Search Results (71)

Rare earth elements (REE) are vital for renewable energy, electronics, and advanced technologies; however, the process-related evolution of REE research has not been systematically quantified. This study conducts the first large-scale bibliometric analysis of 76,768 REE-related publications (1975–2024) from Web of Science, using the Cross-Disciplinary Publication Index (CDPI) and Technology–Economic Linkage Model (TELM). Results reveal three development phases: publication growth from <300 (1975–1990) to >5000 after 2008, driven by China’s export restrictions and the global clean energy transition; China leads with 24.1% of publications, followed by the U.S. (11.7%) and Germany (6.4%). Interdisciplinary mapping identifies materials science as the central field (CDPI = 0.81) linked to nanotechnology (0.75) and environmental science (0.66). Four thematic clusters dominate: (i) deposit geology, (ii) material applications, (iii) green extraction technologies, and (iv) circular economy strategies. Recent emphasis on sustainable practices and unconventional sources—such as phosphorites, bauxite, coal fly ash, and urban mining—reflects a shift toward green innovation. The findings guide policies to diversify REE supply through unconventional deposits (~50 Mt coal-hosted REE), eco-friendly extraction, and recycling. Future priorities include AI-driven exploration, lifecycle assessment of secondary sources, and stronger global collaboration to secure resilient, sustainable REE supply chains. Full article

Apatite is a key indicator mineral whose chemical signature can reveal the genesis and evolution of ore-forming systems. However, correctly interpreting these signatures requires a robust discrimination between apatite types formed by different geological processes, such as metamorphism and hydrothermal activity. This study aims to chemically characterize and genetically classify apatite samples from the Slyudyanka deposit (Siberia, Russia) to establish discriminative geochemical fingerprints for metamorphic and hydrothermal apatite types. We analyzed 80 samples of apatite using total reflection X-ray fluorescence (TXRF) and inductively coupled plasma mass spectrometry (ICP-MS). The geochemical data were processed using principal component analysis (PCA) and k-means cluster analysis to objectively discriminate the apatite types. Our analysis reveals three distinct geochemical groups. Metamorphic veinlet apatite is defined by high U and Pb, low REE, Sr, and Th, and suprachondritic Y/Ho ratios. Massive metamorphic apatite from silicate–carbonate rocks shows extreme REE enrichment and chondritic Y/Ho ratios. Hydrothermal–metasomatic apatite features high Sr, Th, and As, with intermediate REE concentrations and chondritic Y/Ho ratios. Furthermore, we validated the critical and anomalous Y concentrations in the metamorphic veinlet apatite by cross-referencing TXRF and ICP-MS data, confirming the reliability of our measurements for this monoisotopic element. We successfully established diagnostic geochemical fingerprints that distinguish apatite formed in different geological environments at Slyudyanka. The anomalous Y/Ho ratio in metamorphic veinlet apatite serves as a key discriminant and provides insight into specific fractionation processes that occurred during the formation of phosphorites in oceanic environments, which later transformed to apatites during high-grade metamorphism without a change in the Y/Ho ratio. This work underscores the importance of multi-method analytical validation for accurate geochemical classification. Full article

This study reports the discovery of a newly identified phosphorite deposit in the Al-Tafeh area of northern Jordan. Geological fieldwork investigated three outcrops and one comparison site in the Russifa area. Geochemical analyses reveal a high P₂O₅ content (average 24.32 wt.%), strongly correlating with CaO. There are also significant levels of trace elements, including uranium (0.045 mg/g), cadmium (0.025 mg/g), and zinc (0.099 mg/g). Mineralogical investigation reveals that francolite is the main phosphate mineral. Calcite and quartz are also present. Petrographic analysis reveals the presence of pellets, skeletal fragments, coated grains, and indicators of storm deposits, bioturbation, and fossil-rich layers. These findings indicate that the Al-Tafeh area in northern Jordan is an important yet under-explored area for phosphorite, suggesting that this discovery could have significant economic value. Full article

