Effects Of Rare Earth Elements Research Articles

Selection of optimal models for predicting growth stress in Artemisia desertorum by comparison of linear regression and multiple neural networks: Take the construction of a green mine in the Bayan Obo mine as an example

In recent years, more and more countries are focusing on the control of mining sites and the surrounding ecological environment, and the new environmental concept of green mines has been proposed. By investigating the ecological background of a mine site, pollution and ecological imbalances in the mine can be predicted, managed or transformed. This study investigated the effects of rare earth elements on plant growth in the Baotou Bayan Obo Rare Earth Mine and evaluated soil contamination and subsequent remediation through the measured plant height. Using linear regression, BP(Back Propagation) neural networks, GA-BP(Genetic Algorithm- Back Propagation) neural networks, ELM(Extreme Learning Machine) and GA-ELM(Genetic Algorithm- Extreme Learning Machine) model prediction instruments, the different rare earth solution concentrations were set as input values and the heights of Artemisia desertorum, which as the model plant, were set as output values in the prediction. The results showed that the linear regression predicted the standard error of single La(III), Ce(III) solution and compound La(III) + Ce(III) solution for Artemisia desertorum growth stress was on the high side, 7.02%− 8.92%; the efficiency range of each group of models under BP neural network, GA-BP neural network and ELM neural network were 1.15%− 2.53%, 0.85%− 1.28%, 1.76%− 3.53%; while the efficiency range under GA-ELM neural network was 0.59%− 0.68%, with average error values and predicted values close to the true values. Among them, the MAPE of GA-ELM neural network are significantly lower than other models, and the error decreases with increasing concentration of the compound solution. So GA-ELM neural network can be used as an efficient, fast and reasonable optimal model for predicting the growth stress of Artemisia desertorum in Bayan Obo mining area. The experimental results can provide a theoretical basis for assessing the risk of soil rare earth contamination in the area, evaluating the expectation of later remediation, and provide a degree of new ideas for the construction of green mines.

Effect of rare earth element Y(III) on short‐term denitrification performance of anaerobic ammonia oxidized granular sludge

AbstractBACKGROUNDThe ammonia‐nitrogen wastewater generated during rare‐earth mining poses a serious hazard to the environment around the mine. This type of wastewater is difficult to treat using conventional biological methods due to its low carbon‐to‐nitrogen ratio. Anaerobic ammonia oxidation (anammox) has become the first choice for treating rare earth mine wastewater. However, the effect of rare earth elements (REEs) in wastewater on anammox bacteria has been insufficiently studied, and this limits the application of this process. Yttrium is a rare earth element present in wastewater, and the study of its effect on anammox can help in the application of this process in rare earth mine wastewater.RESULTSThe effect of Y(III) on anammox granular sludge was studied using batch experiments. Anammox activity decreased with increasing Y(III) concentration, from 64.78 ± 0.28 to 17.15 ± 2.70 mg g−1 VSS day−1. The semi‐inhibitory concentration (IC50) of Y(III) for anammox activity was 30.36 mg L−1. Y (III) exhibited low promotion and high inhibition of anammox bacterial extracellular polymer secretion (EPS). Comparing the kinetic models, the Loung model is better suited for describing the kinetic equation of substrate concentration on anammox.CONCLUSIONThe acute toxicity of Y(III) to anaerobic sludge is influenced by the substrate and Y (III) concentrations. EPS‐based defence strategies play an important role in counteracting the toxicity of Y(III). The Edwards model fits the experimental data well and is suitable for predicting the inhibition of anammox activity by the substrate concentration. © 2022 Society of Chemical Industry (SCI).

