Search Results (506)

The increasing use of electric vehicles has led to a growing demand for rare-earth elements, particularly neodymium (Nd), which is a critical component of Nd–Fe–B permanent magnets used in traction motors. End-of-life electric vehicle motors are therefore considered promising secondary resources for Nd recovery. In this study, a pyrometallurgical process using non-ferrous smelting slag as a flux was proposed for recovering Nd from Nd–Fe–B magnets contained in waste electric vehicle motors. Steel and magnet fractions obtained from a dismantled motor were melted at approximately 1600 °C under an air atmosphere, and Fe₂O₃ was added as an oxidizing agent to promote the selective oxidation of Nd. The oxidized Nd was subsequently partitioned into the slag phase as Nd₂O₃ through metal–slag separation. The effects of the slag flux addition ratio, Fe₂O₃ content, slag flux type, and crucible material on Nd recovery behavior were systematically investigated. Increasing the fayalite-based slag flux addition enhanced Nd transfer into the slag phase, and the highest Nd recovery of approximately 80% was obtained at a slag flux addition ratio of 30 wt%. The addition of 2 wt% Fe₂O₃ was found to be suitable for promoting stable Nd oxidation and efficient slag–metal separation. The non-ferrous smelting slag exhibited chemical and phase characteristics comparable to those of synthetic fayalite slag flux, resulting in similar Nd recovery performance. In addition, the crucible material significantly affected the process stability and Nd recovery behavior. Although a carbon crucible showed relatively high Nd recovery, severe slag foaming and crucible erosion occurred during melting. In contrast, alumina and MgO crucibles provided stable process conditions with comparable Nd recovery behavior, whereas zirconia crucibles caused relatively higher Nd loss. These results demonstrate that non-ferrous smelting slag can be effectively used as a flux for the pyrometallurgical recovery of Nd from end-of-life electric vehicle motors, offering a potential route for sustainable rare-earth recycling. Full article

Rare earth elements (REEs) are increasingly recognized as modulators of male reproductive health. This review presents the first comprehensive and critical analysis of the detrimental and potentially beneficial effects of REEs on male vertebrate reproductive function. In vivo and in vitro studies show that elements, particularly Gadolinium, Lanthanum, and Yttrium, share a toxicological profile characterized by oxidative stress, inflammation, mitochondrial dysfunction, endocrine disruption, and impairment of the blood–testis barrier. These mechanisms converge on both somatic and germ cell populations, ultimately compromising spermatogenesis and hormonal balance. Limited epidemiological data in humans are consistent with experimental findings, indicating inverse associations between seminal REE levels and sperm quality. CeO₂ nanoparticles represent an exception, showing dose-dependent duality: although some murine studies describe toxic effects, a broader and more consistent body of evidence indicates their protective action by restoring testicular homeostasis in diabetic models, in rats exposed to pesticides, pharmacological agents or irradiation, and in in vitro-treated spermatozoa. Preliminary data on Yttrium (YO) and Gadolinium (GdVO₄) nanoparticles similarly point to protective effects under pathological conditions, whereas Neodymium and Samarium show reproductive toxicity, including hormonal disruption and impaired sperm quality. Overall, REEs cannot be considered a homogeneous class: some pose reproductive hazards, others show potential biomedical utility. A systematic, mechanistic research framework is needed to resolve these dualities. It should contextualise reproductive risks in relation to the growing environmental and occupational exposure to REEs, while simultaneously exploring the biomedical potential of those elements that exhibit protective profiles. Full article

