Demand For Rare Earth Elements Research Articles

Investigating Physicochemical Methods to Recover Rare-Earth Elements from Appalachian Coals

The demand for rare-earth elements is expected to grow due to their use in critical technologies, including those used for clean energy generation. There is growing interest in developing unconventional rare-earth element resources, such as coal and coal byproducts, to help secure domestic supplies of these elements. Within the U.S., Appalachian Basin coals are particularly enriched in rare-earth elements, but recovery of the elements is often impeded by a resistant aluminosilicate matrix. This study explores the use of calcination and sodium carbonate roasting pre-treatments combined with dilute acid leaching to recover rare-earth elements from Appalachian Basin coals and underclay. The results suggest that rare-earth element recovery after calcination is dependent on the original mineralogy of samples and that light rare-earth minerals may be more easily decomposed than heavy rare-earth minerals. Sodium carbonate roasting can enhance the recovery of both light and heavy rare-earth elements. Maximum recovery in this study, ranging from 70% to 84% of total rare-earth elements, was achieved using a combination of calcination and sodium carbonate roasting, followed by 0.25 M citric acid leaching.

Supercharged fluorescent proteins detect lanthanides via direct antennae signaling

A sustainable operation for harvesting metals in the lanthanide series is needed to meet the rising demand for rare earth elements across diverse global industries. However, existing methods are limited in their capacity for detection and capture at environmentally and industrially relevant lanthanide concentrations. Supercharged fluorescent proteins have solvent-exposed, negatively charged residues that potentially create multiple direct chelation pockets for free lanthanide cations. Here, we demonstrate that negatively supercharged proteins can bind and quantitatively report concentrations of lanthanides via an underutilized lanthanide-to-chromophore pathway of energy transfer. The top-performing sensors detect lanthanides in the micromolar to millimolar range and remain unperturbed by environmentally significant concentrations of competing metals. As a demonstration of the versatility and adaptability of this energy transfer method, we show proximity and signal transmission between the lanthanides and a supramolecular assembly of supercharged proteins, paving the way for the detection of lanthanides via programmable protein oligomers and materials.

Solar driven highly efficient photocatalyst based on Dy2O3 nanorods deposited on reduced graphene oxide nanocomposite for methylene blue dye degradation.

In recent years, the demand for rare earth elements has surged due to their unique characteristics and diverse applications. This investigation focuses on utilizing the rare earth element dysprosium oxide (Dy2O3) for the photocatalytic oxidation of model pollutants under solar light irradiation. A novel RGO-Dy2O3 nanocomposite photocatalyst was developed using a solvothermal approach, Dy2O3 nanorods uniformly deposited onto reduced graphene oxide (RGO) nanosheets. Comprehensive characterization techniques, including Brunner-Emmett-Teller (BET), X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD), Fourier transform-infrared spectroscopy (FTIR), Raman spectroscopy, high resolution - transmittance electron microscopy (HR-TEM), field emission-electron scanning microscopy (FE-SEM), atomic force microscopy (AFM), electron paramagnetic resonance spectroscopy (EPR), photoluminescence spectroscopy (PL), and electrochemical impedance spectroscopy EIS techniques. The UV-visible diffusive reflectance spectroscopy (UV-Vis-DRS) studies revealed a band gap energy of 3.18eV and a specific surface area of 114 m2/g for the fabricated RGO-Dy2O3 nanocomposite. The RGO-Dy2O3 nanocomposite demonstrated a high photocatalytic degradation efficiency of 98.1% at neutral pH for methylene blue (MB) dye for the dye concentration of 10ppm. The remarkable photocatalytic performance was achieved within 60min under solar light irradiation. Reusability tests demonstrated stability, maintaining over 90% photocatalytic efficiency after three cycles. The EPR spectra and quenching experiments confirmed that photogenerated hydroxyl radicals significantly influence the photodegradation processes. The RGO-Dy2O3 nanocomposite photocatalyst, with its green, easy preparation process and recycling capabilities, presents an ideal choice for various applications. It offers a viable alternative for the photocatalytic degradation of organic dyes in real wastewater, contributing to sustainable environmental remediation.

