Recycling Of Rare Earth Elements Research Articles

Study on Properties of Micro-Nano Magnetic Composite Prepared by Mechanochemical Method of NdFeB Secondary Waste and Removal of As (V) from Mine Water

The secondary waste produced by NdFeB waste after rare earth recycling, with an annual output of more than tens of thousands of tons, is the largest solid waste emission source in the rare earth industry, and long-term storage causes land resource occupation and environmental pollution. Arsenic-containing mine wastewater has serious harm, wide distribution, and long duration of pollution. In this study, the mechanical ball milling method was used to activate NdFeB secondary waste to prepare micro-nano magnetic composite materials, the main components of which are Fe2O3, Fe3O4, and C. Under mechanical mechanochemical action, the particles are more dispersed, the particle size decreases, the specific surface area increases significantly, the crystal structure changes to amorphous structure, the degree of amorphous shape increases, and the content of Fe-OH increases. Applied to the treatment of As (V) in simulated mine water, it was found that the removal of As (V) by this material was mainly based on chemisorption and monolayer adsorption, and the maximum adsorption amount reached 10.477 mg/g. Zeta, FT-IT, and XPS characterization confirmed that the removal of As (V) was a coordination exchange reaction between the material and As (V) to form an inner sphere complex. The removal rate of As (V) decreased from 94.33% to 73.56% when the initial concentration of solution was 10 mg/L, pH value was 3.0, and material dosage was 1 g/L after 5 times of regrowth. This study provides a new way for the application of NdFeB secondary waste, which has low cost, green environmental protection, and wide application prospects.

Phosphorylated porous phenolic resin for efficient extraction of low-concentration rare earth elements from tailing wastewater

Efficient extraction and recycling of rare earth elements (REEs) from low-concentration complex tailing wastewater is critical to meeting the growing industrial demands and optimizing resource utilization. In this work, three phosphorylated porous phenolic resins (PO-PPRs) were prepared via the phosphorylation of phenolic hydroxyl groups with POCl3, and employed to extract REE3+ from both simulated and practical low-concentration REE3+-containing aqueous solution. The PO-PPRs, characterized by hierarchical pore structures, exhibit high adsorption capacities for both light and heavy REE3+ ions over a broad pH working range from 3.0 to 7.0, along with fast adsorption kinetics (<30 min). And the maximum adsorption capacities of PO-PPRs for Nd3+, Dy3+ and Y3+ were found to be 104.1, 118.0 and 63.9 mg/g, respectively. Furthermore, the introduction of phosphonic groups significantly improves the REE3+ adsorption selectivity against various interfering metal ions such as Na+, K+, Ca2+, Mg2+, and Al3+. For instance, the Nd3+/Al3+ separation factor (S.F.) of 24 exceeded that of most commercial resins and reported materials. In a simulated mixed multi-element aqueous solution system containing Nd3+, Dy3+, Y3+, Al3+, Ca2+, Mg2+, Mn2+, K+ and Na+, PO-PPR-1 extracted 82.5% of total REE3+ while maintaining Al3+ adsorption efficiency of less than 13%. Moreover, the extraction efficiency of total REE3+ for PO-PPR-1 in pretreated practical wastewater from ion-adsorbed ores tailing reached 99.6%. Additionally, PO-PPRs demonstrated easy regeneration and excellent recycling performance after 5 consecutive adsorption–desorption cycles, confirming their promising application potential in low-concentration REEs extraction.

Quantifying provincial in-use stocks of rare earth to identify urban mining potentials in the Chinese mainland

Recycling of rare earth elements (REE) can help to offset the increasing demand for REE minerals and enhance the diversification of the REE supply chain. The development of low-carbon technologies, such as new energy vehicles and wind turbines has expedited the accumulation of REE as “urban mines”. This trend offers prospects for the progress of REE recycling initiatives targeting end-of-life products. This study conducts a dynamic material flow analysis (combined top-down and bottom-up method) of nine products containing NdFeB permanent magnets (their scrap is regarded as the most important secondary resource of rare earth) in the Chinese mainland at a provincial level to identify end-of-life products and provinces with high urban mining potentials. Results indicate that e-bikes, wind turbines, and air conditioners have the most significant REE recycling potentials in the Chinese mainland. Provinces with large populations and robust economies, such as Guangdong and Jiangsu, exhibit greater potential for REE recycling. This study illustrates significant provincial disparities in the end-of-life recycling potentials of REEs in the Chinese mainland and highlights the significance of provincial-level assessments of urban mining potential in the planning of the REE recycling industry.

