Rare Earth Research Articles

The rare-earth elements recovered from the leachate of discarded phosphor by electrodeposition

ABSTRACT Recovering rare-earth elements (REEs) from discarded phosphors is an important solution to alleviate the current shortage of rare-earth resources, the aluminum element in discarded phosphors will badly affect the purity and recovery of rare-earth elements. An electrodeposition method for recovering the rare earth from the discarded phosphoric leachate was proposed to avoid the effecting of aluminum elements. The results show that the purity of the rare-earth oxides recovered reached 99.13% and the recovery rate of rare-earth elements reached 98.89% by adopting the optimal electrodeposition process with the help of the complexing agent glycine. Research has found that adding the complexing agent glycine can help rare-earth hydroxides precipitate at the cathode and inhibit aluminum ion precipitation by changing the aluminum deposition potential. Moreover, it was also found that the generation of OH- ions by reduction of NO3- in acid aqueous solution was a one-step irreversible reaction in the deposition process by cyclic voltammetry, which ensured the reliability of rare-earth hydroxide precipitation reaction.

Characterization of regolith-hosted rare earth element deposits using reflectance spectroscopy: Framework towards an efficient and reliable field exploration tool

With a growing demand for the rare earth elements (REE), exploration of regolith-hosted REE resources worldwide has been thriving in recent years and development of a rapid and reliable field-based tool will greatly facilitate the survey and exploration. In this study, we use visible and short-wave infrared (VNIR-SWIR) reflectance spectroscopy to comprehensively evaluate the applicability of the technique to explore regolith-hosted REE resources, exemplified by three representative regolith-hosted REE deposits in China. Neodymium among the REE shows reliably detectable spectral features in the VNIR-SWIR spectroscopy down to concentrations of 10–50 ppm in field samples with heterogeneous mineral grain sizes. The Nd spectral intensity of electronic transition at the band of ∼800 nm is correlated with bulk Nd concentrations and can be used as semi-quantitative indicators for the Nd concentrations, thereby the total REE in regolith. Moreover, VNIR-SWIR spectroscopy is demonstrated to be capable of delineating favorable ore-bearing mineralogy by characterizing the abundance and type of clay minerals and Fe (oxyhydr)oxides, and the crystallinity of kaolinite-group minerals. However, the Nd spectral features of samples with high bulk Fe2O3 contents (>3 wt%) are significantly masked due to overlapping by the strong absorption features of ferric (oxyhydr)oxides. VNIR-SWIR spectroscopy is deemed to be applicable to the exploration of regolith-hosted REE resources developed from Fe-poor felsic rocks.

Sediment-Hosted Rare-Earth Elements Mineralization from the Dian-Qian District, Southwest China: Mineralogy and Mode of Occurrence

The Xuanwei Formation’s claystones in the Dian-Qian District of Southwest China are rich in rare-earth elements (REEs), suggesting their potential as a source of medium and heavy rare earths. However, the REE content in these rocks is lower than other types of rare-earth deposits, and the interrelationship among clay minerals is intricate. There is no direct evidence indicating the mineralization of REEs, limiting their beneficiation and extraction. The objective of this study is the characterization of REE distribution in the Dian-Qian District. The sedimentary rocks in this district are mainly composed of kaolinite, boehmite, quartz, rutile, and pyrite. The results of continuous chemical extraction of REE-rich claystone and transmission electron microscope (TEM) observations have confirmed that REEs occurred as florencite in the rocks, and that the ion-absorption state makes only a negligible contribution to the REE content. A close relationship between florencite and kaolinite makes traditional mineral processing operations very difficult. Combined with the properties of kaolinite, roasting-acid leaching was the efficacious approach for rare-earth resources extracted from the rare earth-rich clay rocks of the Xuanwei Formation.

