Rare Earth Resources Research Articles

Unraveling the New Role of an Ethylene Carbonate Solvation Shell in Rechargeable Metal Ion Batteries

This work is supported by the National Natural Science Foundation of China (21978281, 21975250) and the National Key R&D Program of China (SQ2017YFE9128100). The authors also thank the Independent Research Project of the State Key Laboratory of Rare Earth Resources Utilization (110005R086), Changchun Institute of Applied Chemistry, Chinese Academy of Sciences. The research was also supported by King Abdullah University of Science and Technology (KAUST) and Hanyang University.

Concentration Mechanisms of Rare Earth Element-Nb-Zr-Be Mineralization in the Baerzhe Deposit, Northeast China: Insights from Textural and Chemical Features of Amphibole and Rare Metal Minerals

AbstractThe Early Cretaceous Baerzhe deposit in Inner Mongolia, Northeast China, hosts a world-class resource of rare earth elements (REEs), niobium, zirconium, and beryllium. In contrast to previous interpretations of the deposit as a multiphase, miaskitic alkaline granite, our observations of the relationships of various rock phases, the textural features and chemical evolution of amphibole, and the distribution of primary and secondary mineral assemblages suggest that the igneous phases evolved from a hypersolvus porphyritic granite, through a variably altered transsolvus granite, both of which are miaskitic, to a strongly altered, agpaitic, transsolvus granite that contained primary elpidite. All of these phases share a common igneous lineage. The Baerzhe deposit is characterized by five stages of rare metal mineralization, starting with the magmatic crystallization of elpidite (stage I). Elpidite was subsequently hydrothermally replaced by zircon and quartz to form pseudomorphs in stage II. Stage II is also characterized by Na metasomatism (albite and aegirine alteration of alkali feldspar and amphibole, respectively) and by snowball quartz that contains inclusions of albite, aegirine, and zircon. Sodium metasomatism, Zr mineralization, and snowball quartz are restricted to the agpaitic rocks. REEs, Nb, and Be occur as a variety of minerals that are disseminated through all the altered rocks and were precipitated in three sequential stages (stages III-V), with the formation of heavy REE-dominant phases generally preceding light REE-dominant phases. Moderate to pervasive hematization, which altered much of the transsolvus miaskitic granite and all the agpaitic granite, initiated late in stage II and accompanied most of the REE-Nb-Be mineralization in stage III. The stage-III mineralization, represented by hingganite-(Y), hingganite-(Ce), aeschynite-(Y), and columbite-(Fe), developed in two substages, with hingganite-(Y) preceding hingganite-(Ce); these REE-Nb-Be minerals are mainly contained in quartz-rich pseudomorphs (REE-Nb-Be–rich pseudomorphs) but also occur as partial replacement of earlier minerals. Stages IV and V represent a transition from F-absent assemblages that are characterized by euxenite-group minerals and monazite-(Ce) in stage IV-A, to light REE and F-rich minerals: bastnäsite-(Ce) in stage IV-B and fluocerite-(Ce) and synchysite-(Ce) in stage V. The low REE, Nb, and Be concentrations in amphibole and the fact that REE-Nb-Be assemblages never contain zircon as a constituent preclude leaching of preexisting amphibole or zirconosilicates as significant sources of REEs, Nb, or Be. Rather, these elements may have inherently been present in magmatic-hydrothermal fluids or have been leached from crystallized fluoride melts.

Optimization of Nitric Acid Leaching of Rare Earth Elements From Moroccan Natural Phosphate

Phosphate is a very important natural resource in Morocco and one of the secondary resources of rare earth elements. Our study is particularly interested in Youssoufia phosphate, which contains 228.77 ppm of rare earth elements (ΣREEs). The purpose of our work is to study the influence of different parameters (acid concentration, solid/liquid ratio and temperature) in order to determine the optimal conditions for the leaching of rare earths. An experimental design (Doehlert matrix) has been drawn up to optimize the experimental conditions of the leaching. All tests were made with nitric acid at different concentrations varying between 1.5M and 4.5M with a solid/liquid ratio of 1/12 to 1/6; reaction temperature and duration are respectively 20°C to 80 °C and 60 min. The optimal conditions are obtained when using 69 °C as temperature, 4.1 M as acid concentration and 1/9 as solid/liquid ratio.