Identification of yttrium oxide-specific peptides for future recycling of rare earth elements from electronic scrap.

Yttrium is a heavy rare earth element (REE) that acquires remarkable characteristics when it is in oxide form and doped with other REEs. Owing to these characteristics Y2 O3 can be used in the manufacture of several products. However, a supply deficit of this mineral is expected in the coming years, contributing to its price fluctuation. Thus, developing an efficient, cost-effective, and eco-friendly process to recover Y2 O3 from secondary sources has become necessary. In this study, we used phage surface display to screen peptides with high specificity for Y2 O3 particles. After three rounds of enrichment, a phage expressing the peptide TRTGCHVPRCNTLS (DM39) from the random pVIII phage peptide library Cys4 was found to bind specifically to Y2 O3 , being 531.6-fold more efficient than the wild-type phage. The phage DM39 contains two arginines in the polar side chains, which may have contributed to the interaction between the mineral targets. Immunofluorescence assays identified that the peptide's affinity was strong for Y2 O3 and negligible to LaPO4 :Ce3+ ,Tb3+ . The identification of a peptide with high specificity and affinity for Y2 O3 provides a potentially new strategic approach to recycle this type of material from secondary sources, especially from electronic scrap.

Separation of rare earth elements from waste NdFeB magnets: The influence of hematite seeds and agents on the hematite precipitation in nitric acid medium

ABSTRACT Nowadays with the evolution of technology and rare earth elements (REE) are raw materials for a multitude of products, especially in technological applications. Large amounts of electronic waste rich in REE are produced, and this can be utilized as a valuable resource. For these reasons, efforts and research are focusing on secondary production, which is recycling and recovery of REE and specifically neodymium (Nd) from end-of-life components. In this study, the recovery of REE from NdFeB was investigated based on Box-Behnken experimental design technique. The effect of the experimental parameters in the hydrolysis of Fe3+ to hematite in a nitric acid medium in the hydrothermal reactor was examined in detail. Afterwards, the influence of the temperature, time, and hematite precipitation agents including starch (C6H10O5) n, sucrose (C12H22O11), and hematite seeds (Fe2O3) on the recovery of REE, and hematite precipitation were analyzed by statistical analyses. The optimal parameters for maximum REE recovery and iron removal under pressure and temperature were determined to be a process temperature of approximately 145°C, a process time of approximately 6 hours with the starch addition. The optimum parameters are in harmony with the validation experiments.

The paradox of waste geography? Dynamic evolution and quality evaluation of the global rare earth recycling trade network

Recycling trade has become an important initiative for major powers to address rare earth supply risks. With the help of recycling quality evaluation model, competitive intensity model, complex network method, and GIS analysis, the dynamics and characteristics of the global rare earth recycling trade network are revealed in this study. The results show that the global rare earth recycling market is closely related to the development of the product trade market and shows repeated fluctuations. China was the largest importer, while the U.S. was the most important bridge and replaced the Philippines as the largest exporter. Rare earth recycling is a classic paradox of waste geography, developed countries in general have replaced developing countries as the main buyers and are at the core of the network, forming a juxtaposition of two major associations, East and West. In terms of spatial dynamics, the global rare earth recycling trade network has gradually formed a polycentric system with Europe, America (the U.S., Brazil) and East Asia (China, the Philippines, and Japan). Global competition for rare earth recycling has also gradually shifted from intra-Asia to Europe and the America, but China's recycling quality is higher than other major powers.

Intelligent leaching rare earth elements from waste fluorescent lamps.

Rare earth elements (REEs), one of the global key strategic resources, are widely applied in electronic information and national defense, etc. The sharply increasing demand for REEs leads to their overexploitation and environmental pollution. Recycling REEs from their second resources such as waste fluorescent lamps (WFLs) is a win-win strategy for REEs resource utilization and environmental production. Pyrometallurgy pretreatment combined with acid leaching is proven as an efficient approach to recycling REEs from WFLs. Unfortunately, due to the uncontrollable components of wastes, many trials were required to obtain the optimal parameters, leading to a high cost of recovery and new environmental risks. This study applied machine learning (ML) to build models for assisting the leaching of six REEs (Tb, Y, Eu, La, and Gd) from WFLs, only needing the measurement of particle size and composition of the waste feed. The feature importance analysis of 40 input features demonstrated that the particle size, Mg, Al, Fe, Sr, Ca, Ba, and Sb content in the waste feed, the pyrometallurgical and leaching parameters have important effects on REEs leaching. Furthermore, their influence rules on different REEs leaching were revealed. Finally, some verification experiments were also conducted to demonstrate the reliability and practicality of the model. This study can quickly get the optimal parameters and leaching efficiency for REEs without extensive optimization experiments, which significantly reduces the recovery cost and environmental risks. Our work carves a path for the intelligent recycling of strategic REEs from waste.

