMKII axis in Leydig cells. However, inhibition of IP3R1 and CaMKII with 2-APB and KN93, respectively, could reverse these effects.ConclusionLong-term exposure to yttrium could induce testicular injury by stimulating cell apoptosis, which might be associated with activation of Ca2+/IP3R1/CaMKII axis in Leydig cells.

In recent years, there have been efforts to utilize surface water as a power source, material, and food. However, these efforts are impeded due to the vast amounts of contaminants and emerging contaminants introduced by anthropogenic activities. Herbicides such as Glyphosate and Glufosinate are commonly known to contaminate surface water through agricultural industries. In contrast, some emerging contaminants, such as rare earth elements, have started to enter the surface water from the production and waste of electronic products. Duckweeds are angiosperms from the Lemnaceae family and have been used for toxicity tests in aquatic environments, mainly those from the genus Lemna, and have been approved by OECD. In this study, we used duckweed from the genus Wolffia, which is smaller and considered a good indicator of metal pollutants in the aquatic environment. The growth rate of duckweed is the most common endpoint in observing pollutant toxicity. In order to observe and mark the fronds automatically, we used StarDist, a machine learning-based tool. StarDist is available as a plugin in ImageJ, simplifying and assisting the counting process. Python also helps arrange, manage, and calculate the inhibition percentage after duckweeds are exposed to contaminants. The toxicity test results showed Dysprosium to be the most toxic, with an IC50 value of 14.6 ppm, and Samarium as the least toxic, with an IC50 value of 279.4 ppm. In summary, we can provide a workflow for automatic frond counting using StarDist integrated with ImageJ and Python to simplify the detection, counting, data management, and calculation process.

Understanding the selectivity of metal–organic frameworks (MOFs) to complex acid gas streams will enable their use in industrial applications. Herein, ab initio molecular dynamic simulations (AIMD) were used to simulate ternary gas mixtures (H2O‐NO2‐SO2) in rare earth 2,5‐dihydroxyterephthalic acid (RE‐DOBDC) MOFs. Stronger H2O gas‐metal binding arose from thermal vibrations in the MOF sterically hindering access of SO2 and NO2 molecules to the metal sites. Gas‐gas and gas‐linker interactions within the MOF framework resulted in the formation of multiple secondary gas species including HONO, HNO2, NOSO, and HNO3−. Four gas adsorption sites were identified along with a new de‐protonation reaction mechanism not observable through experiment. This study not only provides valuable information on competitive gas binding energies in the MOF, it also provides important chemical insights into transient chemical reactions and mechanisms. [ABSTRACT FROM AUTHOR]

The rare earth elements (REEs) are crucial components of green technology and are now considered critical raw materials. One of the emerging tools in mineral exploration, laser-induced breakdown spectroscopy (LIBS), was used by several studies to determine the REE contents of different geological materials. In this study, the concentrations of selected REEs (La, Ce, Pr, Nd, Sm, Gd, Dy, and Yb) in 11 ion adsorption clays (IACs) from El Nido, Palawan, Philippines were determined using a handheld LIBS analyzer. The REE contents of the samples were also determined using inductively coupled plasma mass spectrometry (ICP-MS) to compare LIBS with the established laboratory technique. The two-sided t-test shows no significant differences for the average La, Ce, Pr, Nd, Sm, and Gd results of LIBS and ICP-MS, whereas Dy and Yb have significant differences. Based on these results, it can be concluded that LIBS can be an alternative to ICP-MS for the rapid determination of some REE in IACs. [ABSTRACT FROM AUTHOR]

For the continental rift‐related geothermal system, the hydrothermal alteration zones are rarely studied for uranium exploration. High uranium concentrations (up to 36 ppm) are shown in the altered sandstones at the Rehai geothermal field (RHGF) in Tengchong, China. To demonstrate the uranium enrichment mechanism, this study comparatively examines the trace element (uranium in particular) and rare earth element (REE + Y) concentrations of hot spring water, spring deposits (sinters and sulphates), and altered host sandstones from the RHGF of the Tengchong volcanic area. Along the central north‐south trending fault at Rehai, sinters and sulphates are precipitated from hot spring water, and the Neogene sandstones have been altered by hydrothermal fluids into zones formed of various clay minerals. The δD and δ18O values for the hot spring water indicate that the geothermal water originates from meteoric water. The spring water and hot spring deposits have identical REE distribution patterns which are featured with heavy REE (HREE) enrichment and negative Eu anomalies. Among the hot spring deposits, the yellowish earthy aggregates (tamarugite) deposited at the acidic Zhenzhu Spring have the maximum U concentration (27 ppm). The altered sandstones at Rehai, however, display the highest U concentrations (14–36 ppm). The U enrichment in the hot spring deposits and altered host rocks at the Rehai geothermal field is probably related to the multiple cycles of uranium leaching from granites, transportation upward along fault structures by geothermal water, decompression, and fixation in the hot spring deposits and/or alteration products. The results indicate that alteration zones associated with geothermal systems are also potential targets for uranium exploration. [ABSTRACT FROM AUTHOR]

Copyright of Industrial Minerals & Processing / Huagong Kuangwu yu Jiagong is the property of Industrial Minerals & Processing Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