Enhanced deep-water circulation facilitated rare earth elements enrichment in pelagic sediments from the northwestern Pacific Ocean

The lack of knowledge about the enrichment mechanism of rare earth elements and yttrium (REY) in deep-sea sediments is impeding the development of theories and exploration strategies for pelagic REY-rich sediments. Ocean circulation variability seems to be crucial in enriching REY in pelagic sediments, which, however, has not been extensively studied. Here, we examined the Pb-Nd isotopic signals of bottom water recorded by the authigenic ferromanganese oxyhydroxide fractions, as well as the Mn/Al and Mn/Ti ratios of bulk samples from a well-dated sediment core in the northwestern Pacific Ocean. These proxies consistently indicate that enhanced deep-water circulation occurred in the study area at ∼11.5–9.5 Ma, which was most likely to be caused by changes in the flow path of bottom currents. The age of this distinct event consists with the forming age of highly REY-rich sediments. We propose that enhanced deep-water circulation in seamount areas could increase the flux of micronodules and fish debris into the pelagic sediments, facilitating the scavenging of REY from seawater. Our findings establish a connection between enhanced deep-water circulation and the enrichment of REY in pelagic sediments.

Investigation of the structural, thermo–electrical, and morphological properties of the Bi2O3 ceramics co–doped with rare earths

Investigation of the structural, thermo–electrical, and morphological properties of the Bi2O3 ceramics co–doped with rare earths

Inducing high-concentration Tb3+ with free oxygen via atomic layer deposition

Precise preparation and control of trivalent states in rare earth metal oxide films are crucial for their optical and magnetic applications. In this study, compact and continuous terbium-doped nanofilms were deposited on silica substrates using atomic layer deposition (ALD). The average nanoparticle size varied from 17.9 to 78.5 nm with increasing growth cycles. X-ray photoelectron spectroscopy showed that the Tb3+/Tb4+ ratio increased from 0.98 to 1.42. A valence reduction mechanism involving free oxygen was introduced to analyze the reasons for the enhanced Tb3+ concentration in the nanofilms. The enhanced photoluminescence of Tb3+ (5D4→7F5) ions and the increased magnetization in terbium oxide nanofilms both reveal that free oxygen ions are the effective active sites responsible for the transition from the tetravalent to the trivalent state, in excellent agreement with theoretical analysis. Size control and free oxygen induction are promising strategies for enhancing the optical and magnetic properties of multivalent rare earth oxides.

Fluorine Doping Mediated Epitaxial Growth of NaREF4 on TiO2 for Boosting NIR Light Utilization in Bioimaging and Photodynamic Therapy

AbstractBy integrating TiO2 with rare earth upconversion nanocrystals (NaREF4), efficient energy transfer can be achieved between the two subunits under near‐infrared (NIR) excitation, which hold tremendous potential in the fields of photocatalysis, photodynamic therapy (PDT), etc. However, in the previous studies, the combination of TiO2 with NaREF4 is a non‐epitaxial random blending mode, resulting in a diminished energy transfer efficiency between the NaREF4 and TiO2. Herein, we present a fluorine doping‐mediated epitaxial growth strategy for the synthesis of TiO2‐NaREF4 heteronanocrystals (HNCs). Due to the epitaxial growth connection, NaREF4 can transfer energy through phonon‐assisted pathway to TiO2, which is more efficient than the traditional indirect secondary photon excitation. Additionally, F doping brings oxygen vacancies in the TiO2 subunit, which further introduces new impurity energy levels in the intrinsic band gap of TiO2 subunit, and facilitates the energy transfer through phonon‐assisted method from NaREF4 to TiO2. As a proof of concept, TiO2‐NaGdF4 : Yb,Tm@NaYF4@NaGdF4 : Nd@NaYF4 HNCs were rationally constructed. Taking advantage of the dual‐model up‐ and downconversion luminescence of the delicately designed multi‐shell structured NaREF4 subunit, highly efficient photo‐response capability of the F‐doped TiO2 subunit and the efficient phonon‐assisted energy transfer between them, the prepared HNCs provide a distinctive nanoplatform for bioimaging‐guided NIR‐triggered PDT.