Stripped: contribution of cyanobacterial extracellular polymeric substances to the adsorption of rare earth elements from aqueous solutions.

The transformation of modern industries towards enhanced sustainability is facilitated by green technologies that rely extensively on rare earth elements (REEs) such as cerium (Ce), neodymium (Nd), terbium (Tb), and lanthanum (La). The occurrence of productive mining sites, e.g., is limited, and production is often costly and environmentally harmful. As a consequence of increased utilization, REEs enter our ecosystem as industrial process water or wastewater and become highly diluted. Once diluted, they can hardly be recovered by conventional techniques, but using cyanobacterial biomass in a biosorption-based process is a promising eco-friendly approach. Cyanobacteria can produce extracellular polymeric substances (EPS) that show high affinity to metal cations. However, the adsorption of REEs by EPS has not been part of extensive research. Thus, we evaluated the role of EPS in the biosorption of Ce, Nd, Tb, and La for three terrestrial, heterocystous cyanobacterial strains. We cultivated them under N-limited and non-limited conditions and extracted their EPS for compositional analyses. Subsequently, we investigated the metal uptake of a) the extracted EPS, b) the biomass extracted from EPS, and c) the intact biomass with EPS by comparing the amount of sorbed REEs. Maximum adsorption capacities for the tested REEs of extracted EPS were 123.9-138.2 mg g-1 for Komarekiella sp. 89.12, 133.1-137.4 mg g-1 for Desmonostoc muscorum 90.03, and 103.5-129.3 mg g-1 for Nostoc sp. 20.02. A comparison of extracted biomass with intact biomass showed that 16% (Komarekiella sp. 89.12), 28% (Desmonostoc muscorum 90.03), and 41% (Nostoc sp. 20.02) of REE adsorption was due to the biosorption of the extracellular EPS. The glucose- rich EPS (15%-43% relative concentration) of all three strains grown under nitrogen-limited conditions showed significantly higher biosorption rates for all REEs. We also found a significantly higher maximum adsorption capacity of all REEs for the extracted EPS compared to cells without EPS and untreated biomass, highlighting the important role of the EPS as a binding site for REEs in the biosorption process. EPS from cyanobacteria could thus be used as efficient biosorbents in future applications for REE recycling, e.g., industrial process water and wastewater streams.

Sensitive determination of rare earth elements in liquid samples by spatial confinement assisted surface enhanced laser-induced breakdown spectroscopy

The rapid determination of rare earth elements (REEs) in liquid samples holds significant importance for various applications such as the exploration and development of REEs resources, quality control of the extraction process, regeneration and recycling of REEs, and monitoring of nuclear industry wastewater. This study employed spatial confinement assisted surface-enhanced laser-induced breakdown spectroscopy (SC-SE-LIBS) for REEs determination in liquid samples. Investigations were conducted into the impact of different material substrates, sample pretreatment methods, and spatial confinement cavity diameters on detection performance. The results reveal that the graphite substrate yields superior spectral signal intensity compared to other materials (Zn, Al, and Ni). The groove-constrained liquid–solid conversion (GCLSC) pretreatment method significantly enhances spectral stability and detection accuracy. The most favorable signal enhancement is achieved using a cylindrical spatial confinement cavity (CSCC) with an 8 mm diameter. Employing the optimized experimental conditions, quantitative analysis of six REEs (La, Ce, Pr, Nd, Gd, Y) in liquid samples was performed using analytical lines at wavelengths of La Ⅱ 394.91 nm, Ce Ⅱ 401.24 nm, Gd Ⅱ 404.99 nm, Nd Ⅱ 406.11 nm, Pr Ⅱ 417.94 nm, and Y Ⅱ 488.37 nm. The obtained calibration curves exhibited R2 fit coefficients above 0.99, with corresponding limits of detection (LoDs) of 0.021 μg/mL, 0.104 μg/mL, 0.312 μg/mL, 0.241 μg/mL, 0.036 μg/mL, and 0.045 μg/mL, respectively.