To determine the origin of the Kohlou barite deposit, comprehensive studies on petrography, rare earth element (REE) geochemistry, oxygen and sulfur isotopes, and fluid inclusions were performed. The Kohlou deposit is located 70 km northwest of Tafresh town in Markazi Province, Iran. Barite mineralization occurs as a stratabound manto at the contact of an overlying Eocene-aged volcano-sedimentary sequence with an underlying limestone horizon. Barite is accompanied by subordinate Fe- and Mn-oxides, calcite, and quartz. Field evidence including the presence of barite veinlets cross cutting host tuffs, and the brecciated host rocks cemented by barite suggest an epigenetic origin for the mineralization. The concentration of ∑REE is very low in barites, ranging from 0.22 to 16.41 ppm. Chondrite-normalized REE patterns show LREE enrichment relative to HREE, and mostly negative La and Ce anomalies. Gadolinium (Gd) anomalies vary from negative to positive in barite samples. The Ce/La and Y/Ho ratios, as well as La and Gd anomalies confirm a terrestrial source for barite from the Kohlou deposit. The δ18O and δ34S isotopic ratios in barites fall in narrow ranges of 1.7–2.7‰ and 14.6–16.3‰, respectively, implying that sulfate originated most likely from adjacent Miocene evaporites, with minor components of magmatic sulfur and oxygen carried in mineralizing fluids. Plots of δ34S versus δ18O do not show any similarity to barites from main modern marine and pedogenic settings, while overlap with the field represented by continental barite. Salinity values in fluid inclusions range from 8.28 to 23.25 wt% NaCl + CaCl2 equivalent. Homogenization temperatures occupy the range of 139–272 °C. Fluid inclusion data indicate that basinal fluids, with minor contribution from meteoric water, were the source of mineralizing solutions. It is concluded here that faulting and brecciation of the host rocks provided the pathways needed for the upward migration of the basinal Ba-rich solutions. Barite precipitated where Ba-bearing fluids interacted evaporite deposits. [ABSTRACT FROM AUTHOR]

Copyright of Acta Geoscientica Sinica is the property of Acta Geoscientica Sinica Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

The increasing exploitation and application of rare earth elements (REEs) may induce hazardous risks to freshwater aquatic organisms. Due to the lack of water quality criteria (WQC) and sufficient reliable toxicity data, little information is available on the ecological risk of REEs in surface water. In this study, lanthanum (La) toxicity data were collected from published toxicological studies, and the data quality was assessed using a toxicological data reliability assessment tool. To obtain more toxicity data, Daphnia magna, Cyprinus carpio, and Dania rerio embryos were selected as surrogate species, and an interspecies correlation estimation (ICE) model was used to predict the toxicity of La for untested species. The species sensitivity distributions (SSDs) of La toxicity and WQC were investigated. Differences were observed in the hazardous concentrations for 5% of species (HC5), but no statistically significant differences were noted in the SSD curves between the measured acute toxicity data and the predicted data. For the SSDs constructed from the measured toxicity data, the ICE-predicted toxicity data and all acute data supplemented with the ICE-predicted data, the acute WQC values of La were 88, 1022 and 256 μg/L, respectively. According to the SSD and corresponding HC5 of chronic toxicity data, the chronic WQC was 14 μg/L. The results provide a scientific reference for establishing WQC for freshwater aquatic organisms and ecological risk assessments of REEs. [ABSTRACT FROM AUTHOR]

Rare earth elements (REEs) are strategically critical in the manufacture of advanced materials. Red mud and end-of-life NdFeB magnets can be good secondary sources for REEs, but recovery is difficult due to the high iron oxide content and small amount of REEs. Oxide mixtures whose composition of Fe, Nd, and Ga was similar to that in red mud were employed in experiments. In this study, a relatively inexpensive non-aqueous system was used to selectively dissolve Nd2O3 in a mixture with Fe2O3 and Ga2O3. The addition of ethylene glycol (EG) to HCl and H2SO4 solution depressed the dissolution of Fe2O3 and Ga2O3 from the mixtures, and thus selective dissolution of Nd2O3 was possible. The optimum conditions were as follows: (a) 1.0 M HCl in EG, 25 °C ± 1 °C, 50 g/L pulp density, 120 min, 200 rpm; and (b) 0.05 M H2SO4 in EG, 25 °C ± 1 °C, 50 g/L pulp density, 60 min, 300 rpm. Under these conditions, Nd2O3 was completely dissolved, whereas no Fe2O3 or Ga2O3 was dissolved by the H2SO4 system, and the dissolution percentage of these two oxides by the HCl system was less than 1%. Due to the selective dissolution of Nd2O3 from the oxide mixtures, it is simple to recover Nd. An efficient process can be developed for the recovery of REEs from red mud and end-of-life NdFeB magnets by applying our results. [ABSTRACT FROM AUTHOR]

BACKGROUND: Phytoremediation by hyperaccumulators (such as Dicranopteris dichotoma) is widely used for the remediation of rare earth tailings in China. Accordingly, a large amount of rare earth‐rich plant residues is produced. Anaerobic digestion could convert biomass into energy. In this study, the anaerobic digestion performance of D. dichotoma, which is rich in rare earth elements (REEs), was investigated. Cellulose, xylan, and glucose served as the model substrates to explore the effects of La(III) on hydrolysis and methane production using batch anaerobic digestion. RESULTS: The results indicated that the La(III) concentration of 500 mg/L inhibited methane production from cellulose with the reduciton of 20%. Inversely, no significant difference was found in the cumulative methane yield from glucose with different La(III) concentrations. The microbial community results showed that the lack of cellulose hydrolyzing bacteria, such as Clostridium III and Clostridium XlVa, may be the main reason for the inhibition of methane production. Furthermore, the methane yield of REE‐rich D. dichotoma was 181.5 ± 14.6 mL/g VS and the La(III) concentration of luquid digestate was only 2.20 mg/L. CONCLUSION: The inhibition of La(III) on anaerobic digestion of lignocellulose was mainly in the hydrolysis process of cellulose, while the inhibition of xylan hydrolysis was relatively weak, and it had no significant effect on methanogenesis process of glucose. La(III) showed a small effect on the methane production of REE‐rich D. dichotoma due to a small amount of release into the liquid digestate. Anaerobic digestion may be a feasible way for treating lignocellulose plants contaminated with rare‐earth minerals. © 2022 Society of Chemical Industry (SCI). [ABSTRACT FROM AUTHOR]

The reaction mechanism at the interface between CaO-Y 2 O 3 composite oxide refractories and superalloy melt during vacuum induction melting of Ni-based superalloys was investigated. Once the reaction occurred, the interfacial layer consisted of exterior CaS layer and interior CaYAlO 4 layer. CaS was formed by the desulfurization reaction of CaO and S from alloy melt. While the CaYAlO 4 was formed by the reaction of 12CaO·7Al 2 O 3 or Al 2 O 3 (CaO and Y 2 O 3 were replaced by Al), CaO and Y 2 O 3. The whole interfacial reaction was: CaO(s)+[S] Ni (l)+[Al] Ni (l)+Y 2 O 3 (s)=CaYAlO 4 (s)+ CaS(s)+[Y] Ni (l). [ABSTRACT FROM AUTHOR]