The purpose of this study is to develop a multiphysical model of agglomeration of low-grade phosphorites with the addition of phosphate-siliceous shales and oil sludge. To achieve these tasks, a numerical approach was used in the COMSOL Multiphysics environment, based on solving the related problems of heat transfer and hydrodynamics during heat treatment of the material. A laboratory vertical tubular furnace made of heat-resistant quartz glass with electric heating was used to study the effect of the temperature field and the velocity of gases on the degree of sintering and the dynamics of phosphorous agglomerate formation under various technological conditions. It has been established that the optimal temperature for the agglomeration process is a layer temperature of 950–1000 °C at a gas flow rate of 1.5–2 m/s, which ensures the formation of durable granules and minimizes sintering heterogeneity. The maximum sintering layer height of the test charge reaches 210–230 mm at pressures of 0.015–0.027 MPa. A comparison of the numerical simulation results with experimental data showed a good agreement, which confirms the practical significance of the proposed model for the design and optimization of industrial processes of agglomeration of phosphorous raw materials. Modern physical and chemical analyses have established the phase, microstructural, and element-by-element characteristics of the studied phosphate-siliceous shale and the product of agglomeration firing. The results of modeling the hydrodynamics of the charge agglomeration process can be recommended to increase the efficiency of processing phosphate-containing waste and reduce energy consumption. Full article

Phosphorite, or phosphate rock, has garnered increasing attention in recent years as a promising unconventional resource for rare earth elements (REEs). This paper presents a processing scheme aimed at recovering both REEs and phosphate values from amine flotation tailings generated during phosphate beneficiation in Florida. In these tailings, REEs are primarily present as monazite and xenotime, often associated with heavy minerals. The proposed flowsheet includes gravity separation to pre-concentrate REE- and phosphate-bearing minerals, followed by flotation to further upgrade both REEs and phosphate, and finally sulfuric acid leaching to extract REEs and phosphate from the flotation concentrate. Gravity separation using a shaking table increased the total REE content from approximately 202 ppm to 657 ppm, with a concentrate yield of 12.51%, REE recovery of around 41%, and P₂O₅ recovery of 33%. Fatty acid flotation of the shaking table concentrate produced a final concentrate containing 1106 ppm REEs and 14.90% P₂O₅, with recoveries of approximately 86% for REEs and 90% for P₂O₅. Subsequent pyrolysis with concentrated sulfuric acid followed by water leaching achieved recoveries of about 85% for REEs and 93% for P₂O₅. While the process demonstrated effective concentration and leaching of REE minerals and apatite, the major challenge to further improving separation and extraction efficiency lies in the fine-grained nature of the valuable minerals and their interlocking with gangue minerals. Full article

In this study, high-energy milled (HEM) samples of natural phosphorites from Estonian deposits were investigated. The activation was performed via planetary mill with Cr-Ni grinders with a diameter of 20 mm. This method is an ecological alternative, since it eliminates the disadvantages of conventional acid methods, namely the release of gaseous and solid technogenic products. The aim of the study is to determine the changes in the structure to follow the solid-state transitions and the isomorphic substitutions in the anionic sub-lattice in the structure of the main mineral apatite in the samples from Estonia, under the influence of HEM activation. It is also interesting to investigate the influence of HEM on structural-phase transformations on the structure of impurity minerals-free calcite/dolomite, pyrite, quartz, as well as to assess their influence on the thermal behavior of the main mineral apatite. The effect of HEM is monitored by using a complex of analytical methods, such as chemical analysis, powder X-ray diffraction (PXRD), wavelength-dispersive X-ray fluorescence (WD-XRF) analysis, and Fourier-transformed infrared (FTIR) analysis. The obtained results prove the correlation in the behavior of the studied samples with regard to their quartz content and bonded or non-bonded carbonate ions. After HEM activation of the raw samples, the following is established: (i) anionic isomorphism with formation of A and A-B type carbonate-apatites and hydroxyl-fluorapatite; (ii) solid-phase synthesis of calcium orthophosphate-CaHPO₄ (monetite) and dicalcium diphosphate-β-Ca₂P₂O₇; (iii) enhanced chemical reactivity by approximately three times by increasing the solubility via HEM activation. The dry milling method used is a suitable approach for solving technological projects to improve the composition and structure of soils, increasing soil fertility by introducing soluble forms of calcium phosphates. It provides a variety of application purposes depending on the composition, impurities, and processing as a soil improver, natural mineral fertilizer, or activator. Full article