Correction to Effects of Rare Earth Elements’ Physicochemical Properties on Their Stabilization during the Fe(II)aq-induced Phase Transformation of Ferrihydrite

Correction to Effects of Rare Earth Elements’ Physicochemical Properties on Their Stabilization during the Fe(II)_<i>aq</i>-induced Phase Transformation of Ferrihydrite

Effects of rare earth elements on bacteria in rhizosphere, root, phyllosphere and leaf of soil\u2013rice ecosystem

The effects of rare earth mining on rice biomass, rare earth element (REE) content and bacterial community structure was studied through pot experiment. The research shows that the REE content in rice roots, shoots and grains was significantly positive correlated with that in soil, and the dry weight of rice roots, shoots and grains was highly correlated with soil physical and chemical properties, nutrient elements and REE contents; The exploitation of rare earth minerals inhibited a-diversity of endophytic bacteria in rhizosphere, root, phyllosphere and leaf of rice, significantly reduced the abundance index, OTU number, Chao, Ace index and also significantly reduced the diversity index–Shannon index, and also reduced uniformity index: Pielou’s evenness index, which caused β-diversity of bacteria to be quite different. The exploitation of rare earth minerals reduces the diversity of bacteria, but forms dominant bacteria, such as Burkholderia, Bacillus, Buttiauxella, Acinetobacter, Bradyrhizobium, Candida koribacter, which can degrade the pollutants formed by exploitation of rare earth minerals, alleviate the compound pollution of rare earth and ammonia nitrogen, and also has the function of fixing nitrogen and resisting rare earth stress; The content of soil available phosphorus in no-mining area is lower, and the dominant bacteria of Pantoea formed in such soil, which has the function of improving soil phosphorus availability. Rare earth elements and physical and chemical properties of soil affect the community structure of bacteria in rhizosphere and phyllosphere of rice, promote the parallel movement of some bacteria in rhizosphere, root, phyllosphere and leaf of rice, promote the construction of community structure of bacteria in rhizosphere and phyllosphere of rice, give full play to the growth promoting function of Endophytes, and promote the growth of rice. The results showed that the exploitation of rare earth minerals has formed the dominant endophytic bacteria of rice and ensured the yield of rice in the mining area, however, the mining of mineral resources causes the compound pollution of rare earth and ammonia nitrogen, which makes REE content of rice in mining area significantly higher than that in non-mining area, and the excessive rare earth element may enter the human body through the food chain and affect human health, so the food security in the REE mining area deserves more attention.

Two dimensional nanosheets as immunoregulator improve HIV vaccine efficacy.

Two-dimensional (2D) nanosheets as carriers have shown promising potential for surface-displaying or loading various drugs. Nevertheless, developing sheet-like materials themselves into an immunoregulator has never been realized so far. In this study, we take advantage of the immunoregulatory effects of rare earth elements themselves and develop water-soluble erbium–dysprosium 2D nanosheets (2D NSs). Such 2D NSs can target lymph nodes and activate macrophages to improve vaccine efficacy in mice significantly. Transcriptome analysis further reveals that six critical molecules (Msr1, Ccr2, Serpinb9, Klrk1, Klrd1, Klrc1) closely correlate with 2D NS-mediated immunoregulation in vivo. For the first time, the present work realizes a proof-of-concept for designing immunoregulatory 2D NSs and shows a promising potential of 2D NSs for improving the immunoprophylaxis/immunotherapy of vaccines.

Effects of Rare-Earth Elements on the Microstructure and Electrochemical Properties of As-Cast La0.6r0.15mg0.25ni3.5 (R = La, Pr, Nd, Gd) Alloys with Multiphase Structure

Effects of Rare-Earth Elements on the Microstructure and Electrochemical Properties of As-Cast La0.6r0.15mg0.25ni3.5 (R = La, Pr, Nd, Gd) Alloys with Multiphase Structure

Effects of Rare-Earth Elements on the Microstructure and Electrochemical Properties of As-Cast La0.6r0.15mg0.25ni3.5 (R = La, Pr, Nd, Gd) Alloys with Multiphase Structure

Effects of Rare-Earth Elements on the Microstructure and Electrochemical Properties of As-Cast La0.6r0.15mg0.25ni3.5 (R = La, Pr, Nd, Gd) Alloys with Multiphase Structure

Investigation of Environmental and Biological Effects of Rare Earth Elements (REEs) with a Special Focus on Industrial and Mining Pollutions in Iran: A Review