[Display omitted] • An electroactive REE-biochar composite was prepared. • Role of REE-biochar on methanogenesis was affected by its pyrolysis temperature. • B800 significantly enhanced electron transfer efficiency and methanogenesis. • The B800 group obtained the highest Rm, which was 94% higher than in control. High solid anaerobic digestion (HSAD) is a promising technology to manage Dicranopteris pedata biomass (DPB) that generated from the phytoremediation process of rare earth tailings area. Rare earth element (REE)-rich DPB can be converted to biochar via a direct pyrolysis approach, yet the efficacy of REE-biochar in the HSAD process remains unclear. Here, three types of REE-biochars (B300, B500 and B800) were produced at 300, 500 and 800 °C. The results showed that elevating pyrolysis temperature improved the REE-biochar properties such as specific surface area (SSA), electrical conductivity (EC), REE content, and graphitization degree, but reduced its electron exchange capacity (EEC). Compared to B300 and B500, the B800 addition clearly boosted methane yield (up to 60% and 29%) and maximum methane production rate (up to 21% and 15%). Microbial analysis showed that B800 not only enriched the acidogenic bacteria (e.g., Ruminofilibacter) and electroactive microbes (e.g., DMER64 and Syntrophus) but also enhanced microbial metabolisms and electron transfer ability. Further analysis showed that B800 facilitated methanogenesis probably by coordinating the interaction of key genera through quorum sensing system and modulating electron transfer through its intrinsic graphitic matrices and REE oxides. This study offered a new approach to recycling REE-rich biomass and a guidance to design functional biochar material for improving the HSAD performance. [ABSTRACT FROM AUTHOR]

• Carboxylated mesoporous carbon was synthesized from soft-templated mesoporous carbons (CMC) • 16 REEs and 20 non-REEs were obtained in Coal Fly Ash (CFA) leachate. • 80–90% REEs were extracted & 20–100% REEs were recovered in multiple cycles. • Distribution Coefficient denoted that CMC has higher affinity for REE extraction. • Ratio of extracted & recovered REEs over non-REEs confirm the selectivity of CMC. The separation of Rare Earth Elements (REEs) from non-conventional sources is very critical to maintain the supply-chain balance of REEs in the Western world. Despite Coal Fly Ash (CFA) being designated as a prominent non-conventional source of REEs and several studies have reported on the extraction of REEs from CFA, the selectivity of REEs with respect to non-REEs in the CFA has never been reported. In this work, for the time, we have reported the selectivity of REEs over non-REEs using carboxylated mesoporous carbon (CMC) as the sorbent. The CMC was produced by carboxylating the soft-templated mesoporous carbon and then it was characterized successfully for porosity, FTIR, and SEM-EDX. The leachate produced from REEs contains 16 REEs and 20 non-REEs from groups 1 through 3 and 6 through 15 of the modern periodic table. The REEs were extracted within 80–90% in the 3 cycles along with the elements from groups of 1,3, 5, 8, and 11. Although a few other elements were also extracted, the values of the distribution coefficient confirmed that the CMC has a much higher affinity towards REEs except the non-REEs from groups 1 and 3. In the recovery mode, the REEs were recovered in the range of 20–100%, and heavier REEs demonstrated a better recovery. The recovery percent of non-REEs was also much lower compared to that of REEs, except for the elements from groups 3, 8, and 11. The non-REEs from group 3 demonstrated the highest competition, which can be attributed to the fact the REEs also belong to the same group of the periodic table. The ratio of extracted and recovered REEs over non-REEs was always greater than unity, suggesting that the CMC was selective towards REEs over non-REEs in extraction and recovery. The overall results suggest that CMC can potentially be used for selective extraction and recovery of REEs from coal fly ash. [ABSTRACT FROM AUTHOR]

[Display omitted] • Pr and Cu regulate the electron redistribution of Co 2 P. • Electrodeposition method to solve the problem of poor stability. • Excellent HER performance at high current density. • Catalytic mechanism involving electron redistribution, energy bands and crystalline/amorphous interfaces. • A strategy for rare earths to regulate electron redistribution together with Cu. In this work, rare earth element Pr and transition metal Cu were anchored on the surface of Co 2 P nanowire arrays (PrCu@Co 2 P) by constant-current electrodeposition to redistribute the electrons of catalysts, which enhanced the electrocatalytic activity. Hydrogen evolution reaction (HER) in alkaline solution, the catalyst achieves current densities of −10 (ƞ 10) and −700 mA cm−2 with overpotentials of 65 and 280 mV, respectively. As well, outstanding long-term cycling stability was demonstrated with almost insignificant degradation of catalytic performance over 48 h. The exceptional electrocatalytic performance of PrCu@Co 2 P is primarily due to the electron redistribution effect caused by Pr and Cu, which restructures the energy bands and optimizes the d-band center of the catalysts. This adjustment brings the Gibbs free energy of adsorbed hydrogen (ΔGH*) of the catalysts close to zero, thereby enhancing their inherent activity for the hydrogen evolution reaction. Interestingly, a similar trend was observed when the strategy for redistributing surface electrons was used other rare earths, which provides a new idea for co-doping transition metal phosphides (TMPs) with rare earth and transition metal elements. [ABSTRACT FROM AUTHOR]

Neodymium-iron-boron (NdFeB) has become the most prominent permanent magnet alloy, with a wide variety of applications and an ever-increasing demand. Their recycling is important for securing the supply of critical raw materials used in their manufacturing. The use of organic acids such as acetic acid has been of recent interest for the recycling of waste NdFeB magnets. Despite achieving good leaching efficiencies, the published literature has not properly investigated the effects of key factors influencing the acetic acid leaching process and their respective interactions, which has led to conflicting findings as to what conditions are optimal. The present work goes to show that no such optimum exists by taking a look at the major factors (concentration, solid-to-liquid ratio, time, and temperature) and their interactions. The results show that leaching efficiencies >95% and even up to 100% can be achieved using a variety of different conditions showing that the leaching reaction is quite flexible, which is helpful for a potential upscaling of the process. The separation of the leached elements presents another problem in NdFeB magnet processing. As a novel application, this work investigated iron separation from the acetic acid leachate by the means of simple and inexpensive aeration. It was found that up to 99% of iron could be precipitated as FeO(OH) (goethite) within 2 h at pH 5 and 80 °C, while only minor neodymium co-precipitation was observed (5%). Separation of iron from the leachate can help obtain purer REE products in further processing.