Enhanced fluorescence achieved by introducing benzoic acid as coligand onto Tb3+ grafted PAN nanofibers

Abstract Coordination effect between C N groups of polyacrylonitrile (PAN) and rare earth ions is adopted to graft Tb3+ ions onto the surface of electrospun PAN nanofibers. Benzoic acid (BA) is introduced as a coligand to improve the fluorescence properties of the products. The products are tested by scanning electron microscopy, Fourier transform infrared spectroscopy, UV–Vis absorption spectroscopy and fluorescence spectroscopy. The effects of concentrations of Tb3+ and BA, and reaction time on products’ properties are studied. The results show that Tb3+ ions could be successfully grafted onto PAN nanofibers, but the fluorescence intensity of the resulting PAN@Tb3+ nanofibers is very weak. By contrast, the fluorescence intensity of PAN@(Tb3+/BA) nanofibers is significantly stronger than that of PAN@Tb3+ nanofibers after BA is introduced as the coligand, and meanwhile, the concentration quenching effect of Tb3+ ions is effectively inhibited. In addition, PAN@(Tb3+/BA) nanofibers are superior in structure, which not only effectively utilize the precious rare earth resources, but also ensure high mechanical strength. The novel products are expected to be used in fields such as fluorescent nanoscale devices and fluorescent probe technique.

Phase structure and magnetic properties of La/Ce substituted nanocomposite SmCo5/α-Fe magnets prepared by high energy ball milling and subsequent annealing

The phase structures and magnetic properties of isotropic nanocomposite permanent magnetic materials with the nominal composition of (Sm1-xRx)Co5 (x = 0, 0.25, 0.5, 0.75, 1; R = La, Ce) + 25 wt% α-Fe prepared by high-energy ball milling and subsequent annealing have been investigated systematically. It is found that the phase structure of La-doped nanocomposite magnets is quite different from that of the Ce- doped. The hard phase of Ce-doped nanocomposite magnet is 2:7 phase and unchangeable with increasing the Ce content and annealing temperatures (≤650 °C), while that of La-doped nanocomposite magnets undergoes a phase transition from 2:7 phase to 1:7 and 2:17 hard phases with increasing the La content and annealing temperatures. Both magnetic performance of La and Ce doped nanocomposite magnets shows a tendency to decrease as La or Ce content increases. The analysis of hysteresis loop reveals that both La and Ce doped nanocomposite magnets exhibit the strong ferromagnetic exchange coupling between hard and soft magnetic phases. Surprisingly, the magnetic performance of La-doped SmCo5/a-Fe is much superior to that of the Ce-doped although the Ce-doped Sm-Co hard phase has a relatively higher intrinsic magnetic property. The mechanism behind is found to be related to the change of Fe soft phase after adding La. Our results demonstrate that the substitution of Sm by La instead of Ce can produce the high-performance and low-cost SmCo5/a-Fe nanocomposite magnets. Our study is of significance to balance the utilization of the rare-earth resource.

Ecological environment quality evaluation and evolution analysis of a rare earth mining area under different disturbance conditions.

The negative impacts of the overexploitation of resources on regional environments have become increasingly obvious. The contradiction between the environment and development and the management of the ecological environment in mining areas are urgent problems to be solved. This paper uses Landsat images from four temporal phases from 1991 to 2018 in the Lingbei mining area of Dingnan County, China, to construct a rare earth remote sensing-based ecological index (RE-RSEI) suitable for rare earth mining areas and to analyze the impacts of different rare earth mining methods, mining scales and environmental management measures on the mining area environment over the past 27years. The results show that since 1991, due to the mining techniques of "pond leaching" and "heap leaching" and the soil condition, mining has caused severe damage to the land and vegetation, and the ecological environment quality of the entire mining area has been seriously reduced with its RE-RSEI value dropping from 0.744 to 0.675. After 2010, through the optimization of mining technology and the government's attention to ecological environmental governance, the quality of the ecological environment was slowly restored, and the recovery effect at some mine sites was remarkable. The RE-RSEI model has good applicability to rare earth mining areas, can intuitively reflect the destruction and restoration of the ecological environment of rare earth mining areas under different mining modes, and provides scientific guidance for promoting the coordination of the development and utilization of rare earth resources and mine ecological environmental protection and sustainable development.