The South China Block hosts extensive sedimentary phosphorites that offer valuable insights into both paleoenvironmental reconstruction and rare earth element (REE) resource potential. However, the mechanisms governing REE enrichment in these deposits remain poorly understood. This study investigates two distinct phosphorite layers from the Lower Cambrian Zhujiaqing (ZJQ) Formation in the Bailongtan (BLT) area of the Yangtze Platform using integrated analyses including petrology, XRD, major and trace elements, δ¹³C and δ¹⁸O isotopes, and LA-ICP-MS. The lower thin-bedded phosphorite, composed of finer phosphatic grains (<300 μm), exhibits significantly higher REE concentrations (883.6 ± 160.9 ppm; n = 48) compared to the upper thick-bedded phosphorite (303.2 ± 82.7 ppm; n = 64), which is dominated by larger, reworked grains (300–600 μm). Intervening strata consist of laminated phosphate-bearing carbonates interbedded with quartz, dolomite, and pyrite. PAAS-normalized REE patterns display MREE–HREE enrichment, negative Ce anomalies (avg. 0.60 ± 0.18; n = 18), and positive Y anomalies—indicative of oxic depositional conditions. The elevated REE content in the lower layer, coupled with the lowest δ¹³C values (−4.59‰), suggests enrichment linked to organic matter degradation. A proposed two-stage depositional model links REE enrichment to proximity with REE-rich deep-shelf waters, underscoring the critical role of redox and depositional dynamics in phosphorite-hosted REE accumulation. Full article

The chemical extraction of rare-earth elements (REEs) from Estonian graptolite-argillite (GA) and phosphate rock (Phosphorite, PH) samples has been conducted and analyzed. For the initial leaching process, HCl and HNO₃ with different concentrations were used to extract REEs from GA and PH. Different extraction agents, including ionic liquids, were examined for the extraction of REEs from acidic aqueous solutions in the liquid–liquid extraction step. After leaching and extraction, all samples were characterized using the inductively coupled plasma mass spectrometry method (ICP-MS/MS). The highest REE extraction efficiencies from GA were established with 1-ethyl-3-methyl imidazolium diethyl phosphate (EMImDEPO₄) and from PH using bis(2-ethylhexyl) phosphate (D2EHPA). Full article

The grabbing of phosphorite rocks is an important process in the mining industry. Traditional grabbing technology based on rigid robots faces challenges such as heavy weight, low flexibility, and insufficient safety. This study presents the structural design, characteristic analysis, and modeling of a novel tailored soft robot for phosphorite grabbing (TSRPG). The TSRPG is designed with soft, flexible materials, providing flexible movement and high safety in complex environments. The design inspiration of the robot comes from humans using their thumb and index finger to hold things, and the structural design mainly focuses on the flexibility and grabbing function of the robot. The grabbing function of the TSRPG is exhibited by several actual grabbing experiments. In addition, through characteristic analysis, we explore the robot’s motion properties under various input air pressure conditions. A mathematical model of the TSRPG is developed to depict its characteristics based on the nonlinear ARX model. The developed mathematical model provides a base for promoting the practical application of the TSRPG. Full article

The emergence of soft robots provides new opportunities for developing phosphorite processing equipment. In this article, a soft pneumatic gripper (SPG) for gripping phosphorites is designed. On this basis, the dynamic modeling method and hysteresis inverse compensation control method for the SPG are proposed. First, an SPG for gripping phosphorites is designed based on pneumatic actuation technology. Meanwhile, the gripping ability of the designed SPG is experimentally examined. Next, a dynamic model of the SPG is established by combining the Bouc–Wen model and a linear dynamic model. The output of the established dynamic model can fit the experimental data well, which shows that the established dynamic model of the SPG can describe its motion characteristics. Then, by constructing the inverse expression of the established dynamic model, the hysteresis inverse compensation control method for the SPG is presented to realize its motion control. Finally, the result of the control system simulation illustrates that the presented control method is effective. Full article