Rare earth elements (REEs) have been widely applied as fertilizers in farmland of China for decades to improve the yield and quality of crops. Unfortunately, adverse effects on plants have been observed due to overdosing with REEs. Until now, the toxicology of REEs was mainly evaluated based on phenotypic responses, but knowledge gaps still exist concerning their metabolic effects. Here, the physiological responses and nontargeted metabolomics studies were combined to systematically explore the potential effects of La and Ce on a crop plant, wheat Triticum aestivum. It was observed that REEs accumulated in the shoots of wheat, with significant reduction of the shoot biomass at higher exposure doses. The disturbance of photosynthesis and induced oxidative stress were identified by analyzing indicators of the photosynthetic (chlorophyll a/b, carotenoid and rubisco) and antioxidant systems (POD, CAT, SOD, GSH and MDA). Furthermore, the global metabolic profiles of REEs treatment groups and the non-exposed control group were screened and compared, and the metabolomic disturbance of REEs was dose-dependent. A high overlap of significantly changed metabolites and matched disturbed biological pathways was found between La and Ce treatments, indicating similarity of their toxicity mechanism in wheat shoots. Generally, the perturbed metabolomic pathways were mainly related to carbohydrate, amino acid and nucleotide/side metabolism, suggesting a disturbance of carbon and nitrogen metabolism, which finally affected the growth of wheat. We thus proved the potential adverse effect of inappropriate application of REEs in crop plants and postulated metabolomics as a feasible tool to identify the underlying toxicological mechanisms.

The influences of Ce, Sm and Yb on cavitation erosion of NAB alloy in 3.5% NaCl solution are evaluated using mass loss, SEM, 3D morphology and Tafel plot, respectively. The results show that the addition of Ce or Sm or Yb enhances the mechanical property of NAB alloy, and the sizes of κⅠ and κⅡ phases within NAB alloy decrease with adding Ce or Sm or Yb, resulting in the prevention of the propagation of the cracks caused by cavitation erosion initially originated at the phase boundaries between α and κ phases, and finally the cavitation erosion damage significantly decreases with adding Ce or Sm or Yb. The corrosion of NAB alloy in 3.5% NaCl solution can promote the cavitation erosion of NAB alloy, while the corrosion resistance of NAB alloy increases with the addition of Ce or Sm or Yb, and then the cavitation erosion resistance is accordingly improved with the addition of rare earth element.

Abstract Cerium has been used as an implanted alloy additive for many years for it can enhance the mechanical properties of the alloy and restrain the corrosion of the implant. Moreover, cerium oxide nanoparticles are often used as an antibacterial material. However, there were few researches focusing on the antibacterial properties of Ce3+ and Ce4+ ions, instead of their corresponding oxide, as potential antibacterial coatings. Thus in this work, we loaded Ce ions into the porous structure of the ZIF‐8 nanoparticles and co‐deposited them with hydroxyapatite as a composite coating onto anodized titanium dioxide nanotubes array in order to test whether it can improve the anti‐corrosion and antibacterial properties of the materials without affecting the biocompatibility.

Background. Rare earth element (REE) composition of atmospheric dust has recently been used to trace potential sources of dust pollution. Objective. The present study aimed to determine the sources of atmospheric pollution in the study area using REE patterns and determine their level of pollution. Methods. Twenty-five (25) atmospheric dust samples were collected in the study area, with five samples each from an industrial area, traffic area, dumpsite area, residential area and remote area in Ibadan, southwestern Nigeria. In addition, five (5) topsoil and two (2) rock samples (granite gneiss) were collected for comparison. Concentrations of REE were determined by inductively coupled plasma mass spectrometry (ICP-MS). Results. The ratio of lanthanum/cerium (La/Ce), especially in some locations in industrial area (1.5), traffic area (1.5) and to some extent dumpsite area (1.1) was higher than in soil (0.2), upper continental crust (0.5) and the minimum value of fluid catalytic crackers (1.0). Generally, the respective average values of the ratios of La/praseodymium (Pr), La/neodymium (Nd) and La/samarium (Sm) in industrial area (32.1, 7.8 and 52.6) and traffic area (14.9, 4.4 and 26.8) were higher than their respective averages in soil (4.4, 1.1 and 6.2), rock (5.7, 1.9 and 14.1), upper continental crust (4.4, 1.1 and 6.6) and the minimum value in fluid catalytic crackers (5.8, 3.7 and 37.0). Meanwhile, their corresponding value in the dumpsite area, residential area and remote area were lower or similar to the geological background levels. Discussion. The contamination factors of REEs in the atmospheric dust of the industrial area and traffic area were classified as heavily contaminated, especially with light lanthanoid elements in REE. The degree of contamination of REEs in the atmospheric dust of industrial area (30.9) and traffic area (18.8) fell within the considerable contamination category. The high values of the light lanthanoid ratio and the contamination indices were attributed to their emission from the fired-power plant and vehicular exhaust. Conclusions. Most of the composition of the atmospheric dust was sourced from the local geology of the study area as observed in the residential area and remote area, while the contamination in the industrial area and traffic area was attributed to human activities. Competing Interests. The authors declare no competing financial interests.

Alloying of Mg with rare-earth (RE) elements proved to be beneficial for their in-vitro and in-vivo performance. In this work, a novel WN43 (Mg-4 wt%Y-3 wt%Nd) alloy with a well-defined composition was prepared, where, unlike in the commercial WE43 alloy, the possibly harmful RE mischmetal was substituted by less toxic Nd. A modern spark plasma sintering (SPS) technique was used to effectively produce WN43 samples from atomized powders. Sintering temperatures of 400 °C – 550 °C and holding times of 3 or 10 min were used and well-compacted final materials were successfully prepared. It was shown that a superior combination of corrosion and mechanical properties was attained in the samples sintered at 500 °C and 550 °C, while the effect of sintering time was rather negligible. The performance of this material was exceptional within the group of Mg alloys prepared by powder metallurgy and comparable with conventionally prepared alloys. Moreover, it was shown that a great variety of mechanical and corrosion characteristics can be obtained by altering the SPS parameters so as to fulfill case-specific requirements typical of biomedical materials. Consequently, the novel WN43 alloy prepared by SPS seems to be a particularly suitable material for biomedical use.