LTA zeolite particles functionalized with nanomagnetite for effective recovery of dysprosium from liquid solutions

Rare earth elements (REEs) as Dysprosium (Dy) are critical elements for the fabrication of components in many green energy technologies, from electric vehicles to wind turbines. Consequently, there is an increasing interest in creating sustainable and effective materials for the recovery and recycling of these elements. Zeolite materials have demonstrated a high affinity and selectivity for REEs. Thus, this paper aims to study the use of a synthetic LTA zeolite functionalized with nanomagnetite for Dy absorption, including a complete characterization of the synthetic zeolite, the kinetics and the factors affecting the adsorption efficiency. The maximum adsorption capacity reaches a value around 35 mg of Dy per gram of zeolite. The results from the adsorption isotherms and kinetic study revealed a good agreement with both Langmuir and Temkin models and pseudo-second-order kinetics. Furthermore, the thermodynamic analysis suggests that the adsorption of Dy onto the zeolite is a spontaneous and favorable process. The findings from this work could provide insights into the design and optimization of zeolite-based processes for REE recovery and recycling, contributing to the development of a more sustainable and circular economy.

Adsorptive recovery of rare earth elements from aqueous solution by citric acid crosslinked carboxymethylated cellulose nanofibril aerogel

Rare earth elements (REEs) have become crucial resources in the electric vehicle industry; however, their recycling remains challenging. In this study, we developed a carboxymethylated cellulose nanofibril aerogel crosslinked with citric acid (CMCNF-CA aerogel) through thermal treatment and employed it as an adsorbent for REE recovery. The CMCNF-CA aerogel possesses a substantial amount of free –COOH groups, resulting in a strong negative charge. This unique characteristic enables the aerogel to exhibit excellent adsorption capacities of 200 mg/g for lanthanum(La3+) and 170 mg/g for cerium(Ce3+). The findings from FTIR and XPS analyses provide insights into the adsorption mechanism. It is revealed that hydroxo-complexes, such as La-(OH)x and Ce-(OH)x, are adsorbed onto the CMCNF-CA aerogel through strong electrostatic interactions with the –COOH groups. This leads to the formation of metal ionic crosslinking. Remarkably, the CMCNF-CA aerogel maintains its high adsorption performance even after undergoing five consecutive adsorption-desorption cycles. Based on these results, we demonstrate that the CMCNF-CA aerogel is an efficient and reusable adsorbent for the sustainable recovery of La3+ and Ce3+ from aqueous solutions. This study offers promising prospects for addressing the challenges in the recycling of REEs, highlighting the potential of the CMCNF-CA aerogel as a practical solution in the field of REE recovery.

Rare Earth Elements Recovery from Primary and Secondary Resources Using Flotation: A Systematic Review

Rare earth minerals (REMs) contain rare earth elements (REEs) that are important in modern technologies due to their unique magnetic, phosphorescent, and catalytic properties. However, REMs are not only non-renewable resources but also non-uniformly distributed on the Earth’s crust, so the processing of REE-bearing secondary resources via recycling is one potential route to ensure the long-term sustainability of REE supply. Flotation—a method that separates materials based on differences in their surface wettability—is a process applied for both mineral processing and recycling of REEs, especially when the particles are fine and/or a high-purity product is required. In this review, studies about rare earth flotation from 2012 to 2021 were systematically reviewed using the PRISMA guideline. It was found that most REM flotation research works focused on finding better collectors and depressants while, for recycling, studies on advanced flotation techniques like froth flotation, ion flotation, solvent sublation, electroflotation, and adsorbing colloid flotation with an emphasis on the recovery of dissolved REEs from aqueous solutions dominated.

Highly efficient removal of rare earth elements by two-dimensional titanium carbide nanosheets as impacted via water chemistry.