Rare earth elements (REEs) are important strategic resources, widely used in various technological fields, especially heavy rare earth elements (HREEs). China has extensive rare earth deposits, with diverse mineral types and a complete range of rare earth elements, characterized by a “heavy south, light north” resource distribution pattern. The rare earth-bearing collophane in the Zhijin area of Guizhou is a typical marine sedimentary phosphorite deposit with large reserves and a high heavy rare earth content. This study investigates the rare earth-bearing collophane in the Zhijin area using X-ray diffraction (XRD), X-ray fluorescence (XRF), and scanning electron microscopy with energy-dispersive spectroscopy (SEM-EDS) to analyze its mineral composition and occurrence characteristics. In terms of flotation, a reverse flotation process for magnesium removal was adopted. By optimizing the flotation parameters, including grinding fineness, collector dosage, pH regulator dosage, and depressant dosage, the optimal flotation conditions were determined. A further mineralogical analysis was conducted on both the flotation concentrate and tailings. The results show that the main minerals in the rare earth-bearing collophane of Zhijin are fluorapatite and dolomite, with dolomite as the primary gangue mineral, and rare earth elements are mainly hosted in fluorapatite. The optimal flotation conditions were achieved when the grinding fineness was −74 μm with an 83% passing rate, XF-1 was used as the collector at a dosage of 300 g/t, sulfuric acid (H₂SO₄) as the pH regulator at 6 kg/t, and phosphoric acid (H₃PO₄) as the depressant at 3 kg/t. By employing an optimal reagent regime and implementing a reverse flotation process consisting of one roughing and one scavenging stage, a phosphate concentrate was obtained with a P₂O₅ grade of 31.61% and an REO content of 0.161%. The P₂O₅ recovery reached 84.22%, while the REO recovery was 78.65%. Compared to the raw ore, the P₂O₅ grade increased by 11.52 percentage points, and the REO content improved by 0.051 percentage points. Mineralogical analysis of the flotation concentrate and tailings revealed that dolomite was effectively removed by reverse flotation, while rare earth elements were successfully enriched in the phosphate concentrate. In conclusion, this study provides an efficient flotation separation process for rare earth-bearing collophane and dolomite, while also offering technical support for the efficient recovery of rare earth resources. This research has significant theoretical and practical implications. Full article

In this study, the authors investigated the briquetting of hydroxyapatite and fluorapatite rock material and evaluated the properties of briquettes prepared in a roller press. This was conducted 10 years after the manufacturing process took place. These rocks are a primary source of the mineral phosphorus, for which demand is high, particularly in agriculture. The proper handling of the material in the industry is required due to its high environmental impact. In order to correctly identify the subject of this study, the authors analyzed its composition using energy-dispersive X-ray spectroscopy, scanning electron microscopy and polarized light microscopy. Afterwards, the authors analyzed the properties of the saddle-shaped briquettes, including their surface roughness (Ra, Rq, Rt), surface Leeb hardness distribution, porosity and density. The briquettes exhibited relatively large Ra values (mean 9.67 µm). The highest hardness was registered at the specimen center (61 HV5), whereas the lowest was at the edge (25 HV5). A high density of 2.51 g/cm³ was achieved in the process. It was possible to obtain saddle-shaped briquettes with reproductible properties, high density (porosity of 21%) and durability without using a binder additive. The study demonstrated that roller press briquetting can be successfully utilized as a method for compacting phosphate-bearing materials for the purpose of storage transportation and further processing. Full article