An Al-Zn-Mg-Cu alloy has high specific strength, good corrosion resistance, fracture toughness and fatigue resistance. It is one of the most important structural materials in the fields of aviation, aerospace, weapons and transportation; in particular, it plays a huge role in the field of aerospace. In order to optimize the strength, toughness and corrosion properties of an Al-Zn-Mg-Cu alloy, the focus of research on this alloy has always been on the alloying process. The effects of the main alloying elements, trace alloying elements and rare earth elements on the microstructure and properties of Al-Zn-Mg-Cu alloys are briefly introduced in this paper, and future research directions are proposed.

[Display omitted] • Phosphorylated porous phenolic resins (PO-PPRs) were prepared with POCl 3 post-modification. • PO-PPRs with hierarchical pore structures demonstrated a broad pH working range (3.0–7.0). • PO-PPRs exhibited excellent adsorption capacities of light and heavy REEs (63.9–118 mg/g). • The Nd3+/Al3+ separation factor of PO-PPR-1 reached 24. • PO-PPRs can efficiently extract and recycle low-concentration REEs from tailing wastewater. Efficient extraction and recycling of rare earth elements (REEs) from low-concentration complex tailing wastewater is critical to meeting the growing industrial demands and optimizing resource utilization. In this work, three phosphorylated porous phenolic resins (PO-PPRs) were prepared via the phosphorylation of phenolic hydroxyl groups with POCl 3 , and employed to extract REE3+ from both simulated and practical low-concentration REE3+-containing aqueous solution. The PO-PPRs, characterized by hierarchical pore structures, exhibit high adsorption capacities for both light and heavy REE3+ ions over a broad pH working range from 3.0 to 7.0, along with fast adsorption kinetics (<30 min). And the maximum adsorption capacities of PO-PPRs for Nd3+, Dy3+ and Y3+ were found to be 104.1, 118.0 and 63.9 mg/g, respectively. Furthermore, the introduction of phosphonic groups significantly improves the REE3+ adsorption selectivity against various interfering metal ions such as Na+, K+, Ca2+, Mg2+, and Al3+. For instance, the Nd3+/Al3+ separation factor (S.F.) of 24 exceeded that of most commercial resins and reported materials. In a simulated mixed multi-element aqueous solution system containing Nd3+, Dy3+, Y3+, Al3+, Ca2+, Mg2+, Mn2+, K+ and Na+, PO-PPR-1 extracted 82.5% of total REE3+ while maintaining Al3+ adsorption efficiency of less than 13%. Moreover, the extraction efficiency of total REE3+ for PO-PPR-1 in pretreated practical wastewater from ion-adsorbed ores tailing reached 99.6%. Additionally, PO-PPRs demonstrated easy regeneration and excellent recycling performance after 5 consecutive adsorption–desorption cycles, confirming their promising application potential in low-concentration REEs extraction. [ABSTRACT FROM AUTHOR]

Zircon-melt partitioning of Ce is sensitive to the redox conditions of magmas as zircon crystallizes, because Ce4+ is far more compatible than Ce3+ in zircon. This makes Ce in zircon an effective tool to constrain magma oxygen fugacity (f O 2). However, trivalent light rare earth element (LREE) concentrations in zircon analyses are easily inflated by inclusions and alteration, which makes estimation of the concentration of Ce3+ within the zircon structure very difficult. We propose new treatments of measured Ce concentrations in zircon and of zircon/melt Ce partitioning to improve estimates of Ce4+ and Ce3+ in zircon and the melt from which it grew. To minimize the LREE contamination effect that plagues zircon analysis, we propose a revised method to quantify Ce3+ and Ce4+ in zircon that extrapolates using a logarithmic function of ionic radius of the middle to heavy rare earth elements. We then present improved Ti-dependent zircon/melt partition coefficients for both Ce3+ and Ce4+ based on the lattice strain model to estimate Ce3+ and Ce4+ in the coexisting melt. Derived estimates of Ce4+ in both zircon and melt are robust; estimates of Ce3+ are less so. We then calculate Ce4+/Ce3+ of the melt using both Ce3+ melt obtained from our new partition coefficients and typical Ce total concentrations in melts based on the relatively narrow global measured range. The f O 2 values calculated using these estimated Ce4+/Ce3+ ratios and the model of Smythe and Brenan (2016) for analyzed zircons from a range of tectonic settings fall within plausible ranges. We suggest that our new approaches, particularly with respect to estimating Ce4+ concentrations, may be broadly useful for constraining magma oxidation state, especially for studies of detrital zircon whose provenance is unknown. • An alternative method of determining Ce3+ and Ce4+ in zircon and melt. • Improved zircon/melt partition coefficients for Ce3+ and Ce4+. • Contaminated zircon analyses can be screened out by La concentrations. • Modeled melt Ce4+/Ce3+ is capable of constraining magma oxidation states. [ABSTRACT FROM AUTHOR]

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. • Indigenous microorganisms from regolith-hosted REE deposits exhibit high adsorption efficiencies for REEs. • Taxonomic classification of microorganisms significantly influences REE adsorption selectivity • Distinct functional groups on the microbial surface correspond to the adsorption preference towards REEs. [ABSTRACT FROM AUTHOR]