The separation and recycling of rare earth elements (REEs) are very important owing to the high demand, limited resource, specific usages, and environmental issues. In this work, two-dimensional Ti3C2Tx MXene was introduced to remove REEs (Nd(III) and La(III)) from water, and its physicochemical properties were conducted by HRTEM, SEM-EDS, XRD, FTIR, and XPS. Various parameters, such as initial pH, REEs initial concentration, contact time, and temperature, were investigated by batch experiment, respectively. Furthermore, the adsorption kinetic and isotherm were examined to analyze the adsorption behavior and adsorption mechanism. Nd(III) and La(III) have a good affinity with Ti3C2Tx MXene surface functional groups (-F, -OH, and containing oxygen groups). The maximum adsorption capacities of Ti3C2Tx MXene for Nd(III) and La(III) were 229.85 mg/g and 175.83 mg/g at T = 333 K, respectively. The adsorption data of Nd(III) on Ti3C2Tx MXene fitted well with the Freundlich isotherms model and pseudo-second-order kinetic model. However, the best fitting for La(III) adsorption on Ti3C2Tx MXene was described by both pseudo-first-order and pseudo-second-order model. Thermodynamic study of Nd(III) and La(III) adsorption on Ti3C2Tx MXene showed that the reaction was a spontaneous and endothermic process. These results indicated Ti3C2Tx MXene had a great potential in extracting REEs from an aqueous solution.

Modeling phase equilibria and speciation in aqueous solutions of rare earth elements with hydroxide and organic ligands

A thermodynamic model has been developed for calculating speciation and phase equilibria in aqueous solutions of rare earth elements (REEs) with hydroxide, acetate, citrate, and oxalate anions. The computational framework is based on the Mixed-Solvent Electrolyte (MSE) framework, which has been previously used to establish a systematic treatment of binary and multicomponent systems containing REE sulfates and chlorides up to solid–liquid saturation at temperatures up to 300 °C. The model has been parametrized by performing a multi-property analysis of critically evaluated speciation and solubility data. For rare earth hydroxides, a comprehensive model has been developed for fourteen REEs (i.e., for yttrium and all lanthanides except promethium). The effect of the crystallinity of rare earth hydroxides on their solubility has been analyzed. Model parameters have been determined for two limiting cases, i.e., for crystalline and amorphous hydroxides, while recognizing that the hydroxides may span a range of degrees of crystallinity. For the organic ligands, the model has been established for neodymium with additional analysis for other selected REEs. The model accurately reproduces the effects of pH, temperature, and complexation with organic ligands on the behavior of rare earth elements in aqueous solutions. When coupled with previously developed models for inorganic rare earth salts, it provides a thermodynamic tool for the design and optimization of separation processes for the production and recycling of REEs and for predicting the properties of REEs in geological and biological settings.

Developing N,N,N’,N’-tetra (2-ethylhexyl) diglycolamide encapsulated polymeric beads as promising rare earth extracting agents

ABSTRACT The multi-faceted applications of rare earth elements (REE) in science and technology are not unknown. Scarcity in the primary sources of RE makes it necessary to explore different secondary sources available. Availability of REE in significant amount in spent NdFeB magnetic scrap makes the recycling of REE from this scrap, a lucrative option. In this work, synthetic solutions of 10 g/L (containing the rare earths Nd, Pr and Dy along with Fe) were equilibrated with the organic extractant N,N,N,’N’-tetra (2-ethylhexyl) diglycolamide (TEHDGA) encapsulated in polyethersulfone beads to study the extraction behavior of the REEs from nitric acid medium. Iron (Fe), the major component present in NdFeB scrap, poses the biggest challenge for rare earth extraction from the scraps. The TEHDGA impregnated polymeric beads were found to selectively extract the REEs, leaving Fe(III) in the feed solution. TEHDGA displayed higher selectivity towards the heavier rare earth Dy followed by Nd and Pr. The loading capacity of the beads was measured to be > 1700 ppm. The effect of different experimental parameters, such as contact time, solid-liquid ratio, TEHDGA concentration, feed acidity, were investigated. Contact time of 24 h, TEHDGA concentration of 0.75 M, solid-liquid ratio either 1:5 or 1:10 and feed acidity between 2 and 5 M have been found to suitable for quantitative extraction of REE particularly Dy(III). The recovery of the REEs from the loaded TEHDGA beads was > 90%. Furthermore, the experiment was carried out with higher quantity of beads and feed solution to study applicability of the same in bulk scale. A novel, easy and single-step separation of REE from Fe has been presented in this work.