In the early Cambrian period, a severe greenhouse effect subjected the Gondwanan continents to accelerated erosion, enriching oceanic waters with essential nutrients, including phosphate, silicon, calcium, magnesium, iron, and trace elements. The nutrient flux, sourced from the volcanic composition of west Gondwana, was recorded as sequences of nodular phosphoritic limestones intercalated with chlorite-rich silts, containing ferrous phyllosilicates such as chamosite and chlorite. The abundant and diverse fossil record within these deposits corroborates that the ion supply facilitated robust biogeochemical and nutrient cycling, promoting elevated biological productivity and biodiversity. This paper investigates the early Cambrian nutrient fluxes from the Gondwanan continental region, focusing on the formation of phosphoritic and ferrous facies and the diversity of the fossil record. We estimate and model the biogeochemical cycling within a unique early Cambrian ecosystem located in South Spain, characterized by calcimicrobial reefs interspersed with archaeocyathids that settled atop a tectonically elevated volcano-sedimentary platform. The configuration enclosed a shallow marine lagoon nourished by riverine contributions including ferric and phosphatic complexes. Geochemical analyses revealed varying concentrations of iron (0.14–3.23 wt%), phosphate (0.1–20.0 wt%), and silica (0.27–69.0 wt%) across different facies, with distinct patterns between reef core and lagoonal deposits. Using the Geochemist’s Workbench software and field observations, we estimated that continental andesite weathering rates were approximately 23 times higher than the rates predicted through modeling, delivering, at least, annual fluxes of 0.286 g·cm⁻²·yr⁻¹ for Fe and 0.0146 g·cm⁻²·yr⁻¹ for PO₄³⁻ into the lagoon. The abundant and diverse fossil assemblage, comprising over 20 distinct taxonomic groups dominated by mollusks and small shelly fossils, indicates that this nutrient influx facilitated robust biogeochemical cycling and elevated biological productivity. A carbon budget analysis revealed that while the system produced an estimated 1.49·10¹⁵ g of C over its million-year existence, only about 0.01% was preserved in the rock record. Sulfate-reducing and iron-reducing chemoheterotrophic bacteria played essential roles in organic carbon recycling, with sulfate reduction serving as the dominant degradation pathway, processing approximately 1.55·10¹¹ g of C compared to the 5.94·10⁸ g of C through iron reduction. A stoichiometric analysis based on Redfield ratios suggested significant deviations in the C:P ratios between the different facies and metabolic pathways, ranging from 0.12 to 161.83, reflecting the complex patterns of organic matter preservation and degradation. The formation of phosphorites and ferrous phyllosilicates was primarily controlled by suboxic conditions in the lagoon, where microbial iron reduction destabilized Fe(III)-bearing oxyhydroxide complexes, releasing scavenged phosphate. This analysis of nutrient cycling in the Las Ermitas reef–lagoon system demonstrates how intensified continental weathering and enhanced nutrient fluxes during the early Cambrian created favorable conditions for the development of complex marine ecosystems. The quantified nutrient concentrations, weathering rates, and metabolic patterns established here provide a baseline data for future research addressing the biogeochemical conditions that facilitated the Cambrian explosion and offering new insights into the co-evolution of Earth’s geochemical cycles and early animal communities. Full article

This article examines the process of digesting phosphorites in an acidic solution to create complicated and mixed fertilizers. This study focuses on improving the nutritional content of phosphorus fertilizers by utilizing mineral acids, such as phosphoric, nitric, and sulfuric acids. In particular, the research looks into how phosphate raw materials, such as poor-quality phosphorites from the Central Kyzylkum region, are treated to create fertilizers that are nitrogen-phosphorous (NPh), phosphorpotassium (PhP), and nitrogen-phosphorus-potassium (NPhP). Phosphorites are broken down by nitric acid in the process, yielding calcium nitrate salts and other byproducts that can be treated further. A scanning electron microscope was used in the investigation to examine the fertilizers’ surface microstructure. The findings emphasize how crucial it is to clean and neutralize phosphorus fertilizers in order to enhance product quality and lessen the amount of undesirable salts. The results offer insightful information about enhancing fertilizer output and raising agricultural productivity. Full article

The combined chemical extraction of rare earth elements from acid solutions and electrochemical separation of yttrium by electrodeposition from Estonian phosphorite ore samples containing rare earth elements has been conducted using ionic liquids at room temperature. It is shown that bis(2-ethylhexyl) phosphate can be used to selectively extract yttrium from other low rare earth elements, constituting the basis for further extraction. Electrochemical deposition can then be applied to the concentrated extraction product to separate valuable Y from the more abundant elements, such as Ca, from the natural sample. The addition of Bi salt to the working solution significantly aids REE’s deposition. It is shown that this extraction method can be highly efficient as well as selective when well-controlled different electrodeposition conditions are applied. Full article