Bauxite deposits are an important source of Al and also host a variety of critical metals, including rare earth elements (REEs). However, the parent rocks of bauxite deposits generally have low REE contents, leading to uncertainty over the REE sources and enrichment mechanisms. In this study, we report high REE (2095 ppm; Ce = 1340 ppm) contents in the Lijiatian bauxite deposit in Luxi County, western Hunan Province, South China. The Lijiatian bauxite deposit is the largest deposit in Hunan Province, with a total Al resources exceeding 7 × 106 tons. The ore-bearing strata in the lower Permian Liangshan Formation (ca. 275 Ma) are comprised a 3–5-m-thick bauxite layer (bauxite ore/clay) and an underlying 4–8-m-thick Fe layer (Fe ore/Fe-rich clay). The high REE contents in the bauxites can be attributed to the widespread presence of bastnäsite. The bastnäsite commonly coexists with authigenic chlorite, which formed at temperatures of 221–285 °C, indicative of a hydrothermal origin. Uranium–Pb dating of the bastnäsite yielded an age of 141.4 ± 7.0 Ma, indicating a hydrothermal overprint occurred during the Early Cretaceous, which resulted in the enrichment of REEs in the bauxites. The high contents of REEs, Ba, and P in the Cambrian Niutitang Formation black shales indicate it was a potential source of these elements for bastnäsite and coexisting barite and apatite. The deep-seated hydrothermal fluids (enriched in HF, CO 2 , and H 2 S) associated with the late Yanshanian extensional tectonic event in South China (155–123 Ma) ascended along fractures. The ascending fluids interacted with the black shales, extracting REEs, Ba, and P. When the fluids reached a certain depth, they mixed with the infiltrating basinal waters to form a mineralising fluid. The fluid then migrated towards the bauxite layers, underwent cooling and depressurisation, and precipitated bastnäsite, barite, apatite, and chlorite. We propose that a hydrothermal event led to the enrichment of REEs in the bauxites in Hunan Province. Considering the scarcity of REEs in the parent rocks of bauxites worldwide, hydrothermal activity likely has a key role in REE enrichment in bauxites. [Display omitted] • The main mineral hosting REE (Ce) in Permian bauxite from southern China is Bastnäsite. • The bastnäsite formed during the Cretaceous period due to hydrothermal fluid activity. • The REEs are source from the basement black shale. [ABSTRACT FROM AUTHOR]

A novel electrode material of Ni–Co bimetallic hydroxide composite multi-wall carbon nanotubes (La–NiCo LDH/MWCNTs/NF) doped with rare earth elements was prepared on nickel foam (NF) by a one-step hydrothermal method and doped with different concentrations of La3+ ions. The introduction of La3+ ions can increase the layer spacing of LDH materials. The acidification of MWCNTs on the surface of NF can also enhance the collection effect of NF. The synergistic effect of MWCNTs and La3+ ions further improves the specific capacitance of the material. At the current density of 1 A g−1, the maximum specific capacitance of the sample with 5 % La3+ ion concentration reaches 4396.0 F g−1, and the capacitance retention is 70.31 % after 3000 cycles of a single electrode. When assembled into a device, the device obtains a high energy density of 77.86 Wh kg−1 at a power density of 800.0 W kg−1. After assembling into an asymmetric supercapacitor, it has undergone 8000 cycles of performance testing, and the capacitance ratio is only reduced by 4.9 %. It shows good electrochemical cycle performance. This work provides a new way to study the doping of rare earth elements for supercapacitor materials. • La–NiCo LDH/MWCNTs/NF electrode achieves a high specific capacity of 4396 F g−1 at a current of 1 A g−1. • The ASC device presents a remarkable energy density of 77.86 Wh∙kg −1. • After 8000 cycles, the ASC device reduced the specific capacitance by only 4.9 %. [ABSTRACT FROM AUTHOR]

• Coal ash from multiple sources was compared for extractability of REEs. • Optimization of suitable pre-treatment to enhance extractability was performed. • Morphological differences between coal ash samples were established. • A holistic flow sheet was developed for enhanced rare earth elements extraction. The conditions under which coal ash is formed largely dictates the association of valuables within its matrix. An optimum utilization of coal waste in commercial level is only feasible upon performing an in-depth comparative study of fly ash (FA), bottom ash (BA) and laboratory ash (LA). In the present study, two coal ash samples were acquired from a power plant in India (1200–1300 °C), whereas the one under laboratory conditions was prepared at 815 °C. The total concentrations of rare earth elements (hereafter abbreviated as REEs) were- LA (873 ppm), FA (509 ppm) and BA (373 ppm) and their respective outlook coefficients were-LA (0.78), FA (0.87) and BA (0.88). Sequential extraction revealed that the chosen LA possessed 40 % of the total REE in extractable form, whereas both FA and BA possessed only 10 % of the total REE in extractable form. Magnetically isolated Fe-containing matrix with 50 % Fe 2 O 3 was observed in case of FA. Alkaline pre-treatment to enhance the extractability of REEs was performed using both NaOH and Na 2 CO 3 , under varying temperature from 400–850 °C. The optimum condition was deduced to be using NaOH at 400 °C. Sodium silicate was eliminated during water leaching, from which Si was precipitated at neutral pH. The leaching parameters were optimized on these alkali roasted coal ash samples, and 0.5 M tartaric acid at 90 °C stirred for 60 min demonstrated 75–80 % increase in leaching of REEs as compared to baseline leaching of 27 % (LA), 5 % (FA), 12 % (BA). Significant morphological change was observed post alkaline pre-treatment and acid leaching. NaOH roasting resulted in cracks and fractures on the surface of spherical BA and FA samples followed by development of pores during the leaching process. Solvent extraction was performed with 10 % (v/v) D2EHPA (di-(2-ethylhexyl) phosphoric acid) in kerosene with an additional scrubbing stage (5 % oxalic acid solution) to enhance the purity of REE extraction. [ABSTRACT FROM AUTHOR]