The present article is a review study on the types of rare earth elements (REEs), environmental and biological effects as well as the sources of emission of these elements as pollution in nature. The purpose of this study is to provide a vision in environmental planning and control of pollution caused by REEs. The evaluation of rare earth elements was studied in human life and its environmental and biological effects, which have particular importance and are entering the life cycle through industrial and mining pollution sources. Since mining activities intensify the dispersion of these elements in the environment and the existence of industrial factories located around urban drainage system plays a unique role in creating and spreading pollution caused by rare earth elements; As a result, two case studies were conducted on two mining and industrial areas. The first case is the Choghart mine in Yazd province as an example of mining pollution,and the second case study is performed on the Kor river as an example of industrial pollution which is caused by industrial activities around it, Then the results are well explained to show both two environments of litho and hydro. Due to this fact that produced environmental pollution can cause exchange pollutant compounds with the surrounding environment besides its long-lasting destructive effects; It can cause irreversible biological effects on living organisms. By targeting this evaluation, several techniques can be proposed to prevent the entry and dispersal of rare earth elements from pollution sources besides methods to reduce the damage of these elements to the ecosystem.

Investigating the toxically homogenous effects of three lanthanides on zebrafish

The adverse effects of rare earth elements (REEs) have been increasingly reported in the past decades and have raised concern about their environmental toxicities. However, the available data is insufficient to elucidate the toxic effects, mechanisms, and whether the toxicity across all REEs is uniform. In this study, zebrafish were exposed to 0, 0.8, 1.6, 3.2, 6.4, 12.8 and 25.6 mg/L Ln(NO3)3•6H2O to test the acute toxicity of La(III), Ce(III), and Nd(III). LC50 of the three lanthanides was compared to the extent of the impact on gene expression. We carried out the functionally grouped network-based transcriptome analysis using gene ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) to explore the molecular mechanisms. The acute toxicity test showed that LC50 of La(III), Ce(III), and Nd(III) were 2.53, 2.03, and 2.76 mg/L, respectively. Consistent with acute toxicity, Ce(III) caused a little more DEGs than La(III) and Nd(III). Some biological processes such as metabolism of xenobiotics, oocyte meiosis, steroid biosynthesis, DNA replication, and p53 signaling pathway were affected following exposure of all the three lanthanides. Ce(III) also induced changes in the chemokine-mediated signaling pathway. The results indicated that the lethality is comparable, and the toxic patterns are similar across the three lanthanides. This study gives comparative research on the toxicities of three lanthanides to model organism zebrafish.

The Re2Sn2O7 (Re = Nd, Sm, Gd) on the enhancement of fire safety and physical performance of Polyolefin/IFR cable materials

Polyolefin (PO) cables used in confined spaces need to have low smoke, low heat release, low toxic gas release and excellent physical properties. In this work, a series of rare earth stannates Re2Sn2O7 (RES, Re = Nd, Sm, Gd) with high temperature catalytic performance were prepared by hydrothermal method for synergistic flame retardant PO/IFR. The flame retardancy, heat release, smoke density, toxic gas release and physical properties of PO composites were thoroughly studied in detail. The RES could enhance the vertical burning rating and the limiting oxygen index (LOI) of PO/IFR composites. Moreover, the residual char of the thermogravimetric analysis increased from 9.7% to 11.4 wt% after the RES added in PO/IFR system. Interestingly, the PO/IFR system containing Gd2Sn2O7 exhibits the lowest peak heat release rate of 233.7 kW/m2. Excellent flame resistance due to the formation of a complete and compact protective char layer. In addition, the toxic release of PO during combustion is also effectively reduced by introducing the RES. The tube furnace combustion test shows that the emission of carbon oxide (CO) and hydrogen cyanide (HCN) of PO/IFR/Gd2Sn2O7 are the lowest. It can be attributed to the catalytic effect of rare earth elements and the blocking effect of the dense char layer. In addition, compared with the PO/IFR composites, the PO/IFR/RES system demonstrate higher mechanical properties and volume resistivity. Therefore, the addition of RES has a positive effect on improving the physical properties and fire safety properties of the PO/IFR cable composites, especially suitable for using in confined spaces.