Rare earths are a strategically vital mineral resource on a global scale; the security of their supply chain and their recycling face severe challenges amid dual pressures of resource scarcity and environmental protection. This study focuses on the reverse supply chain for rare earth permanent magnet materials—specifically those based on praseodymium and neodymium—constructing a two-level game model comprising a rare earth oligopoly (Stackelberg leader) and two recyclers (Cournot followers). It systematically analyzes the dual decision-making behavior of recyclers between “recycling and selling” and “in-house remanufacturing”, and examines the impact of two policy instruments—government subsidies and environmental taxes—on the supply chain equilibrium. The study employs reverse induction to solve the game equilibrium and combines this with numerical simulation methods to compare the differing effects of the two policies on key indicators such as product output, market share, profit distribution, waste recovery volume, and recycling rates. The results indicate that there is strategic coordination and resource competition in recyclers’ decisions regarding recycling and remanufacturing, causing them to assume dual roles as both “suppliers” and “competitors” within the supply chain. Subsidy policies significantly incentivize recycling and remanufacturing activities, thereby increasing the recycling rate, but exert a slight squeeze on the profits of rare earth conglomerates. Environmental tax policies effectively curb primary mining and promote resource circulation, but may have a negative impact on the remanufacturing industry. Currently, value within the closed-loop rare earth supply chain is highly concentrated among upstream oligopolistic enterprises, whilst the recycling segment suffers from insufficient economic incentives and significant policy dependency. This study provides theoretical support and decision-making references for the government to optimize policy combinations and promote the high-quality development of the rare earth recycling industry. Full article

NdFeB waste is an important rare earth secondary resource, and the current industrial practice primarily employs a hydrochloric acid preferential dissolution method to recover rare earth elements (REEs). However, approximately 1% of REEs (e.g., cerium oxide, neodymium oxide, praseodymium oxide, and dysprosium oxide) remain in the leaching residue, resulting in low recovery efficiency. This work puts forward mechanochemical leaching (integrating mechanical activation and acid leaching) to replace traditional agitated leaching, which realizes synchronous mechanical activation and acid leaching within a stirred ball mill. A systematic comparison is conducted between these two leaching technologies, and the influences of operational variables on rare earth leaching efficiency are explored. The experimental results reveal that sustained mechanical grinding can pulverize particles down to the submicron level, induce substantial lattice distortion and amorphous transformation, destroy the physical coating of rare earth-bearing phases by iron oxides, and thereby drastically improve the extraction efficiency of REEs. The optimal conditions were determined as follows: stirring speed of 700 r/min, leaching temperature of 85 °C, HCl concentration of 1 mol/L, leaching time of 180 min and solid–liquid ratio of 100 g/L. Furthermore, this study reveals the synchronous evolution mechanism of particle refinement and phase transformation during mechanochemical leaching, providing an alternative and more economical recycling route for NdFeB waste. Full article

Techniques such as adsorption have been widely adopted to remove residual microplastics (MPs) because they are efficient at removing contaminants from aqueous environments. In this study, we report a novel, low-cost, biodegradable, and scalable biocomposite (LCMAG NaOH) derived from Luffa cylindrica fruit (LC) and micrometric natural magnetite (MAG), prepared without organic solvents, for the removal of MPs. The performance of LCMAG NaOH was evaluated for the removal of polystyrene (PS) and polyethylene terephthalate (PET) MPs, with particle sizes ranging from 75 to 600 µm in three distinct aqueous media: drinking water, simulated seawater, and water collected from the eutrophic lake of Dourados, MS, Brazil. The material was also evaluated for capture capacity and for reutilization in drinking water over three cycles, using a neodymium magnet. The biocomposite exhibited maximum removal capacities of 163 mg g⁻¹ and 158 mg g⁻¹ for PS and PET, respectively, in drinking water. Additionally, it demonstrated high magnetic recovery efficiency (>90% of the initial mass) and good reusability after immersion (10 and 20 min) and a dry step during the first cycle. Full article

Given the scarce data in the literature regarding the lanthanide content of Greek monofloral honey, Sc (Scandium), Y (Yttrium), La (Lanthanum), Ce (Cerium), Pr (Praseodymium), Nd (Neodymium), Sm (Samarium), Eu (Europium), Gd (Gadolinium), Tb (Terbium), Dy (Dysprosium), Ho (Holmium), Er (Erbium), Tm (Thulium), Yb (Ytterbium), Lu (Lutetium) and Th (Thorium) were determined in honeydew and nectar honey, using inductively coupled plasma mass spectrometry (ICP-MS). Results showed that, in general, honeydew honey had a higher lanthanide content than nectar honey, even though the determined values were below the limit of quantification. Preliminary reference values in this case for pine honey were Ce (26.82 ± 21.49 ng/L) and La (15.25 ± 11.82 ng/L). Adulteration testing was also performed using elemental analysis coupled to isotope ratio mass spectrometry (EA-IRMS), where no adulteration with cheap sugars was detected. Factor analysis identified the principal lanthanides related to honey botanical origin, basically Ce, and the k-NN algorithm classified the samples, achieving a training classification rate of 81.8% and a hold-out classification rate of 76.5%. Even in low amounts, lanthanides may contribute to the botanical origin identification of monofloral honey. Full article