Electrochemical biosensing of cerium with a tyrosine‐functionalized EF‐hand loop peptide

AbstractThe significance of easily detecting rare earth elements (REEs) has increased due to the growing demand for REEs. Addressing this need, we present an innovative electrochemical biosensor, focusing on cerium as a model REE. This biosensor utilizes a modified EF‐hand loop peptide sequence, incorporating cysteine for covalent attachment to a gold working electrode and tyrosine as an electrochemically active amino acid. The sensor was designed such that binding to cerium induces a conformational change in the peptide, affecting tyrosine's proximity to the electrode surface, modulating the current. A calibration curve was generated from cyclic voltammetry current peaks at ~0.55–0.65 V versus a silver pseudo‐reference electrode, with cerium concentrations ranging from 0 to 67 μM in artificial urine. The sensor exhibited a biologically relevant limit of detection of 35 μM and a sensitivity of −0.0024 ± 0.002 (μA μM)−1. These findings offer insights into designing peptide sequences for electrochemical biosensing.

Rare earth elements enrichment and extraction potential of bauxite deposits in Samar, Philippines

Abstract Rare earth elements (REE) play an integral part of modern life, from smartphones to satellites. Dubbed ‘critical metals’, the demand for REE has significantly increased, driven by the growth in global production for green technologies such as e-vehicles, solar panels, wind turbines, and other energy-economic infrastructure. Therefore, there is a need to explore alternative REE sources to ensure continued development of emerging green technologies. A possible alternative REE source is bauxite, which is soil that forms from intense weathering of aluminum oxide-rich rocks exposed to tropical climate. This paper investigates the REE enrichment and extraction potential from bauxite deposits in Paranas, Samar, Philippines. The sampling survey included collection of rock and soil on surface exposures, test pits, and drill cores from accessible portions of the bauxite mineral reservation site. The soil and parent rock samples collected were then subjected to various geochemical and mineralogical analyses. The main ore minerals of aluminum are gibbsite and boehmite; with minor goethite, hematite, and magnetite. Investigation of the geochemical composition of the bauxite reveals a total REE content of up to ~300 ppm, which is one of the highest REE and critical metal content among geological deposits in the country. These results will provide inputs in the design of a green and economical process to recover REE from bauxites. If the bauxite deposits prove to be a valuable REE resource, this study will help maximize the economic potential of the mineral resource in the Philippines and contribute to an economically efficient and environment-friendly way to produce e-tech elements for the country.

Recycling impacts of renewable energy generation-related rare earth resources: A SWOT-based strategical analysis

As the global energy mix transforms and renewable energy technologies rapidly develop, there has been a significant increase in the demand for rare earth elements, which play a crucial role in renewable energy systems. By recycling rare earth resources from obsolete equipment, the reliance on newly mined rare earth resources can be reduced, thereby reducing the related environmental and energy footprints and increasing the stability of the supply chain. This study aims to systematically and strategically analyze and discuss the recycling impacts of renewable energy generation (REG)-related rare earth resources in terms of environmental, economic, social, and governance aspects. A SWOT strategical analysis framework integrating a management cycle and intelligent text data mining is built to address the above tasks from an ESG (Environment, Society, and Governance) perspective. The SWOT analysis of the rare earth recycling impacts focuses on strengths (e.g., reduced dependence on rare resources, reduced environmental and emission pressure), weaknesses (e.g., high cost, technology and management complexity), opportunities (e.g., policy support, technological innovations, diversification of the global supply chain), and threats (e.g., market volatility, the emergence of alternative materials). This analysis framework reveals textual topic changes and suggests cyclic and strategical improvement pathways to analyze the multi-dimensional recycling impacts. The text data analysis results indicate that the trend of rare earth recycling is gradually transformed from technologies, supply and demand, and secondary resources into resource and environment sustainable development. Beyond overcoming identified challenges, future pathways should focus more on the integration of advanced emerging technologies, life cycle management, and dynamic adjustment of recycling strategies. This study could provide policymakers and industry practitioners with recommendations and outlook on current development status and improvement strategies to promote REG-related rare earth recycling.