Effect of rare-earth elements on microstructure and mechanical properties of in-situ Fe-TiB2 composites

By integrating stiff and light TiB2 particles into an iron matrix, the Fe-TiB2 composite provides a viable approach for lightweight structural material design. The Fe-TiB2 composites are fabricated by melting and casting with TiB2 particles produced in-situ by a pseudo-binary eutectic reaction during solidification. However, this results in coarsening of TiB2 particles and thus degrades the mechanical properties of the fabricated composites. In this study, Sm, Y, Gd, Nd, Ce, and La were added to hypereutectic Fe-TiB2 composites (Fe–10.35% Ti–18 at% B). The effects of the addition of different rare-earth (RE) elements on the microstructure and mechanical properties of the composites were studied. Alloying the composites with Sm, Y, Gd, Nd resulted in the coarsening of TiB2 primary particles in Fe-TiB2 composites while lowering their number density; however, it also reduced the eutectic spacing and size of the α-Fe grains. This reduced the average interparticle spacing, leading to marginally increased tensile strength and hardness. Furthermore, the addition of Ce and La significantly refined the TiB2 primary particles and scattered them into a more dispersive distribution while the eutectic spacing and size of the α-Fe grains decreased. Alloying with La, in particular, primarily reduced the interparticle spacing, resulting in a significant strengthening of mechanical characteristics. The La-added specimen reached an ultimate tensile strength (UTS) of up to 778.2 MPa and a hardness of up to 3.96 GPa, respectively 15.1% and 32.9% higher than that of the non-RE specimen.

Effect of rare earth elements and heat treatment process on microstructures and properties of 6016 aluminum alloy

The effects of different contents of rare earth elements (erbium (Er) and yttrium(Y) ) on the microstructures and properties of 6016 aluminum alloy have been investigated. The results indicate that Er and Y can refine the grain size of 6016 aluminum alloy, and the precipitation of the second phase increases obviously and most of them are distributed in the grain boundary; the hardness values of the as-cast, rolled, T4 and T4P samples with Er and Y are obviously increased, which can be improved by 10~30HV, and the effect of Er on hardness improvement is better than that of Y When both the addition mass fraction of Er and Y are 0.5%, the tensile property, work hardening coefficient and plastic strain ratio of aluminum alloy in T4P state are better, and they are respectively: 172.663MPa, 345.218MPa, 34.2%, 0.37, 0.79.

Effects of Rare Earth Elements on Blood Pressure and Their Exposure Biomarkers: Evidence from Animal Experiments.

Solid fuel combustion is an important source of the release of rare earth elements (REEs) into the ambient environment, resulting in potential adverse effects on human cardiovascular health. Our study aimed to identify reliable exposure biomarkers of REE intake and their potential role in blood pressure change. A total of 24 rats were administered with 14 REE chlorides at four doses (six rats per group). Fur samples were collected both before and after administration. Blood samples were collected after 12 weeks of REE intake. The REE concentrations in rat fur and blood samples were measured by inductively coupled plasma mass spectrometry. For each week, blood pressure, as well as heart rate and pulse pressure, were measured. The linear mixed-effect model was used to analyze the relationship between REE administration dose and blood pressure change. We found that the REE concentration in fur, but not blood, samples exhibited significant dose–response relationships with administration dose. It suggested that hair samples are a more efficient matrix for indicating the exposure level of a population to REEs than blood samples. However, there was no dose–response relationships between the administration dose and blood pressure change of rats, or with heart rate and pulse pressure for the 14 REEs. We also did not find a dose–response relationship between REE administration levels and plasma concentration of 8-hydroxy-2’-deoxyguanosine, as an important DNA oxidative stress damage biomarker. In conclusion, hair samples are more suitable as a sample type to reliably assess exposure to REEs than blood samples, and REEs did not have a direct adverse effect on blood pressure in our rat model.

Effects of rare earth elements on microstructure and tensile properties of Al-Si-Cu alloy at 250 °C

The effects of rare earth elements (La, Sm) on the high-temperature (250 °C) microstructure and mechanical properties of Al-Si-Cu alloys were analyzed. The experimental results show that with the addition of La and Sm, the α-Al was significantly refined, and the eutectic Si changed from acicular to rod-like and granular. XRD and SEM analysis shows that the rare earth phases in the alloy were mainly AlSiRe and AlRe. Fracture morphology observations show the fracture mode of the alloy changes from brittle and ductile fracture to ductile fracture. With the increase of La or Sm contents, the mechanical properties of the alloys at 250 °C increase at first, and then decrease. When the contents of La and Sm are 0.4wt.% and 0.2wt.%, the tensile strength of the alloy reaches maximum of 143.91 MPa and 201.48 MPa, respectively.