Air humidity is a major factor that degrades the performance and long-term stability of metal-oxide-semiconductor (MOS) based gas sensors. In this work, we propose an encapsulation strategy by coating a mesoporous silica molecular sieve (SBA-15) on rare earth doped tin oxide (RE-SnO 2) nanofibers for humidity-resistant hydrogen detection. In this design, the hydrophobic SBA-15 sieve layer effectively blocks the water molecules without affecting hydrogen diffusion, while the RE dopant greatly improves the responsivity and lowers down the operating temperature of the sensors, As a result, the Er-SnO 2 /SBA-15 and Tb-SnO 2 /SBA-15 sensors respectively show the maximum response values of 27.71 and 33.68 (to 10 ppm hydrogen at 280 °C, 4.67 and 5.67 times that of the bare SnO 2 ones, respectively), short response/recovery time (< 1.0 s / < 1.0 s), as well as a low limit of detection for hydrogen (200 ppb) and a good gas selectivity. Under the protection of the SBA-15 sieve layer, the response retention of the sensors is significantly improved when the humidity increases from 25% to 85% RH (Er-doping, from 38.8% to 60.0%; Tb-doping, form 25.6–57.8%). Besides, further analysis on enhancement mechanism of response indicates that the SBA-15 coating contribute about 1/3 of the response enhancements via its own hydrogen physical adsorption capacity and the induced oxygen vacancies during the calcination processes. [Display omitted] • Humidity-resistant hydrogen sensor was designed using the electrospun RE-SnO 2 nanofibers and the mesoporous silica coating. • Both RE doping and SBA-15 coating benefit the sensing response of SnO 2 -based sensor towards hydrogen. • The increased response of the SBA-15 encapsulated sensors was due to the decreased R g. • The SBA-15 coating also increases the response value via increasing the O V s and the hydrogen adsorbed on its surface. [ABSTRACT FROM AUTHOR]

In this study, pure nickel oxide (NiO) and Europium (Eu) doped NiO nanoparticles were synthesized using the solgel method. Nickel (II) acetate tetrahydrate was used as the Ni source and Europium chloride was used as the Eu source. The synthesis process was carried out at 80 °C for 3 hours. The synthesized nanoparticles were annealed at 450 °C for 1 hour. The compounds forming the nanoparticles were analyzed by X-ray diffraction (XRD). The morphologies of nanoparticles were investigated by field emission scanning electron microscopy (FE-SEM). The elements that make up the nanoparticles were determined by energy dispersive X-ray spectroscopy (EDX). It was observed that the synthesized particles were in nano size and the morphologies changed with the doping of Eu. It was determined that as the Eu contribution increased, the lattice parameters and unit cell volumes increased. As the Eu contribution increased, the crystallite size decreased. As a result of the structural and morphological characterizations, it was observed that the Eu contribution was successfully realized. It was concluded that the produced pure and Eu doped NiO nanoparticles could find use as nanomaterials in the semiconductor industry. [ABSTRACT FROM AUTHOR]

The difficulties associated with dyeing alginate fibers by conventional dyeing processes have been a major limitation hindering the large-scale application of alginate fibers in the textile industry. The main aim of this study is to use plasma equipment for free radical graft polymerization of methacryloyloxyethyl trimethylammonium chloride (DMC) to achieve a better dyeing effect on cationically modified alginate fibers by direct dyeing using a saltless dyeing process. The treated alginate fibers were dyed by direct dyes and characterized by SEM, FTIR-ATR, XPS, K/S value determination and single-fiber breaking strength analysis. The results show that the DMC was successfully grafted onto the alginate fibers, the modified alginate fibers had good dyeing ability with high K/S values; and the alginate fibers maintained their breaking strength of 2.33 cN/dtex after dyeing, corresponding to a decrease of only 15.5 % (red), 1.3 % (yellow), and 4.8 % (blue) compared to that of the original fiber. The dyed alginate fibers also showed good washing fastness, which was better than grade 4. All the results indicate that upon subjection to atmospheric plasma, DMC was efficiently embedded into the alginate fibers, making the fiber cationic and effectively overcoming the charge repulsion between the fiber and the dye under salt-free conditions. This study may provide a valuable method for the alginate fiber dyeing industry. [ABSTRACT FROM AUTHOR]

The wide usage of neodymium (Nd) in industry, agriculture, and medicine has made it become an emerging pollutant in the environment. Increasing Nd pollution has potential hazards to plants, animals, and microorganisms. Thus, it is necessary to study the toxicity of Nd and the mechanism of Nd transportation and detoxification in microorganisms. Through genome-scale screening, we identified 70 yeast monogene deletion mutations sensitive to Nd ions. These genes are mainly involved in metabolism, transcription, protein synthesis, cell cycle, DNA processing, protein folding, modification, and cell transport processes. Furthermore, the regulatory networks of Nd toxicity were identified by using the protein interaction group analysis. These networks are associated with various signal pathways, including calcium ion transport, phosphate pathways, vesicular transport, and cell autophagy. In addition, the content of Nd ions in yeast was detected by an inductively coupled plasma mass spectrometry, and most of these Nd-sensitive mutants showed an increased intracellular Nd content. In all, our results provide the basis for understanding the molecular mechanisms of detoxifying Nd ions in yeast cells, which will be useful for future studies on Nd-related issues in the environment, agriculture, and human health. [ABSTRACT FROM AUTHOR]

This study was carried out to evaluate the extent of carbonate crash in some Niger Delta oil wells and the levels of heavy metals (HMs) and rare earth elements (REEs) as useful fingerprinting tools in the characterization of the oil wells. Thirty-nine (39) rock samples were collected from three (3) oil wells in the Niger Delta, Nigeria. The carbonate contents were determined using Chittick apparatus while the elemental concentrations were determined using Atomic Absorption Spectrophotometry. Results of the study indicated that the carbonate contents of the rock samples decreased with increasing depth, due to a possible higher-than-average dissolution of CaCO3 and/or excess bio-SiO2 production. Among the investigated HMs, manganese had the highest mean concentration while nickel had the lowest mean concentration. Cerium had the highest mean concentration while lanthanum had the lowest mean concentration among the REEs. Mean V/Ni ratios of Oil Well 1 (3.21) indicated marine organic matter input while Oil Well 2 (2.47), and Oil Well 3 (2.16) indicated organic matter input of both marine and terrestrial sources. V/(V + Ni) ratios (>0.5) of the oil wells indicated that the organic matter was deposited under anoxic conditions. Variations in the distribution patterns of HMs, REEs, and carbonate content of the rock samples of Niger Delta oil wells indicated that the organic matter source and depositional environment were quite similar. [ABSTRACT FROM AUTHOR]