Simulation and Economical Analysis of Hydro-Nd Process for the Recovery of Rare Earth from End-of-Life Permanent Magnets: NEW-RE and INSPIREE projects

The growing demand for rare earth elements (REEs) and sustainable development issues have made the REEs recovery from permanent magnets (PMs) attract the attention of many researchers in the last decade. The NEW-RE and INSPIREE projects have been introduced to evaluate the recovery of REE elements from permanent magnets on a pilot and industrial scale. In this research, the economic aspect of the mentioned projects was performed using SuperPro software. The main aim of the work is to highlight the critical aspects of the process for a targeted optimization. The results showed that the CAPEX and OPEX for treating 3,600 tons/year of permanent magnets are 9 and 110 million euros, respectively, and an EBITDA of 4.8 million euros can be achieved (payback period less than two years). In the economic model, the cost of spent PMs was considered equal to 50% of its REEs value (14,251 €/ton). Also, it was found that the main OPEX costs are raw materials (65%) and energy (16%), respectively. It needs to be pointed out that the maximum price of permanent magnets can be 15,230 €/ton (BEP).

Rare Earth Elements: A Global Scenario and Understanding of Their Impacts, Challenges, and Recycling Processes in Bangladesh through Global Literature

Over the last decade, rare earth elements (REEs) have gained international attention due to their multiple usages. Because of their unique properties, the elements play a vital role in electronics, defense, aerospace, transportation, agriculture, and communications technology. They are also critical to the high technology and low carbon economy. These applications drive demand for rare earth products and promote the steady development of the rare earth industry. In this paper, we have reviewed the current scenario, applications, challenges, and impacts of REEs from a global perspective. It is seen that China leads in the production of REEs worldwide. Globally, REE production is associated with a range of environmental issues, including mining-related pollution, the generation of radioactive waste, water scarcity, soil contamination, and deforestation, all of which impact both humans and animals. Drawing from global literature, we discussed a comparative scenario of REEs in Bangladesh. In Bangladesh, the rising population has led to increased REE demand, and we utilized secondary sources to deduce REE impacts. We overviewed aspects such as 100% electricity coverage, import opportunities from the other countries, and government initiatives, all contributing to the growing REE demand and e-waste generation in Bangladesh. Currently, there is no recycling process available. Subsequently, we highlighted the situation in Bangladesh regarding REE management, presented suggestions for recycling based on recent global literature, and provided recommendations for the future.

Chloridizing roasting studies of spent NdFeB magnets for recovery of rare earth values

The increased demand for rare earth elements in advanced technological applications and supply shortages call for metal recovery from secondary sources. Permanent magnet (Nd2Fe14B or NdFeB) may serve as a potential secondary source due to its high rare earth (Nd+Pr+Dy: ∼30 %) content and its vast application. The present study utilizes a chloridizing roasting (CaCl2.2 H2O) pre-treatment process followed by water leaching, acid leaching (0.5 M HCl, S/L =1/10 g/ml, 90 °C, 3 h), oxalic acid precipitation and calcination (850 °C, 2 h) to obtain mixed rare earth oxides. The process was optimized based on temperature (400–700 °C), dosage (CaCl2.2H2O: NdFeB=0.5:1–2.5:1), and time (30–120 min) on the rare earth dissolution. The theoretical activation energy for the chloridizing roasting process is estimated as 22.3 (OFW) and 16.7 kJ/mol (KAS), while the experimental activation energy for Nd and Dy dissolution was determined to ∼29.3 and ∼17.7 kJ/mol, respectively depicting product layer diffusion-controlled kinetics. Higher dosages of CaCl2.2H2O (1.5:1 and 2:1) favored NdOCl formation, thereby, higher dissolution; however, further higher dosage (2.5:1) leads to reduced Nd dissolution due to higher CaO formation and acid consumption by Ca during leaching. Incomplete oxidation at lower temperatures (400 °C) and iron dissolution impair the Nd dissolution and selectivity. Excessive oxidation at >700 °C favors the formation of NdFeO3, decreasing Nd dissolution. The maximum dissolution of Nd was ∼89 %, while for Dy, it was ∼88 % at optimum conditions of 600 °C, 90 min, 2:1. Water leaching post-roasting leads to ∼87 % Ca removal and the precipitation efficiency of rare earth oxalates was 99 %. The overall extraction for rare earth elements was ∼89 %, and 1 kg of NdFeB powder can yield ∼285 g of rare earth oxides (∼239 g Nd2O3, ∼14 g Dy2O3) with 96 % purity. Further, this study demonstrates that using CaCl2.2 H2O as a solid chlorinating agent in chlorination roasting enhances recovery rates of mixed rare earth oxides while providing a safer and more environment-friendly alternative for industrial applications.