Mining and Restoration Monitoring of Rare Earth Element (REE) Exploitation by New Remote Sensing Indicators in Southern Jiangxi, China

Rare earth elements (REEs) are widely used in various industries. The open-pit mining and chemical extraction of REEs in the weathered crust in southern Jiangxi, China, since the 1970s have provoked severe damages to the environment. After 2010, different restorations have been implemented by various enterprises, which seem to have a spatial variability in both management techniques and efficiency from one mine to another. A number of vegetation indices, e.g., normalized difference vegetation index (NDVI), soil-adjusted vegetation index (SAVI), enhanced vegetation index (EVI) and atmospherically resistant vegetation index (ARVI), can be used for this kind of monitoring and assessment but lack sensitivity to subtle differences. For this reason, the main objective of this study was to explore the possibility to develop new, mining-tailored remote sensing indicators to monitor the impacts of REE mining on the environment and to assess the effectiveness of its related restoration using multitemporal Landsat data from 1988 to 2019. The new indicators, termed mining and restoration assessment indicators (MRAIs), were developed based on the strong contrast of spectral reflectance, albedo, land surface temperature (LST) and tasseled cap brightness (TCB) of REE mines between mining and postmining restoration management. These indicators were tested against vegetation indices such as NDVI, EVI, SAVI and generalized difference vegetation index (GDVI), and found to be more sensitive. Of similar sensitivity to each other, one of the new indicators was employed to conduct the restoration assessment of the mined areas. Six typically managed mines with different restoration degrees and management approaches were selected as hotspots for a comparative analysis to highlight their temporal trajectories using the selected MRAI. The results show that REE mining had experienced a rapid expansion in 1988–2010 with a total mined area of about 66.29 km2 in the observed counties. With implementation of the post-2010 restoration measures, an improvement of varying degrees in vegetation cover in most mines was distinguished and quantified. Hence, this study with the newly developed indicators provides a relevant approach for assessing the sustainable exploitation and management of REE resources in the study area.

Progress in developing the novel extractants for rare earths

<p indent=0mm>The separation of rare earths is the key joint between the rare earth resources and high-performance functional materials of rare earth. Because most rare earth products were produced by solvent extraction, the performance of extractants is crucial to the efficiency of the extraction and separation of rare earths. In this review, the progress in the development of novel extractants for rare earths in China in the past ten years is briefly reviewed with more attention on the work on dialkyl phosphinic acids (including symmetric- and asymmetric ones), amine-containing organophosphorous extractants and carboxylic acids.

A DPSIR-TODIM Model Security Evaluation of China’s Rare Earth Resources

Rare earth is an important strategic mineral resource for national economy and national security. As the largest producer and exporter of rare earth, China’s rare earth industry has problems associated with excessive production, mismatched pricing power and environmental pollution. Therefore, an in-depth study of the rare earth industry security is necessary. Based on proposed definition for mineral resource security, this paper established a rare earth resource security evaluation model based on the “driver-pressure-state-impact-response” conceptual model using an extended TODIM (an acronym in Portuguese for interactive and multi-criteria decision-making) method combined with the E-DEMATEL (entropy and decision-making trial and evaluation laboratory) method. The model was then applied to Chinese rare earth data from 2006–2015 to assess the security, from which it was found that while the security level was not high, the overall trend was improving. Moreover, some critical response factors affecting REEs (rare earth elements) security are identified, including tariffs, research investment, etc. This paper not only introduces a new evaluation of REEs security but also explores the crucial indicators and the response mechanism.