Multiomics reveals Claroideoglomus etunicatum regulates plant hormone signal transduction, photosynthesis and La compartmentalization in maize to promote growth under La stress

Rare earth elements (REEs) have been widely used in traditional and high-tech fields, and high doses of REEs are considered a risk to the ecosystem. Although the influence of arbuscular mycorrhizal fungi (AMF) in promoting host resistance to heavy metal (HM) stress has been well documented, the molecular mechanism by which AMF symbiosis enhances plant tolerance to REEs is still unclear. A pot experiment was conducted to investigate the molecular mechanism by which the AMF Claroideoglomus etunicatum promotes maize (Zea mays) seedling tolerance to lanthanum (La) stress (100 mg·kg−1 La). C. etunicatum symbiosis significantly improved maize seedling growth, P and La uptake and photosynthesis. Transcriptome, proteome, and metabolome analyses performed alone and together revealed that differentially expressed genes (DEGs) related to auxin /indole-3-acetic acid (AUX/IAA) and the DEGs and differentially expressed proteins (DEPs) related to ATP-binding cassette (ABC) transporters, natural resistance-associated macrophage proteins (Nramp6), vacuoles and vesicles were upregulated. In contrast, photosynthesis-related DEGs and DEPs were downregulated, and 1-phosphatidyl-1D-myo-inositol 3-phosphate (PI(3)P) was more abundant under C. etunicatum symbiosis. C. etunicatum symbiosis can promote plant growth by increasing P uptake, regulating plant hormone signal transduction, photosynthesis and glycerophospholipid metabolism pathways and enhancing La transport and compartmentalization in vacuoles and vesicles. The results provide new insights into the promotion of plant REE tolerance by AMF symbiosis and the possibility of utilizing AMF–maize interactions in REE phytoremediation and recycling.

Rare earth metals detection and recognition based on laser induced breakdown spectroscopy and machine learning.

The rapid detection and identification of the electronic waste (e-waste) containing rare earth (RE) elements is of great significance for the recycling of RE elements. However, the analysis of these materials is extremely challenging due to extreme similarities in appearance or chemical composition. In this research, a new system based on laser induced breakdown spectroscopy (LIBS) and machine learning algorithms is developed for identifying and classifying e-waste of rare-earth phosphors (REPs). Three different kinds of phosphors are selected and the spectra is monitored using this new developed system. The analysis of phosphor spectra shows that there are Gd, Yd, and Y RE element spectra in the phosphor. The results also verify that LIBS could be used to detect RE elements. An unsupervised learning method, principal component analysis (PCA), is used to distinguish the three phosphors and training data set is stored for further identification. Additionally, a supervised learning method, backpropagation artificial neural network (BP-ANN) algorithm is used to establish a neural network model to identify phosphors. The result show that the final phosphor recognition rate reaches 99.9%. The innovative system based on LIBS and machine learning (ML) has the potential to improve rapid in situ detection of RE elements for the classification of e-waste.

Cyclic raises cash for rare earth recycling

Cyclic Materials has raised $27 million in series A financing to advance its technology for recycling of rare earth elements. Rare earths are used to make magnets required for electric vehicle motors, wind turbines, and electronics. Most rare earth materials are processed in China, and Cyclic says its recycling process would provide an alternative source, thus making supply chains more secure. The company also argues that recycling rare earths has a lower environmental impact than mining.

Cyclic raises $27 million for rare earth recycling

Cyclic raises $27 million for rare earth recycling

Phase Relations in the CaO-Nd2O3-Al2O3 System in Application for Rare Earth Recycling

Phase relations in the CaO-Al2O3-Nd2O3 system were investigated in the temperature range between 1330°C and 1600°C using equilibration technique followed by characterization using x-ray diffraction and scanning electron microscopy combined with energy-dispersive x-ray spectroscopy (SEM/EDX). Melting relations were investigated using differential thermal analysis followed by microstructure study using SEM/EDX. It was found that CaNdAlO4 (τ1) compound melted congruently at 1808°C, while CaNdAl3O7 (τ2) compound melted incongruently at 1766°C. The sample in the stability fields adjacent to lowest eutectic in the CaO-Al2O3 system (CaAl2O4 + Ca3Al2O6) and τ2 as well as samples in the stability field τ2 + CaAl2O4 + CaAl4O7 and τ1 + τ2 + Ca3Al2O6 were completely melted at 1600°C. The Ca12Al14O33 phase considered as not stable in anhydrous atmosphere was found instead of Ca3Al2O6 phase after heat treatment at 1330°C. After melting Ca12Al14O33 formed glass. The obtained results are important for selection of conditions for process of rare earth recycling from waste permanent NdFeB magnets.