Polymer-Based Extracting Materials in the Green Recycling of Rare Earth Elements: A Review.

Rare earth elements (REEs) are becoming increasingly important in the development of modern and green energy technologies with the demand for REEs predicted to grow in the foreseeable future. The importance of REEs lies in their unique physiochemical properties, which cannot be reproduced using other elements. REEs are sourced through mining, with global exploration of additional commercially viable mining sites still ongoing. However, there is a growing need for recycling of REEs due to the current supply of REEs not matching the growing demand, the environmental impact of REE mining and processing (the so-called "balance problem"), and the generation of large volumes of harmful electronic waste (e-waste). Industrial REE processing is mainly carried out by hydrometallurgy processes, particularly solvent extraction (SX) and ion exchange (IX) technologies. However, these methods have a significant environmental impact due to their intensive use of harmful and nonsustainable reagents. This Review highlights the development of approaches involving polymer-based extracting materials for REE manufacturing as more sustainable alternatives to current industrial REE processing methods. These materials include supported liquid membranes (SLMs), solvent impregnated resins (SIRs), macro and micro capsules, polymer inclusion membranes (PIMs), and micro polymer inclusion beads (μPIBs). Polymer-based extracting materials have the advantage of more economical regent usage while applying the same extractants used in commercial SX, enabling applications analogous to the current industrial process. These materials can be fabricated by a variety of methods in a diverse range of physical formats, with the advantages and disadvantages of each material type described and discussed in this Review along with their applications to REE processing, including e-waste recycling and mineral processing.

Carbonatites and related mineralization: an overview

Despite of their scarcity, carbonatites are documented from diverse geological settings, including cratons, continental rifts, orogenic belts and large igneous provinces, which range in age from the Archean to Recent. This study provides a concise overview of the evolution of igneous carbonatites, compiling data on their diverse characteristics and classifying them into mantle- and crustal-derived subtypes. Mantle-derived carbonatites, typically associated with alkaline rocks, are enriched in rare earth elements (REEs) and display geochemical affinities to the mantle. By contrast, crustal-derived carbonatites usually show much lower REE contents and crustal-affinity geochemical features similar to sedimentary carbonaceous rocks. Our study documents the significant economic potential of carbonatites that can host world-class deposits of REE, rare metals, alkaline earth metals and non-metallic resources. Typically, the key processes controlling REE mineralization include the low-degree melting of refertilized mantle, liquid immiscibility, fractional crystallization and hydrothermal fluids. Thus, carbonatites are of significant economic value due to the rapidly increasing global demand for REEs, mainly driven by the ‘green energy transition’.

Identifying Rare Earth Elements Using a Tripod and Drone-Mounted Hyperspectral Camera: A Case Study of the Mountain Pass Birthday Stock and Sulphide Queen Mine Pit, California

As the 21st century advances, the demand for rare earth elements (REEs) is rising, necessitating more robust exploration methods. Our research group is using hyperspectral remote sensing as a tool for mapping REEs. Unique spectral features of bastnaesite mineral, has proven effective for detection of REE with both spaceborne and airborne data. In our study, we collected hyperspectral data using a Senop hyperspectral camera in field and a SPECIM hyperspectral camera in the laboratory settings. Data gathered from California’s Mountain Pass district revealed bastnaesite-rich zones and provided detailed insights into bastnaesite distribution within rocks. Further analysis identified specific bastnaesite-rich rock grains. Our results indicated higher concentrations of bastnaesite in carbonatite rocks compared to alkaline igneous rocks. Additionally, rocks from the Sulphide Queen mine showed richer bastnaesite concentrations than those from the Birthday shonkinite stock. Results were validated with thin-section studies and geochemical data, confirming the reliability across different hyperspectral data modalities. This study demonstrates the potential of drone-based hyperspectral technology in augmenting conventional mineral mapping methods and aiding the mining industry in making informed decisions about mining REEs efficiently and effectively.