Rare earth elements deposits in China: Spatio-temporal distribution and ore-forming processes

<p indent=0mm>China dominates the world REE (rare earth elements) resources, 98% of which are from carbonatite-related REE deposits. Extensive studies of this type of REE deposits are available, but it is still poorly understood how carbonatite magmas were generated and how REEs were transported and precipitated in such magmas. On the basis of previous studies, this paper synthesizes the spatio-temporal distribution of this type of REEs deposits in China and their major features, including characteristics of ore-forming fluids, and discusses existing genetic models regarding the origin of causative magma, and mechanics of REE enrichment, transportation and precipitation. In China, carbonatite-related REE deposits occur in the craton margin environments with four major REE metallogenic belts: the Mesoproterozoic Bayan Obo-Langshan belt (e.g., the Bayan Obo deposit), the early Mesozoic eastern Qinling-Dabie belt (e.g., the Miaoya deposit), the late Mesozoic Zibo-Laiwu-Weishan belt (e.g., the Chishan deposit), and the Cenozoic Mianning-Dechang belt (e.g., the Maoniuping deposit). In these belts, REE-hosting carbonatites were emplaced in continental rift zones or along large-scale strike-slip faults at the Precambrian craton margins. The causative magmas were originated from partial melting of enriched lithospheric mantle sources, which may have undergone metasomatism by subducted slab-related fluids/melts, and may have also asthenospheric material involvement. These magmas may have formed through melt immiscibility and fractional crystallization from primary carbonated silicate melt. The melt immiscibility may include unmixing between alkaline silicate and carbonate melts, or multi-phase melt immiscibility of carbonate melt, mafic or ultramafic melt, phosphomagnesite melt, and alkaline silicate melt. The immiscibility and/or crystal fractionation of mafic mineral can lead to the formation of carbonate melts rich in REEs. The newly discovered lithofacies zonation at Bayan Obo, with a biotitite outer zone, implies a magmatic evolution of a silica-rich parent magma. The low REE concentrations and LREE/HREE ratios of biotitite indicate possible LREE enrichment in the evolved carbonatite magma by biotite fractional crystallization. The crystallization of carbonate minerals during the upwelling and emplacement of carbonatite magmas, may further enrich late-stage carbonatite melts and carbonatite fluids in LREE. This process can better explain the REE mineralization dominantly in the late-stage of carbonatite magmatism or post-magmatic fluid stage. The melt, melt-fluid and fluid inclusion results for Bayan Obo, Maoniuping and Chishan indicate SO₄²⁻ and CO₂-rich carbonatite fluids. The microthermometry and SEM/EDS results for primary melt-fluid inclusions hosted in fluorite from Maoniuping indicate that carbonatite fluids were extremely rich in SO₄²⁻, and underwent an unmixing process between sulfate melt and aqueous fluid. Both inclusion and experimental results indicate that the sulfate has a very high solubility in SiO₂-bearing aqueous fluids, inconsistent with the SiO₂-free system. The geochemical thermodynamic results also confirm the SO₄²⁻ -dominated agent for REE transportation. The unmixing process between sulfate melts and aqueous fluids would lead to extensive decrease of SO₄²⁻ in the fluid, and bulk REE precipitation. The rapid evolution of carbonatite fluids prevents long distance migration of carbonatite fluids, resulting in all REE mineralization within, or proximal to the carbonatite bodies. The strong mineralization would occur in the central zone or the shallow level and then would become weaker outwards and downwards of carbonatite bodies.

Data-driven analysis for source apportionment and geochemical backgrounds establishment of toxic elements and REEs in the Tohoku region, Japan

The Tohoku region of Japan is geologically diverse, with a long agriculture and mining history; however, little information about the origins and distribution mechanisms of elements in this region has been reported. This study aims to provide fundamental insights into the effects of geological features and anthropogenic activities on various elements, including toxic elements and rare-earth elements (REEs), in the Tohoku region. A geochemical database (2007, AIST) consisting of data for 53 elements in 485 river sediment samples from the region was used, and a data-driven method combining principal component analysis (PCA) was applied for analysis. GBs for numerous types of areas, including general areas (GGB), natural environments (NGB), high anthropogenic-influenced areas (AGB) and mineralised areas (MGB) were established; especially, MGB was newly proposed in this study to illuminate the role of ore deposits. Both PCA and GBs comparison results show that geological features (especially igneous rock distribution) were the most important factor affecting elemental distribution, rather than anthropogenic activities. In the PCA, the first principal component showed that REE resources were commonly associated with the distribution of granitic rocks and REE-bearing minerals. Anthropogenic contaminations from mining, urban, and anthropogenic areas played important roles as the origin of some toxic elements (e.g. Ni, Pb, Sb). Comparisons between these GBs effectively elucidated the enrichment of certain toxic elements (e.g., Hg, Sb) in ore deposit areas. This data-driven study not only clarified the origins of toxic elements, but also revealed the location of potential REE mineral resources in the Tohoku region.