Neodymium (Nd) and dysprosium (Dy) are two critical rare earth elements for fabricating NdFeB permanent magnets, which have crucial applications in modern technologies. The increasing global demand for Nd and Dy emphasizes new efficient processes for their recovery and purification, which are technologically challenging due to their close physical and chemical properties. Through systematic exploration, it was found that Lewatit VP OC 1026 resin impregnated with di-(2-ethylhexyl) phosphoric acid (D2EHPA) had a strong adsorption preference for Dy³⁺ over Nd³⁺, which is highly suitable for Dy-Nd separation from their mixed solutions under optimized conditions. The loaded resin could be eluted using dilute sulfuric solutions for recycling to the adsorption process. By employing a multistage adsorption-elution process analogous to distillation, efficient Dy-Nd separation and purification were realized from their mixed solution, with a prospective purity of 99.13% and recovery of 97.45% for Dy and a prospective purity over 99.96% and recovery of above 99.90% for Nd, despite the large concentration disparity between Dy and Nd, where Nd concentration is over 26 times that of Dy. This research demonstrates that efficient recovery and purification of metals from aqueous solutions can be achieved using selective resin adsorption processes analogous to distillation, despite large concentration differences of the metals in the solutions, which presents new alternative approaches. Full article

Green-synthesized Nd-doped (2%)-ZnO samples were produced using hydrothermal synthesis (HT) and freeze-drying (FT) procedures. A water extract from Vaccinium vitis-idaea leaves was used to modify the Nd-containing zinc acetate solution. The hydrothermal synthesis was carried out in an autoclave at 170 °C for 8 h. The lyophilization process was carried out for 20 h at 0.15 mbar and then for a further 4 h at 0.10 mbar and at a temperature of −100 °C. The final treatment after both these procedures was carried out at 400 °C for 2 h. Both synthesis methods produced mixtures of rugby-like and ridged ZnO particles. The FT particles possess smaller crystallites sizes (24 nm) and higher polarity (I002/I100) in comparison with the hydrothermally obtained particles. It was ascertained by EPR analyses that there was a higher concentration of oxygen-vacancies-related paramagnetic centers after freeze-drying synthesis (more intensive line at g = 2.000). The photocatalytic reaction rates of the freeze-dried samples toward Malachite Green dye discoloration were found to be higher than those of the HT samples. These rates were greatly affected by the smaller crystallites sizes, higher number of singly ionized oxygen vacancies in the crystal lattice and higher surface polarity. Full article

An improved method for separating magnetic minerals based on an isodynamic magnetic field is proposed in this work. The magnetic field distribution generated by the system was first analyzed through numerical simulations performed with finite element electromagnetic simulation software, and the simulation accuracy was subsequently validated against experimental data. Through system modeling and parameter sensitivity analysis, the regulatory mechanisms of various parameters of the field properties were thoroughly investigated. Numerical results show that a constant magnetic force field forms in the separation zone at a 25° arc center angle of the curved pole head, while poor field uniformity occurs at 20° or 30°. A stable constant magnetic force field can be generated in the separation zone when the large arc radius of the curved pole head is 300 mm, 600 mm or 1200 mm, or when permanent magnet materials including N30–N45-grade neodymium iron boron (NdFeB) and ferrite are adopted. The large arc radius of the curved pole head, as well as the type and grade of the permanent magnet, only affect the magnitude of the magnetic force in the separation zone, with no significant correlation with the uniformity of the constant magnetic force field. A constant magnetic force field is generated when the thickness of the side patch magnet on the curved pole head is 40–70 mm and the magnetic system working air gap is 50–60 mm; the magnetic force field will lose uniformity once the parameters deviate from the above ranges. Full article