Potential for high-grade recovery of rare earth elements and cobalt from acid mine drainage via adsorption to precipitated manganese (IV) oxides

High demand for rare earth elements (REEs) has increased interest in their recovery from unconventional sources, such as acid mine drainage (AMD). AMD contains elevated concentrations of Mn, Fe, and Al, which precipitate as (oxy)hydroxide minerals as pH is raised. These precipitates can remove cations including REEs and Co from solution via sorption and/or coprecipitation. In this study we developed a method to recover these critical minerals by sorption to MnO2, precipitated by oxidation of in situ Mn (II) with added KMnO4 at acidic pH. MnO2 solids were prepared with varying concentrations of KMnO4, SO42−, and Cl−, to elucidate the effects of excess KMnO4, SO42− concentration, and ionic strength on adsorption. When using a stoichiometric ratio of Mn (II) and KMnO4, 100% removal of REEs and Co occurred at approximately pH 3.5, nearly 2 pH units lower than was observed by sorption to Fe and Al hydroxysulfates. When using excess KMnO4 nearly 100% removal of REEs and Co was accomplished at approximately pH 2, although SO42− was found to inhibit REE sorption. From these results, we developed a two-stage process for recovery of REEs from AMD; a preliminary pH adjustment to remove Fe and Al hydroxy-sulfates, followed by adding KMnO4, precipitating MnO2, enabling recovery of REEs and Co. We tested this process in a representative synthetic AMD, achieving a grade of 6.16 mg REEs per g of solid, which is 65 % of the maximum possible grade based on solution composition. Fractionation of REEs was observed, with light REEs (LREEs) preferentially sorbed to MnO2 relative to both medium REEs (MREEs) and heavy REEs (HREEs). In contrast, preferential sorption of HREEs was observed for sorption to Fe and Al oxyhydroxides at all pH ranges. These results suggest the mechanisms of REE sorption differ among the solids and warrant further study.

Acute and chronic toxicity of rare earth elements-enriched sediments from a prospective mining area: Effects on life history traits, behavioural and physiological responses of Gammarus fossarum (Crustacea Amphipoda)

Rare earth elements (REE) have an essential role and growing importance in the world's economy. They are attracting interest from society, policymakers, and scientists. The rapidly growing global demand for REE in several strategic industrial and agricultural sectors led many countries to consider the (re)-opening of mining activities for REE extraction. Hence, their increasing use led to the disruption of their biogeochemical cycles with anthropic abnormalities already observed in aquatic ecosystems. Nonetheless, REE remain less studied, and their mechanisms of toxicity actions are not fully understood. As amphipods, Gammarus fossarum represent an important part of the aquatic macroinvertebrate assemblage and are generally used in ecotoxicological studies for their high ecological relevance. However, their use for the study of REE effects has been rather limited so far. The current study aims to assess the potential effects of two naturally REE-enriched sediments (N2 and B4) on G. fossarum. Effects on life history traits, behavioural and physiological responses have been evaluated. Exposing G. fossarum males for 72h to sediments N2 and B4 led to a decrease in haemolymph osmolality and locomotion while an increase in ventilatory activity was observed. Exposing G. fossarum pre-copula pairs with females at the same reproductive stage to the naturally REE-enriched sediments, for one moult cycle duration (∼30 days) showed that sediment B4 led to i) a significant uptake of REE, ii) a significant decrease in the proportion of females with oocytes and iii) a significant reduction in the total number of juveniles. The physicochemical analyses of sediments showed that B4 contains the highest amount of REE with a higher proportion of light REE. The present study gives the first insights into the potential toxicity of REE on G. fossarum as they may have deleterious effects on G. fossarum population's dynamics, which may alter the functioning of aquatic ecosystems.

Tailoring the Use of 8-Hydroxyquinolines for the Facile Separation of Iron, Dysprosium and Neodymium.