Complexation of ThoriumIV with Fluorinated Heterocyclic β‐Diketones in Aqueous Hydrochloric Solutions

AbstractThe interaction of Thorium(IV) with a group of non‐symmetric CF3‐diketones has been studied by means of electronic absorption spectroscopy in HCl aqueous solutions at I=0.5 M (NaCl) and T=298 K. Six heterocyclic dicarbonyl ligands (2‐thenoyl‐trifluoroacetone, 2‐furoyl‐trifluoroacetone, 2‐selenophen‐trifluoroacetone, 2‐tellurophen‐trifluoroacetone, phenyl‐trifluoroacetone, and 2‐naphthyl‐trifluoroacetone) demonstrate the chelation activity toward ThIV in the acidic pH range. Obtained values of the “true” stability constants lie in the range 6.2–6.8 logarithmic units, respectively. A significant (10–15 nm) bathochromic shift between the maximum absorption wavelength of lanthanide and actinide monocomplexes has been detected. Observed spectral shift increases with the atomic number of substituted chalcogen atoms in the heterocyclic ring of the corresponding ligand: 10 nm for furan, 11 nm for thiophen, 14 nm for selenophen, and 15 nm for tellurophene rings. The complexation with Thorium occurs in an acidic media, where studied ligands do not interact with transition and rare earth metals. Spectral and pH shifts make studied ligands useful reagents for the detection and analytical determination of Thorium in the mixture with other metals without prior separation. Quantum‐chemical simulations (DFT and TD‐DFT) demonstrate that the nine‐ and deco‐coordinated structures of ThoriumIV complexes reproduce experimental values within reasonable errors.

Anchoring gadolinium oxide nanoparticles onto CuInZnS: Efficient photocatalytic tetracycline degradation and mechanism analysis

Photocatalysis technology is one of the potential methods to remit the growing issues of environmental pollution. It is of great significance to rationally design high performance antibiotic wastewater degradation catalysts in the whole pH range. In this experiment, Gd2O3 nanoparticles (GdO NPs) were successfully grown onto CuInZnS (CIZS) by a simple hydrothermal method. The introduction of GdO has obvious effects on the nanosheet thickness of CIZS, which reduces carrier transport distances and improves the active sites number of CIZS. What’s more, the SO4•- absorption and electron transfer ability are also greatly optimized. Under 300 W Xe light, tetracycline can be efficient degraded more than 93 % in the whole pH range, which presents absolute advantage compared to CIZS and GdO. Based on the combination of experimental characterization and density functional theory calculations, the proposed photocatalytic tetracycline degradation pathway and mechanism have been given. Moreover, the results of toxicity analysis proved that the CIZS-GdO catalyst could successfully reduce the toxicity of tetracycline wastewater. This work has reference value for the application of rare earth oxides in the field of photocatalysis at full pH range.

Antisolvent crystallization of rare earth sulfate hydrates: Thermodynamics, kinetics and impact of iron

The thermodynamics and kinetics of ethanol antisolvent crystallization of rare earths from sulfate solutions has been explored, with a view towards separating the rare earths as part of a NdFeB magnet recycling process. The solubility of single and binary metal (Nd, Pr, Fe) phases in aqueous ethanol solutions has been determined. The impact of Fe and Pr on the crystallization of Nd is evaluated, the oxidation kinetics of Fe(II) to Fe(III) quantified, and the influence of Fe oxidation state on the thermodynamics and kinetics of crystallization investigated. Oxidation to Fe(III) is slow, with a half life of approx. 600 h. For pure Nd, the solubility of the obtained, stable sulphate octahydrate decreases exponentially with increased molar organic:aqueous (O/A) ratio, and is well described by the OLI model until O/A=0.2. Pr crystallizes as an isostructural octahydrate with similar solubility. Fe(II) precipitates as a mixed solid phase, with a solubility approximately 40 times higher than the rare earths at O/A=0.2. Fe(III) solutions exhibit liquid–liquid phase separation without precipitation at all evaluated concentrations. Nd and Pr coprecipitate together in proportion to their relative concentrations, with Pr precipitating at concentrations well below its pure component solubility. Fe(II) does not precipitate with Nd at O/A≤0.2 even at high concentration, with significant precipitation as separate particles at higher O/A for all concentrations. The crystallization kinetics and the morphology of the Nd phase is affected by the Fe oxidation state. The work highlights the potential of antisolvent crystallization for selective and efficient separation of REE from Fe.