This study investigates the sorption, structural, and morphological properties of an interpolymer system (IPS) based on Amberlite IR120 (H⁺) and KU-2-8 (H⁺) cation exchangers with acidic sulfonic groups (−SO₃H), applied for the selective sorption of dysprosium (Dy³⁺), neodymium (Nd³⁺), and samarium (Sm³⁺) ions from aqueous solutions. The sorption activity was evaluated for seven systems with molar ratios ranging from 6:0 to 0:6 over a contact time of up to 48 h within a pH range of 2.0 to 5.0. The interpolymer pair with a molar ratio of 5:1 demonstrated the highest sorption efficiency at pH 5.0, yielding extraction degrees of 61.8% for Dy³⁺, 62.0% for Nd³⁺, and 64.4% for Sm³⁺. Equilibrium data were accurately described by the Langmuir isotherm model (R² > 0.974), indicating a dominant monolayer chemisorption mechanism. The maximum monolayer adsorption capacities (q_m) followed the order Dy(III) (189.59 ± 31.52 mg/g) > Sm(III) (162.27 ± 52.38 mg/g) > Nd(III) (139.90 ± 35.40 mg/g). The selectivity toward dysprosium was supported by distribution coefficients (Kd) and separation coefficients (β_Dy/Nd = 1.557 and β_Dy/Sm = 1.757 for the 6:0 system). FTIR analysis confirmed the direct coordination of lanthanide ions by sulfonic groups, as evidenced by the shifts in the νas(S=O) bands. SEM-EDX characterization revealed distinct post-sorption morphological changes (surface cracking and flaking) and confirmed significant REE accumulation on the resins (up to 4.04 wt.%) coupled with a stoichiometric decrease in sulfur content, validating the ion-exchange mechanism. These findings provide a deeper insight into the remote conformational effects governing interpolymer interactions and offer a highly promising approach for the selective recovery of REEs in hydrometallurgy. Full article

Rare earth elements (REEs) are predominantly separated by using mixer–settler solvent extraction technology. While this method has been utilized in the industry, it does have a few setbacks, such as requirement of large module footprint to compensate for inefficient separation. Likewise, researchers have turned to membrane separation technology to address these challenges faced by mixer–settler solvent extraction. Supported liquid membranes (SLMs) are a viable alternative in membrane separation technology as they exhibit similar conceptual designs to that of solvent extraction, albeit requiring smaller amounts of organic carrier and lower module footprint compared to mixer settler solvent extraction. In this research, the application of an electrospun membrane was explored using SLMs for the separation between light REEs (LREEs) and heavy REEs (HREEs). To do this, the study initially employs the usage of neodymium (Nd) and dysprosium (Dy) as the baseline for LREEs and HREEs, and later using real REE leachate for the separation between LREEs and HREEs. This study also investigates the effects of different pH of feed solution, organic carrier loading, and stripping concentrations. Overall, to achieve higher selectivity of Nd/Dy, a higher pH of feed solution of 5, a low loading of organic carrier at 10 wt%, and a low stripping concentration of 1 M H₂SO₄ was recommended. For the separation of LREEs and HREEs, a separation factor of 2.38 was achieved with a recovery of 10.43% of LREEs in under 60 min by using a small-scale membrane of 4 cm² effective area. Long term operation indicates a stable LREE/HREE separation performance using the optimized condition. Full article