Permanent magnets (PMs) containing rare earth elements (REEs) can generate energy in a sustainable manner. With an anticipated tenfold increase in REEs demand by 2050, one of the crucial strategies to meet the demand is developing of efficient recycling methods. NdFeB PMs are the most widely employed, however, the similar chemical properties of Nd (20-30 % wt.) and Dy (0-10 % wt.) make their recycling challenging, but possible using appropriate ligands. In this work, we investigated commercially available 8-hydroxyquinolines (HQs) as potential Fe/Nd/Dy complexing agents enabling metal separation by selective precipitation playing on specific structure/property (solubility) relationship. Specifically, test ethanolic solutions of nitrate salts, prepared to mimic the main components of a PM leachate, were treated with functionalized HQs. We demonstrated that Fe3+ can be separated as insoluble [Fe(QCl,I)3] from soluble [REE(QCl,I)4]- complexes (QCl,I -: 5-Cl-7-I-8-hydoxyquinolinate). Following that, QCl - (5-Cl-8-hydroxyquinolinate) formed insoluble [Nd3(QCl)9] and soluble (Bu4N)[Dy(QCl)4]. The process ultimately gave a solution phase containing Dy with only traces of Nd. In a preliminary attempt to assess the potentiality of a low environmental impact process, REEs were recovered as oxalates, while the ligands as well as Bu4N+ ions, were regenerated and internally reused, thus contributing to the sustainability of a possible metal recovery process.

Preventing emulsification during rare earths solvent extraction by the addition of Span 80 to enhance the interfacial stability of the P507 oil droplets

The demand for rare earth elements is increasing daily with rapid economic development, thereby increasing the requirements for its separation and purification technologies. The major method for purification and separation of rare earth elements in the industry is currently solvent extraction. In the actual production process, emulsification often occurs because of improper control of the organic phase, aqueous phase properties or operating conditions, and resulting in resource wastage and environmental pollution. This has become an issue that restricts the development of the rare earths industry. To prevent emulsification during rare earths solvent extraction, the organic structure of the P507-kerosene solution was regulated by the addition of Span 80 as a regulator. This study investigated the effects of Span 80 content, P507 concentration, saponification degree and the amount of pre-loading rare earth elements in the organic phase after adding Span 80 on the extraction efficiency of Er3+ and oil content in the raffinates. The results demonstrated that when the content of Span 80 was 6 %, the saponification degree of P507 in the organic phase was 10 %, the concentration of Er3+ in the aqueous phase was 0.5 g /L, the pH value in the aqueous phase was 3, the phase ratio (VO: VA) was 1:2, the extraction efficiency could still reach more than 99 %, and the oil content in the raffinates was 13.9 mg/L. The results demonstrated that the final extraction efficiency did not decrease; however, the extraction rate of rare earth elements did. Further, the oil content in the raffinates decreased greatly after the addition of Span 80. The mechanism was investigated using Fourier-transform infrared (FTIR) spectroscopy and atomic force microscopy (AFM). The interfacial stability of P507 oil droplets was enhanced by the addition of Span 80. Emulsification was, thus, effectively prevented and the dissolution loss of the organic phase was greatly reduced. The results provide a novel method for preventing emulsification during rare earths extraction at the source, and a novel idea for preventing resource loss and protecting the ecological environment.

Sodium alginate/polyvinyl alcohol for the recovery of rare earth elements from mining wastewater: Mechanism and properties

With the demand for rare earth elements (REEs) increasing in the high-tech sector, the recovery of REEs from secondary sources is becoming very critical. In this study, sodium alginate/polyvinyl alcohol (SA/PVA) beads obtained by cross-linking alginate with polyvinyl alcohol were used to recover REEs from real rare-earth wastewaters. The results showed that SA/PVA beads are less affected by temperature and exhibited adsorption selectivity for REEs. The efficiency of adsorbing REEs ranged from 27.6% to 52.6%, but was significantly higher than that of 9.2% Mn. Meanwhile, among the observed REEs, SA/PVA beads revealed a preference for light REEs (44.3% − 52.6%). The adsorption process was investigated utilizing advanced characterization methods, namely Scanning Electron Microscope, Fourier Transform Infrared Spectrometer, and X-ray Diffraction Spectra. Combined with the results of Pearson correlation analysis, we proposed that the adsorption process involves the combined effects of ion exchange, complexation, electrostatic interaction and pore filling. As well, a desorption efficiency of more than 76.9% can be achieved with sodium citrate, which makes possible the effective recovery of REEs. In summary, this study provides a promising green, environmentally friendly and sustainable material for the enrichment and recovery of REEs from mining wastewater.