Oxygen ion diffusion in RE3TaO7: Why long-range migration of O2− is prohibited in the defective-fluorite structure?

Oxides with low O2− lattice diffusion rate are critical for the development of topcoat materials for next generation thermal barrier coatings (TBCs) working at > 1600 °C to prevent the fast growth of thermally grown oxide (TGO) at the bondcoat/topcoat interface. Here we delve into a comprehensive analysis of the oxygen ion transport characteristics of the recently developed low-, medium- and high-entropy rare earth tantalates (RE3TaO7) for TBCs by a combination of impedance spectroscopy, 18O isotope diffusion tests and atomic-scale simulations. Results show that the RE3TaO7 series display remarkably low oxygen ion diffusion rate (> 3 orders of magnitude lower than the state-of-the-art topcoat material yttria stabilized zirconia, YSZ) despite the presence of abundant oxygen vacancies in the structure. Molecular dynamic (MD) simulations combined with first principles calculations reveal that oxygen ions are strongly trapped by the potential well at the Ta-Ta edge in the tantalates. In addition, the high electrostatic potential (EP) surrounding oxygen vacancies and the high diffusion barriers between rare earth elements also impede oxygen ion diffusion. With low oxygen ion diffusion rate, along with exceptional thermal and mechanical properties reported previously, RE3TaO7 are promising topcoat materials for next-generation TBCs working at higher temperatures. Moreover, this study also provides valuable insights for understanding the O2− lattice diffusion behaviour in RE3TaO7 with a defective fluorite structure, which may benefit the exploration of oxide-ion conductors.

Assessment of potential toxic elements in soils, sediments, and vegetation in the surroundings of Anapa, Russia.

The study presented here reports the concentration of major, trace, and rare earth elements in soil, sediments, and vegetation samples collected from 13 locations around Anapa City located on the northern coast of the Black Sea in Russia. The neutron activation analysis technique has been used to fulfill this objective. Along with this, the bioconcentration and translocation factors were calculated. Overall, the content of 31 elements was detected in soil and sediments while 20 elements were determined in three types of vegetation: macroalgae (Cystoseira sp. and Ulva sp.), aquatic plants (Phragmites australis), and sea grass (Zostera sp.). The quantified concentration followed the order soil > sediment > vegetation. The phytotoxic levels for Zn, V, Mn, and Fe have been quantified as the highest. Bromine was the most abundant and accumulated in Phragmites australis. Based on the results obtained from this investigation, there is a possibility of contamination in the study area.

Synthesis of Rare Earth Metal Complexes Stabilized by Amine Bridged Bis(phenolato) Ligands and Their Performance in the Polymerization of rac-β-Butyrolactone.

A series of rare earth alkoxides bearing amine-bridged bis(phenolato) ligands were synthesized through sequential reactions of RE(C5H5)3(THF) (RE = Y, Lu) or Nd[N(SiMe3)2]3 with bis(phenols) LH2 and CF3CH2OH. Complexes REL(OCH2CF3)(THF)n (1-6) bearing different aryl-substituents were obtained in good yields of 59-70%. They were applied in the ring-opening polymerization (ROP) of rac-β-butyrolactone (rac-BBL), which showed good activity (TOF up to 27,300 h-1), resulting in syndiotactically enriched poly(3-hydroxybutyrate) (PHB) (Pr up to 0.86) with narrow polydispersities (PDI ≤ 1.27). The yttrium complex 3 bearing bulky o-1,1-diphenylethyl substituents outperformed other complexes, suggesting that the smaller ionic radii of metal centers and bulky ortho substituents of ancillary ligands play crucial roles in controlling the activity and stereoselectivity in ROP of rac-BBL. Kinetics of the polymerization of rac-BBL initiated by complex 3 was investigated, which revealed first order dependences on the monomer and initiator concentrations, respectively.