The occurrence characteristics and recovery potential of middle-heavy rare earth elements in the Bayan Obo deposit, Northern China

The Bayan Obo deposit is a world-class Fe-REE-Nb deposit, and its reserves of rare earth element (REE) resources rank the first over the world. In the face of the current situation of insufficient utilization rate of rare earth resources and scarcity of middle-heavy rare earth elements (M−HREE) resources, the Bayan Obo deposit with such a huge amount of M−HREE cannot be underestimated. In this paper, the occurrence characteristics of M−HREE in different types of iron ore in the Bayan Obo main ore body are studied by using field emission scanning electron microscope (FESEM), energy dispersive spectrometer (EDS) and advanced mineral identification and characterisation system (AMICS), and the enrichment mechanism is also discussed. The results show that both Sm and Y are the most abundant M−HREE in each type of iron ore in the main ore body, and the content of M−HREE accounts for 1.41%–5.57% of total REE, among which the content of M−HREE in aegirine type Nb-REE-Fe ore (824.47 ppm) and fluorite type Nb-REE-Fe ore (794.82 ppm) are higher, and the content of M−HREE in massive type Nb-REE-Fe ore is lower (318.49 ppm). The main minerals containing M−HREE are bastnasite, parisite, Huanghoite, monazite, aeschynite and fergusonite, among which the content of M−HREE in fergusonite and aeschynite are the highest. According to the characteristics of mineral paragenetic association of REE in this ore district, it is believed that the REE migrates mainly in many different forms of complexes. Heavy rare earth elements (HREE) mainly experienced carbonatite magmatism stage, sodium-fluorine metasomatism stage and late vein mineralization stage, and finally got enrichment.

Rare Earth Elements Occurrence and Economical Recovery Strategy from Shale Gas Wastewater in the Sichuan Basin, China

Global demand for rare earth elements (REEs), which are central to many modern high-tech industries, is increasing rapidly. For the first time, we discovered and determined the REEs concentrations in Sichuan Basin shale gas flowback and produced water (FPW). The total REEs in shale gas FPW investigated in this work ranged from 4.5 to 118.3 μg/L. Europium (Eu) was found in all samples (0.92–79.62 μg/L). Our study suggests that there was approximately 4.2 tons of Eu2O3 in FPW worldwide in 2016, and that this value could increase to 16.8–111.7 tons in 2030. We discussed potential methods for Eu recovery from FPW and further research needs to facilitate recovery of REE. The results suggest that wastewater from oil and gas extraction constitutes a promising resource for REEs, especially for Eu.

Geochemistry of the Heavy Mineral Sands from the Garampeta to the Markandi beach, southern coast of Odisha, India: Implications of high contents of REE and Radioelements attributed to Placer Monazite

This study presents major element, radioactive element and rare earth element (REE) concentrations of the Garampeta to Markandi beach along the southern coast of Odisha, India to delineate the source signature and resource potential of the beach placer deposits. Average ∑REE concentration of the beach sand samples is about four times higher than the average crustal concentration. The LREE concentration is higher than HREE, with a pronounced negative europium anomaly. The study also discusses about the radioelement 238U, 232Th and 40K concentrations in the study area, and their relationship with REE. Weathering condition of the source rock, based on the major elements and Th/U ratio indicated a reasonably high degree of weathering. Major element and the REE composition along with the europium anomaly, relate the beach placers to mainly charnockite and khondalite source. An elevated level of thorium (> 60 times than the average UCC values) as exhibited by the samples could be attributed due to the presence of monazites. The high concentration of REEs like Nd and Dy along with La and Ce indicates significant REE resource potential in the beach placers which is important for the resource potential in terms of the strategic mineral reserves of the country.