A low-complexity Hall-based measurement system implementing a dark/illuminated differential estimator of the majority-carrier photoconductive response is assessed on n-type crystalline silicon wafers with contrasting doping concentrations. The setup combines a Van der Pauw configuration, permanent neodymium magnets, a characterized white LED source, and a source–measure unit to extract an apparent Hall-derived differential indicator—not a calibrated majority-carrier density—under dark and illuminated steady-state conditions. At $1.81\mathrm{mW}{\mathrm{cm}}^{-2}$, the lightly doped wafer ($N_D\approx {10}^{14}{\mathrm{cm}}^{-3}$) shows a resolved response ($\Delta {\sigma }_{n,H}=29.61\pm 3.406\mathrm{mS}{\mathrm{cm}}^{-1}$), reported as mean ± sample standard deviation from 15 dark/light cycles. The heavily doped wafer ($N_D\approx {10}^{17}{\mathrm{cm}}^{-3}$) gives a nominal below-threshold response ($\Delta {\sigma }_{n,H}=1.167\pm 0.140\mathrm{mS}{\mathrm{cm}}^{-1}$) from the same cycling protocol; it should be interpreted only as an unresolved trend-level indication because it lies below the instrumental detection threshold. The contrast is qualitatively consistent with the expected doping dependence, but no quantitative performance ratio is claimed for the heavily doped wafer. A Macdonald–Cuevas comparison is used only as a qualitative physical-consistency benchmark. No independent QSSPC, SSPC, $\mu$-PCD, or carrier-resolved photo-Hall measurement was available for the same wafers; therefore, the system serves as a complementary low-cost screening tool for comparative trend analysis, not a replacement for calibrated photoconductance or photo-Hall techniques, and it does not constitute a new measurement principle. Full article

Modification of DSSC photoanodes by adding various types of materials is a widely used method to improve the performance of electrochemical devices. In this work, selected rare-earth oxide (RE₂O₃) nanoparticles, such as erbium oxide (Er₂O₃), holmium oxide (Ho₂O₃), neodymium oxide (Nd₂O₃), and ytterbium oxide (Yb₂O₃), were applied for photoanode preparation. A simple method for photoanode fabrication based on the direct mixing of oxide nanoparticles with TiO₂ paste was employed. The effect of variation in the rare-earth oxide content in the photoanode was investigated. The prepared composite photoanodes were characterized by XRD and FE-SEM for structural and morphological studies. XRD verified the anatase polymorph of TiO₂; FE-SEM with EDS mapping validated the uniform morphology of the anode and the distribution of RE₂O₃, as well as its amount. The photovoltaic parameters of modified DSSCs based on the current-voltage measurements were analyzed. Full article

We present a preliminary feasibility assessment of a magnetic shield designed to protect a space probe from cosmic radiation via magnetic deflection using neodymium permanent magnets. This work is grounded in theoretical considerations whose preliminary indications are intended to serve as the basis for future Monte Carlo simulations and laboratory validation. The novelty of our approach lies in the use of a magnetic shield; its competitiveness with conventional passive absorbing shielding is not investigated here but warrants dedicated future work. The primary objective is to protect a spacecraft from the flux of charged particles emitted by the Sun. To this end, we combine theoretical modeling and numerical simulations, followed by the construction of a prototype for laboratory testing and, potentially, for future experimental validation at the CubeSat scale. Full article

Rare earth element-related occupational and environmental health risks have received increasing attention, but the molecular mechanisms underlying neodymium oxide (Nd₂O₃)-induced pulmonary fibrosis remain unclear. This study aimed to identify potential targets, metabolites, and pathways involved in fibrosis-related lung responses after Nd₂O₃ exposure. An integrated network toxicology and metabolomics approach was combined with an in vivo mouse model of Nd₂O₃-induced pulmonary toxicity. Histopathological injury, collagen deposition, and fibrosis-related protein expression were evaluated by HE staining, Masson staining, and Western blotting, respectively. Candidate targets were identified from public databases, key pathways were analyzed through network construction, and selected genes were validated by RT-qPCR. Nd₂O₃ exposure caused evident lung injury, inflammatory cell infiltration, structural disruption, increased collagen deposition, and elevated fibrosis-related protein expression. A total of 162 overlapping targets related to Nd₂O₃ exposure and pulmonary fibrosis were identified. ESR1, PTGS2, HSP90AA1, and MMP9 emerged as key targets, while cAMP signaling, arachidonic acid metabolism, PI3K-Akt signaling, and efferocytosis-related processes were implicated. Metabolomics showed distinct separation between control and high-exposure groups, with differential metabolites mainly associated with lipid metabolism and inflammation. RT-qPCR further confirmed altered expression of key genes. These findings suggest that Nd₂O₃ may promote fibrosis-related lung responses through inflammatory signaling, lipid metabolic disturbance, and profibrotic pathway activation. Full article