Mg-modified layered erbium hydroxides promoting glucose transformation to lactic acid

Layered rare earth hydroxides (LREHs) with unique layer structure and tunable properties have shown attractive potentials as heterogeneous catalyst, but is still challenging in biomass valorization towards valuable chemical production due to the poor catalytic activity. Herein, Mg-modified erbium hydroxides (Mg-LErHs) with well-constructed layered structure have been first fabricated, where the properties and structure of Mg-LErHs significantly depend on the proportion of Mg. The results of catalyst characterizations reveal that Mg introduction increases the interlayer spacing and the content of Er(III)-O. Mg modification also hinders the desorption of crystallized H2O and dehydroxylation, thereby increasing the degree of crystallinity and promoting the stability of the catalyst. The activity test indicate that Mg modification greatly promotes the production of lactic acid from monosaccharides, where Mg(5.8)-LErHs affords the highest lactic acid yield of 60.9 %. Mg-LErHs also outperform other Mg-LREHs catalysts for the production of lactic acid. The highest catalytic activity of Mg(5.8)-LErHs are possibly attributed to its highest degree of crystallinity, and the increased layer spacing after Mg modification might have an advantage in facilitating the entry of substrate. The increased Er(III)-O content with high Lewis acidity might facilitate the combination with electronic-rich carbonyl oxygen in substrate. This research may provide a novel strategy to design the layered rare earth catalysts with tunable catalytic activity for biomass valorization.

Leaching Behavior and Leaching Mechanism Analysis of Pb in Soil Under the Action of Sulfate Leaching Agent: A Case Study of Ion-Adsorption Rare Earth Mining Area

Leaching Behavior and Leaching Mechanism Analysis of Pb in Soil Under the Action of Sulfate Leaching Agent: A Case Study of Ion-Adsorption Rare Earth Mining Area

Fluorine Doping Mediated Epitaxial Growth of NaREF4 on TiO2 for Boosting NIR Light Utilization in Bioimaging and Photodynamic Therapy.

By integrating TiO2 with rare earth upconversion nanocrystals (NaREF4), efficient energy transfer can be achieved between the two subunits under near-infrared (NIR) excitation, which hold tremendous potential in the fields of photocatalysis, photodynamic therapy (PDT), etc. However, in the previous studies, the combination of TiO2 with NaREF4 is a non-epitaxial random blending mode, resulting in a diminished energy transfer efficiency between the NaREF4 and TiO2. Herein, we present a fluorine doping-mediated epitaxial growth strategy for the synthesis of TiO2-NaREF4 heteronanocrystals (HNCs). Due to the epitaxial growth connection, NaREF4 can transfer energy through phonon-assisted pathway to TiO2, which is more efficient than the traditional indirect secondary photon excitation. Additionally, F doping brings oxygen vacancies in the TiO2 subunit, which further introduces new impurity energy levels in the intrinsic band gap of TiO2 subunit, and facilitates the energy transfer through phonon-assisted method from NaREF4 to TiO2. As a proof of concept, TiO2-NaGdF4 : Yb,Tm@NaYF4@NaGdF4 : Nd@NaYF4 HNCs were rationally constructed. Taking advantage of the dual-model up- and downconversion luminescence of the delicately designed multi-shell structured NaREF4 subunit, highly efficient photo-response capability of the F-doped TiO2 subunit and the efficient phonon-assisted energy transfer between them, the prepared HNCs provide a distinctive nanoplatform for bioimaging-guided NIR-triggered PDT.

Reversible photochromic effect and excellent mechanical properties of Nd3+-doped Zr6Nb2O17 purple ceramics

The development of colored ceramics is limited because it can only display a single color. Therefore, colored ceramics that can achieve reversible switching between two different colors can make up for this deficiency. In this study, we report a novel rare-earth doped colored ceramic, Zr6Nb2O17: xNd3+ (abbreviated as ZNO: xNd), which has been successfully obtained with good mechanical and photochromic properties of purple ceramics by component adjustment. The doping of rare earth Nd3+ ions changed the color of the ceramic matrix from light curry to light purple, and more importantly, enhanced its mechanical properties, with optimal Vickers hardness and fracture toughness values of 16.53 GPa and 5.2 MPa·m1/2, respectively. Alternating 365 nm irradiation and 350°C thermal stimulation, the ceramic samples exhibited good photochromic properties, with the highest photochromic contrast of 21.1 %, and good reversibility and cyclic stability. Finally, it is important to clarify that the photochromic mechanism is mainly caused by the formation of color centers resulting from electrons or holes being trapped by intrinsic or extrinsic defects. These results indicate that ZNO: xNd purple ceramics can be applied in the field of colored ceramics and provide a new path for the development of rare earth-colored ceramics.