Phase equilibria in the CaO-La2O3-Nb2O5 system at 1823, 1773, and 1673 K

ABSTRACT Phase equilibria in the CaO-La2O3-Nb2O5 system are of great significance for the utilization and application of rare earth and Nb resources. In the present work, the phase equilibria in high w(Nb2O5) corner of the CaO-La2O3-Nb2O5 system were studied by high-temperature equilibrium and quenching technology. Based on the continuity of phase diagram, a “Concavity and Convexity Rule” was proposed to predict the reasonable range of the unknown liquidus line. Finally, the isothermal sections and liquidus projection of the CaO-La2O3-Nb2O5 phase diagram were constructed, which include the primary phase fields of CaNb2O6, LaNbO4, Ca2Nb2O7, (Ca, Nb, La)O, and related liquidus lines at 1823, 1773, and 1673 K. Moreover, the subsolidus phase field of (Ca, Nb, La)O-LaNbO4-Ca2Nb2O7 with peritectic nonvariant reaction and CaNb2O6-LaNbO4-Ca2Nb2O7 with eutectic nonvariant reaction were determined, respectively.

A comparison of global rare earth element (REE) resources and their mineralogy with REE prospects in Sri Lanka

Rare earth elements (REEs), a group of 17 elements comprises 15 lanthanides, scandium and yttrium, are largely attracting the world’s attention due to their importance in a wide variety of advanced technological applications. Global REEs production is mainly sourced from resources, such as carbonatites, alkaline igneous rocks, placers, laterites, and ion-adsorption clays. Recently, REE demand has been escalating, especially due to the REE applications in renewable energy and defense sectors, expecting a worldwide shortage of REE supply in the future. Therefore, REEs have been widely accepted as strategic elements in the world, which compels to prospect for new and alternative REE resources. In this context, Sri Lanka has a favorable geological setting which implies the presence of REE mineralization. Previous geochemical studies in Sri Lanka have reported significant concentrations of REEs in different geological formations and mineral resources. Accordingly, Pulmoddai and other beach placer deposits, Eppawala carbonatite, alluvial placer deposits, and pegmatites have been identified as potential REE resources in Sri Lanka. Monazite, apatite, allanite, and zircon are the primary rare earth (RE) minerals found in the preceding resources. The Pulmoddai mineral sand deposit is considered as the most potential REE resource in the island, which is enriched in monazite containing more than 61% of light rare earth elements (LREEs). Similarly, Eppawala carbonatite contains high concentrations of LREEs. However, despite their significant REE enrichments, to date, no attempt has been made to recover these REE prospects, which essentially conceals their potential of catering for both local and global REE supply chains.

Effect of Ce and La Substitution on the Microstructure and Magnetic Properties of Hot-deformed Nd-Fe-B Magnets

Nd in hot-deformed Nd-Fe-B magnets was partially substituted by Ce and La for the purpose of reducing the materials cost and balancing the utilization of rare earth resources. Initial melt-spun ribbons with the nominal compositions of (NdSUB1-x/SUBMSUBx/SUB)SUB13.6/SUBFebalBSUB5.6/SUBGaSUB0.6/SUBCoSUB6.6/SUB (x = 0, x = 0.2/M=Ce, x = 0.3/M=Ce, Ce+La, wt.%) were prepared by a single-roller melt-spinning method, and pulverized into powders. The powders were then hot-pressed at 973 K under 100 MPa, and deformed at 973 K until 75 % of height reduction was achieved. The magnetic properties of hot-deformed magnets were decreased with the substitution of Ce for Nd. In addition, simultaneous substitution of Ce and La for Nd resulted in much lower magnetic properties. This tendency was almost the same as initial melt-spun powders. The deterioration on magnetic properties by substation of Ce and La for Nd in hot-deformed Nd-Fe-B magnets could be attributed to not only inferior intrinsic properties of (Ce/La)₂FeSUB14/SUBB to Nd₂FeSUB14/SUBB phase but also the effect of Ce/La substitution on microstructure such as density and grain alignment during hot-deformation. Although the magnetic properties were deteriorated by substitution of Ce and La for Nd in hot-deformed Nd-Fe-B magnets, the cost performance was largely enhanced from 2.32 to 2.62 MGOe×kg/$ by 13 % when increasing the content of Ce substituted for Nd from 0 to 0.3 wt.%.