Promotion effect of rare earth elements (Ce, Nd, Pr) on physicochemical properties of M-Al mixed oxides (M\u2009=\u2009Cu, Ni, Co) and their catalytic activity in N2O decomposition

A series of M-AlOx mixed oxides (M = Cu, Co, Ni) with the addition of high loadings of rare earth elements (REE, R = Ce, Nd, Pr; R0.5M0.8Al0.2, molar ratio) were investigated in N2O decomposition. The precursors were prepared by coprecipitation and subsequent calcination at 600 °C. The obtained mixed metal oxides were characterized by X-ray diffraction with Rietveld analysis, N2 sorption, and H2 temperature-programmed reduction. Depending on the nature of REE and the initial M-Al system, R cations could be separately segregated in oxide form or coordinated with the transition metal cations and form mixed structures. The addition of Ce3+ consistently led to nanocrystalline CeO2 mixed with the divalent oxides, whereas the addition of Nd3+ or Pr3+ resulted in the formation of their respective oxide phases as well as perovskites/Ruddlesden–Popper phases. The presence of REE modified the textural and redox properties of the calcined materials. The rare earth element-induced formation of low-temperature reducible MOx species that systematically improved the N2O decomposition on the modified catalysts compared to the pristine M-Al materials by the order of Co > Ni > Cu. The Ce0.5Co0.8Al0.2 catalyst revealed the highest activity and remained stable (approximately 90% of N2O conversion) for 50 h during time-on-stream in 1000 ppm N2O, 200 ppm NO, 20 000 ppm O2, 2500 ppm H2O/N2 balance at WHSV = 16 L g−1 h−1.

Effects of rare earth elements doping on gas sensing properties of ZnO nanowires

The effects of rare earth elements (Ce, Eu, and Er) doping on the microstructure and gas sensing properties of ZnO nanowires were investigated. The Ce, Eu, Er-doped ZnO nanowires and pristine ZnO nanowires were synthesized via a solvothermal route. The structure of the prepared samples was studied and compared by X-ray diffraction, scanning electron microscopy, transmission electron microscopy, and X-ray photoelectron microscopy. The gas sensors were fabricated by coating the prepared samples on aluminum oxides tube-based Au sensing electrode, with Ni-Cr heating wire to control the operating temperature. The operating temperature of all sensors was determined to be 300 °C with consideration of ethanol response. At this temperature, all sensors showed good ethanol sensing performance, with the 1%Ce-doped ZnO nanowires-based sensor exhibited the highest ethanol response over the other sensors. The mechanism for the microstructure and gas sensing behavior difference of various samples was discussed.

Hypothetical Soil Thresholds for Biological Effects of Rare Earth Elements

Objectives: Anthropogenic exposures to rare earth elements are poorly known and there is limited information on their toxicity and ecotoxicity. At the same time, world production of rare earth elements has doubled every 15 years over the last half-century, and high environmental concentrations of gadolinium and lanthanum have already been found. The current review aims to give some estimates of overall exposures and an initial in-depth appraisal of thresholds for effects on agricultural soil. The results are envisaged to be used in initial assessments of agricultural soil where the natural concentrations have been anthropogenically enhanced.&#x0D; &#x0D; Methods: An extensive review has been made of available scientific literature. Criteria have been established for the selection and analysis of eligible research. For instance, only effects on soils with vegetation have been included in the assessment of biological effects. A species sensitivity distribution based on 25% inhibition of organism functions has been used to establish thresholds for effects on soil organisms. &#x0D; &#x0D; Results: Around the year 2000, mean anthropogenic contributions of lanthanides in European soil regions were at most a few per cent of the total soil content. Since then, they should have increased considerably. The proposed hypothetical threshold for agricultural soils is 1125 mg total rare earth element per kg of soil. This threshold is about 8 times the natural soil concentration.&#x0D; &#x0D; Conclusions: If this result holds up to scrutiny, it implies that general anthropogenic pollution by rare earth elements will not be a threat to agricultural sustainability for the coming generation. A preliminary assessment suggests that this threshold would also protect humans from adverse effects due to secondary exposure.