Highly Efficient and Precise Rare-Earth Elements Separation and Recycling Process in Molten Salt

Owing to the worldwide trend towards carbon neutrality, the number of Dy-containing heat-resistant Nd magnets used for wind power generation and electric vehicles is expected to increase exponentially. However, rare earth (RE) elements (especially Dy) are unevenly distributed globally. Therefore, an environmental-friendly recycling method for RE elements with a highly precise separation of Dy and Nd from end-of-life magnets is required to realize a carbon-neutral society. As an alternative to traditional hydrometallurgical RE separation techniques with a high environmental load, we designed a novel, highly efficient, and precise process for the separation and recycling of RE elements from magnet scrap. As a result, over 90% of the RE elements were efficiently extracted from the magnets using MgCl2 and evaporation loss was selectively suppressed by adding CaF2. The extracted RE elements were electrolytically separated based on the formation potential differences of the RE alloys. Nd and Dy metals with purities greater than 90% were estimated to be recovered at rates of 96% and 91%, respectively. Almost all the RE in the scraps could be separated and recycled as RE metals, and the byproducts were easily removed. Thus, this process is expected to be used on an industrial scale to realize a carbon-neutral society.

Mobility and fractionation of rare earth elements during black shale weathering: Implications from acid rock drainage and sequential extraction study

Black shale is a type of sedimentary rocks that are enriched in rare earth elements (REEs). It is of both economic importance and environmental significance to understand REE mobility during black shale weathering. The present study approaches to this by analysing REEs in acid rock drainage (ARD) from black shale weathering system, fresh and weathered black shales, soils derived from black shales, and sequential extractants from black shales at Dongping town in Hunan province (China). Results showed that REEs had variable high concentrations in ARD as shown by total REE + Y (∑REY) concentrations from 162 to 4074 (μg/L). REEs in ARD displayed hat-shape NASC-normalized patterns with significant enrichments of middle REEs (MREE) relative to light REEs (LREE) and heavy REEs (HREE), and had significant negative Ce (Ce/Ce⁎ = 0.6) and positive Y (Y/Y⁎ = 1.5) anomalies. MREE enrichment in ARD could be evaluated using MREE/MREE⁎ values, which varied from 1.43 to 1.81 with a mean of 1.65, distinctly higher than those of whole rocks (around 1.0). 1 M HCl extraction results suggested that REEs were integratedly mobilized during shale weathering, while six-step extraction studies identified that REEs in ARD resulted from exchangeable and Fe-oxide fractions with MREE and HREE enrichment in shales respectively. MREE in exchangeable and HREE in Fe-oxide fractions were preferentially released during weathering, as illustrated by plots of MREE/MREE⁎ against HREE/LREE ratios of ARD and six-step extractants. Therefore, geochemical processes for REE mobility during black shale weathering included integrated mobilization and preferential release. Integrated REE mobilization resulted from the dissolution of REE-bearing minerals and oxidation of sulfides. Preferential REE release resulted from acid fluids produced by sulfide oxidation during weathering. Thus, a new model was proposed for interpreting geochemical processes of REE mobility during black shale weathering, and for understanding REE distribution in ARD from natural and anthropogenic systems.

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 (CaCl2.2H2O) pre-treatment process followed by water leaching, acid leaching (0.5M HCl, S/L =1/10g/ml, 90 °C, 3h), oxalic acid precipitation and calcination (850 °C, 2h) 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 (30-120min) on the rare earth dissolution. The theoretical activation energy for the chloridizing roasting process is estimated as 22.3 (OFW) and 16.7kJ/mol (KAS), while the experimental activation energy for Nd and Dy dissolution was determined to ~29.3 and ~17.7kJ/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, 90min, 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 1kg of NdFeB powder can yield ~285g of rare earth oxides (~239g Nd2O3, ~14g Dy2O3) with 96% purity. Further, this study demonstrates that using CaCl2.2H2O 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.