Removal and Recovery of Europium with a New Functionalized Mesoporous Silica-Based Adsorbent

The discharge of acid mine drainage (AMD), characterized by a high concentration of rare earth elements (REEs), poses a significant threat to the health of ecosystems surrounding water sources. The global market demand for REEs has experienced a notable surge in the past decade. Consequently, recovering REEs from waste streams like AMD not only benefits the environment but also offers financial advantages. Europium (Eu), the rarest among REEs, constitutes only 0.1% w/w in monazite and bastnaesite ores. Eu is extensively used in the production of phosphors, alloys, and additives, and is a critical raw material for developing smart devices, ranging from high-resolution color screens to circuitry. Traditional adsorbents typically exhibit limited selectivity towards REE recovery. Mesoporous silica materials, such as SBA15 (Santa Barbara Amorphous-15), provide excellent tunability and modification capabilities, making them an attractive and cost-effective alternative. This research focused on two key aspects: (i) evaluating the dynamic adsorption column performance of granulated SBA15–NH–PMIDA to preferentially recover Eu, and (ii) employing mathematical modeling to optimize the dynamic adsorption column’s operating conditions for real-world applications with a minimal number of experimental runs. Granulated SBA15–NH–PMIDA was chosen as the adsorbent due to its high adsorptive capacity and selectivity in capturing Eu. The study revealed that granulated SBA15–NH–PMIDA exhibited 57.47 mg/g adsorption capacity and an 81% selectivity towards Eu. Furthermore, SBA15–NH–PMIDA demonstrated preferential adsorption toward Eu in complex multi-component solutions, such as AMD. The linear driven force approximation model (LDFAM) provided an acceptable simulation (R2 > 0.91) under varying operational conditions. This validates the use of the model as a tool to effectively simulate and optimize column experiments that used granulated SBA15–NH–PMIDA to recover Eu.

Highly selective recovery of rare earth elements from mining wastewater using phyto-synthesized biochar dispersed iron nanoparticles

Recovery of rare earth elements (REEs) from secondary sources such as mining wastewater has attracted much recent attention due to the rising global demand for REEs and the need to environmentally protect potentially contaminated mine sites. One significant issue it that most adsorbents proposed for removal and/or recovery of REEs are not generally selective for REEs. In this study, biochar dispersed iron nanoparticles synthesized using a plant extract (BC-FeNPs) were successfully used for the selective recovery of REEs from mining wastewater, where the Kd values were Nd(III) (918 mL∙g−1), Eu(III) (1253 mL∙g−1), Tb(III) (1119 mL∙g−1), Dy(III) (1032 mL∙g−1), Lu(III) (1898 mL∙g−1), compared to only 23.9 mL∙g−1 for Zn(II). The maximum adsorption efficiency of REEs for the composite was higher than the constituent parts being 88.4 % for BC-FeNPs, but only 8.72 % for biochar and 82.4 % for FeNPs, respectively. FTIR, XPS and Zeta potential analysis suggested that the observed selective adsorption of REEs, involved interactions of REEs with O and N, as well as ion-exchange with H+ from the biochar and capping layer, as well as electrostatic interactions. The desorption efficiency of bound REEs from BC-FeNPs was > 85 % when using acetic acid, and was attributed to efficient competitive ion exchange. Pearson correlation analysis further demonstrated that the adsorption mechanism included ion complexation, ion exchange and electrostatic adsorption, while the desorption mechanism was mainly via ion exchange. Overall, BC-FeNPs has significant potential to practically recover REEs from mining wastewater having demonstrated excellent reusability after five adsorption–desorption cycles.

Green and Sustainable Rare Earth Element Recycling and Reuse from End-of-Life Permanent Magnets

Rare earth elements (REEs) are key materials for the development of renewable energy devices such as high-power magnets for wind turbines, electric vehicles, or fuel cells for hydrogen generation, aiming to fulfill the objectives of the European Green Deal for a carbon-neutral economy. The increased demand for REEs and their criticality strongly require the improvement of their extraction technologies from primary resources and the enhancement of their circularity reuse rate from secondary resources. The aim of this paper is to focus attention on the possibilities offered by emerging methods such as microwave (MW) treatment and mechanochemistry in waste electric and electronic equipment (WEEE) processing and the reuse of end-of-life (EoL) magnets, directed toward the tailoring of rational REE material flows. The discussed investigation examples explore some key features of conventional and new methods for efficient, environmentally friendly, and scalable REE extraction and reuse, with the final goal of producing recycled NdFeB powders, with potential use in the redesign and fabrication of new REE-based magnets.