Effects of Y and Addition of Refiners on Hot Tearing Susceptibility of MgZn-Based Alloy

On the basis of studying the effect of rare earth elements on hot tearing susceptibility (HTS) of Mg–Zn alloys, further exploring effective ways to reduce HTS of Mg–Zn–Y alloys are very important for the development and application of magnesium alloys. In this paper, the effects of 2 at% Y on HTS of MgZn1 alloy and several grain refiners on HTS of MgZn1Y2 alloy were studied. The modified Clyne–Davies model is used to predict the HTS of the investigated alloys, which are found in the descending order: MgZn1 > MgZn1Y2 > MgZn1Y2–0.5 wt% Na2CO3 > MgZn1Y2–0.5 wt% Ti > MgZn1Y2–0.5 wt% Zr. By means of XRD, SEM, TEM and EBSD, the evolution of the microstructure during solidification is revealed. The results show that the addition of 2 at% Y can not refine α-Mg grains, but it can change the precipitation type of the second phase. When the precipitation type of the second phase changes from Mg7Zn3 to Mg12ZnY (LPSO phase) and Mg3Zn3Y2 (W-phase), the solidification end temperature of the alloy increases by more than 100 °C, and the coherent lattice of LPSO and α-Mg has a better bridging effect on the grain boundary, which reduces the HTS by 28.4%. Moreover, the addition of 0.5 wt% Na2CO3, 0.5 wt% Ti or 0.5 wt% Zr is an effective method for α-Mg grain refinement, equiaxation and dendrite coherent delay of MgZn1Y2 alloy. In particular, the addition of 0.5 wt% Zr can reduce the α-Mg grain size of MgZn1Y2 alloy by 89.1% and increase the solid fraction by 45% when dendrites are coherent, which results in a 77.1% reduction in HTS.

Responses of ramie (Boehmeria nivea L.) to increasing rare earth element (REE) concentrations in a hydroponic system

A number of studies have focused on the effects of rare earth elements (REEs) on crop plants, while little attention has been paid on how tolerant plant species respond to increasing mixed REE concentrations. In this study, ramie (Boehmeria nivea L.) was exposed to a series of REE concentrations prepared with equimolar mixtures of 16 REEs (i.e. 0, 1.6, 8, 16, 80, 160, 400, 800 μmol/L) in order to explore REE accumulation and fractionation characteristics in ramie and the responses of this plant to mixed REEs. Results show that ramie root and shoot biomasses are unaffected under lower REE concentrations (1.6–80 μmol/L), while the growth of ramie and the uptake of nutrients especially Ca and Mn are largely inhibited under higher REE concentrations (160–800 μmol/L). The P and Mo concentrations in the roots increase with the increasing REE concentrations in the solution, suggestive of an involvement of P and Mo in dealing with the high concentrations of REEs in this plant. The preferential uptake of Ce and heavy REEs (HREEs) and the preferential transport of HREEs within the plant lead to a positive Ce anomaly and a HREE enrichment in ramie leaves. Our study suggests that ramie could be a good candidate for the phytoremediation of heavily REE-contaminated soils (e.g., REE mine tailings in southern China). Our results also shed light on points of taking into account phytoremediation management strategies of REE-contaminated soils (e.g., P and Mo fertilization).

Martensite phase structure of Mg-Sc lightweight shape memory alloy and the effect of rare earth elements doping

With the continual increase of application requirement of lightweight shape memory alloys (SMAs), MgSc alloys have drawn great attention as a new SMA. However, the ambiguous martensitic structure, unclear transformation path, and low martensitic transformation temperature (Tm) of Mg-Sc alloys are still issues. Herein, the martensitic structure and transformation path of Mg-Sc alloys were investigated systematically. The martensite phase was identified finally to be an orthorhombic structure by formation energy. Moreover, to improve the Tm, the effect of rare earth elements doping on Tm was studied, and Tm was increased by 28.2 K with 1.25 at.% Gd doping. The total density of states indicated that the phase stability determined the increase of Tm. Furthermore, the partial density of states indicated that the d orbital electrons coupling between Sc and Gd atom led to the changing of Tm. Our results provide a firm base for designing the new Mg-Sc-based lightweight SMAs.