Effects of rice straw and rice straw ash on rice growth and \u03b1-diversity of bacterial community in rare-earth mining soils

Pot experiments were carried out to study the effects of rice straw (RS) and rice straw ash (RSA) on the growth of early rice and α-diversity of bacterial community in soils around rare earth mining areas of Xunwu and Xinfeng counties in South Jiangxi of China. The results showed that the exploitation of rare earth resources leads to soil pollution around rare earth mining areas and affects the growth of rice, and the content of rare earth elements (REEs) in rice was positively correlated with that in soils and negative correlated with dry weight of rice; The addition of RS to soils around REE mining area can inhibit growth of early rice, and the dry weight of rice grains, shoots, roots is lower when compared with the controls, while the content of REEs is higher. The α-diversity of soil bacterial decreases, which promotes the growth of Pseudorhodoferax, Phenylobacterium and other bacteria of the same kind, and inhibits the growth of beneficial bacteria. The addition of RSA to soils had no significant effect on α-diversity of soil bacterial but promoted the growth of Azospira and other beneficial bacteria, inhibited the growth of Bryobacter and other bacteria of the same kind, significantly improved the dry weight of grains, shoots and roots of early rice, and reduced the content of REEs in these parts of rice. It can be concluded that RS is unsuitable to be added to the planting soil of early rice in REE mining area, while RSA is suitable.

Economic Loss Dynamics of Rare Earth Industry along the Yellow River: Taking Renewable Energy Accounting as an Observation Indicator

Qian, A.; Zhu, X., and Wang, F., 2020. Economic loss dynamics of rare earth industry along the Yellow River: Taking renewable energy accounting as an observation indicator. In: Yang, Y.; Mi, C.; Zhao, L., and Lam, S. (eds.), Global Topics and New Trends in Coastal Research: Port, Coastal and Ocean Engineering. Journal of Coastal Research, Special Issue No. 103, pp. 101–106. Coconut Creek (Florida), ISSN 0749-0208.The environmental pollution and ecological destruction caused by the exploitation of raw materials in the renewable energy industry is a neglected topic at present. Poor environmental management is one of the important reasons for the ecological damage of renewable energy projects. Rare earth resources are the main raw materials for renewable energy, and their production and mining mainly take place in China. According to Chinese government, the pollution caused by rare earth was most obvious between 1992 and 2010 and mainly happened in Baotou, which contributed 80% of global rare earth production. Therefore, this paper will combine the development of renewable energy before 2009 to demonstrate the pollution of China's rare earth mining areas. Based on the Input-Output Table developed by the European Union, by using multi-country input-output model to study the renewable energy consumption. It is found that, in rapid development period of renewable energy, the smaller the gap between global supply and demand, the greater the degree of exploitation in production areas, and the greater the ecological degradation. Based on 2019 IRNEA's forecast, our paper holds that the global renewable consumption can be used as a more intuitive indicator for the government to evaluate the economic loss level caused by the rare earth industry.

Selective preparation of neodymium phosphates from iron mixed solution by two-step precipitation

Abstract Neodymium iron boron alloy, Nd2Fe14B, is used in the manufacture of magnets. Neodymium is one of the rare earth elements, so it is valuable and expensive. In order to protect this rare earth resource, it is required to collect, reuse, and recyle rare earth elements. Recently, a new method for recovering neodymium phosphate from mixed solutions has been reported, avoiding the difficulties reported by previous methods. Since rare earth phosphate is the main component of rare earth ore, this new phosphate process was proposed. Neodymium phosphate was precipitated selectively from iron-neodymium mixed aqueous solution by 2 step processes with pH adjustments in this work. With this method, it was possible to separate neodymium and iron without using high temperatures or specialized equipment. The optimum conditions were determined by evaluating precipitation by yield, Fe/Nd ratio, hue, UV–visible reflectance spectra, X-ray diffraction, and infrared spectroscopy. In step I where pH was adjusted using sodium hydroxide, iron hydroxide was precipitated. Then, phosphoric acid was added, and the pH was further adjusted to obtain a neodymium phosphate precipitate as step II. The optimum conditions of this separation method were clarified.