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Changsha kilns were exported to more than 20 countries and regions and were an essential part of the culture in the central Yangtze River during the late Holocene. Reconstructing the hydrological landform and sedimentary history of its surrounding areas (Shizhu) is significant for further constraining any links between regional paleoenvironmental change and the human−land relationship in the lager river valley. To examine paleo−hydrological and provenance evolution, the rare earth element (REE) and trace element ratio from the Shizhuping (SZP) section were analyzed. The SZP section records the paleo−hydrological evolution over 1300 years: river network cutting plain landscape—Shizhu Lake—river floodplain—Shizhu Lake reformation—Shizhu flat. This section was labeled as stages IV to I, respectively. The deposition of stages IV was wind and dust accumulation during the Last Glacial. The provenance of stages III (1288–1094 a.BP) was wasted from the ceramic production process. The layer of stage II (1094–380 a.BP) was in two parts. In stage II−2 (1094–890 a.BP), provenance was dominated by granite. Sedimentary rocks became the source of stage II−1 (890–380 a.BP). In stages I (380 a.BP–), the primary material sources were anthropogenic bedding and weathering erosion deposits around the slope. During the Medieval Warm Period, the climate was warm and humid, and the rising water level of the Xiangjiang River led to the emergence of lakes in the Shizhu area. The migration of northern China into Changsha kiln brought new technology and labor. In the late Five Dynasties, the climate turned dry, and the falling water level of the Xiangjiang River caused Changsha kiln to lose its commercial wharf. [ABSTRACT FROM AUTHOR]

Rare earth elements (REEs) are critical metallic materials with a broad application in industry and biomedicine. The exponential increase in REEs utilization might elevate the toxicity to aquatic animals if they are released into the water due to uncareful handling. The specific objective of our study is to explore comprehensively the critical factor of a model Lanthanide complex electronic structures for the acute toxicity of REEs based on utilizing zebrafish as a model animal. Based on the 96 h LC50 test, we found that the majority of light REEs display lower LC50 values (4.19–25.17 ppm) than heavy REEs (10.30–41.83 ppm); indicating that they are atomic number dependent. Later, linear regression analyses further show that the average carbon charge on the aromatic ring (aromatic Cavg charge) can be the most significant electronic structural factor responsible for the Lanthanides' toxicity in zebrafish embryos. Our results confirm a very strong correlation of LC50 to Lanthanide's atomic numbers (r = 0.72), Milliken charge (r = 0.70), and aromatic Cavg charge (r = −0.85). This most significant correlation suggests a possible toxicity mechanism that the Lanthanide cation's capability to stably bind to the aromatic ring on the residue of targeted proteins via a covalent chelating bond. Instead, the increasing ionic bond character can reduce REEs' toxicity. In addition, Lanthanide toxicity was also evaluated by observing the disruption of photo motor response (PMR) activity in zebrafish embryos. Our study provides the first in vivo evidence to demonstrate the correlation between an atomic number of Lanthanide ions and the Lanthanide toxicity to zebrafish embryos. [ABSTRACT FROM AUTHOR]

Copyright of Hydrometallurgy of China is the property of Hydrometallurgy of China Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Coal deposits can provide novel stratigraphic markers for reconstructing the evolution history of a sedimentary basin and correlating sedimentary successions. Age dating was conducted on zircons harvested from the No. 6 coal seam within the Heidaigou Mine, Inner Mongolia. Two-kilogram samples were taken, and the recovered zircons were analyzed for U–Pb isotopic and rare earth elements (REE). The REE results of the zircon grains showed that all the zircon grains were enriched in heavy rare earth elements (HREE) but depleted in light rare earth elements (LREE). In addition, zircons from the No. 6 coal seam had strongly positive Ce (Ce/Ce* = 2.4–224.6) and strongly negative Eu anomalies (Eu/Eu* = 0.1–0.6). Combined with the clear oscillatory zones in the cathodoluminescence images, all the zircon grains of the No. 6 coal were characteristic of zircons with magmatic origins. The 206Pb/238U ages of 34 zircon grains produced a narrow age population of 303–286 Ma, with a weighted average age of 293.0 ± 1.5 Ma (mean-squared weighted deviation = 1.5). Therefore, we infer that the No. 6 coal in the Heidaigou Mine was deposited during the Early Permian, and the Carboniferous–Permian boundary should be located stratigraphically lower than the No. 6 coal. The zircon U–Pb geochronology is a useful tool to determine the depositional ages of non-marine-influenced coal. [ABSTRACT FROM AUTHOR]

This work investigates the microstructure and inclusions of a compacted graphite iron (CGI) alloyed by Ce and La rare earth (RE) elements. In our study, alloying elemental distribution and solute segregation were characterized by methods of secondary ion mass spectrometry (SIMS) and a three-dimensional atom probe (3DAP) with high sensitivity and spatial resolution. RE sulfide, MgS, carbide, and composite inclusions formed during solidification and provided heterogeneous nucleation cores for the nucleation of the graphite. Significant solute clustering in the matrix, coupled with the segregation of solute to grain boundaries, was observed. C, Mn, Cr, and V were soluted in cementite and promoted the precipitation of cementite, while Si was found to be soluted in ferrite. Cu is usually distributed uniformly in ferrite, but some Cu-rich atom clusters were observed to segregate towards the interface between the ferrite and cementite, stabilizing the pearlite. In addition, P, as a segregation element, was enriched along the boundaries continuously. The RE elements participated in the formation of inclusions, consuming harmful elements such as As and P, and also promoted the heterogeneous nucleation of the graphite and segregated, in the form of solute atoms, at its interfaces. [ABSTRACT FROM AUTHOR]

The corrosion behaviour of as-cast binary Mg–0.3Ce, Mg–1.44Nd, Mg–0.63Gd and Mg–0.41Dy (wt%) alloys was investigated in DMEM+10% FBS solution using electrochemical and weight loss tests. The results revealed that the alloys with heavy RE elements (Gd and Dy) exhibited the lowest corrosion rate compared to the alloys with light RE elements (Ce and Nd). The cytocompatibility of the Mg–RE alloys was assessed via live/dead straining after 3 and 7 days. The results show that Mg–0.63Gd alloy is a suitable candidate for biomedical applications.