Processing of Grinding Slurries Arising from NdFeB Magnet Production

Kruse, Stephanie; Raulf, Karoline; Trentmann, Anna; Pretz, Thomas; Friedrich, Bernd

doi:10.1002/cite.201500070

Cited by 11 publications

(19 citation statements)

References 8 publications

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“…Using the Rietveld refinement method, it was possible to identify that both samples are mainly formed by the Nd 2 Fe 14 B phase. This is consistent with the results reported in the literature, ,,, which indicate that the sludge samples studied are mainly formed by the Nd 2 Fe 14 B phase. Other phases such as Nd 2 O 3 , Fe 2 O 3 , and α-Fe have been found in other studies; ,, however, they have not been detected in the samples studied in this work.…”

Section: Resultssupporting

confidence: 93%

“…The existing literature on the recycling of RE–Fe–B machining wastes focuses on the processes used, while the properties of the feedstock are hardly addressed. ,,− ,− Particle morphology, chemical composition, and phases present in machining wastes are often addressed and, in some cases, particle size analysis is also shown. ,,− , …”

Section: Introductionmentioning

confidence: 99%

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Structural and Magnetic Characterization of Nd–Pr–Fe–B Sintered Magnet Machining Wastes

et al. 2023

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Nd–Pr–Fe–B sintered magnets are considered important for emerging technologies. They are fundamental to the energy matrix transition, such as electric and hybrid vehicles and wind turbines. The production of these magnets generates tons of residues in the machining process step. Since China dominates the rare-earth (RE) market, leading to supply shortages, processing wastes are a promising alternative for recycling or reusing RE materials. Due to the amount generated and the chemical composition, containing up to 30 wt % of critical rare-earth elements, the studies of RE magnets are expanding in the current circular economy scenario. In this work, Nd–Pr–Fe–B machining wastes from two different machining processes (diamond cutting and grinding) were characterized by X-ray diffraction, Mössbauer spectroscopy, vibrating sample magnetometer with first-order-reversal-curves, scanning electron microscopy, X-ray fluorescence, elemental analysis, and X-ray photoelectron spectroscopy. The results showed that the degradation of the phases in both wastes is relatively strong. The phases of the magnets are decomposed into oxides, hydroxides, and hydrated oxides such as Nd(OH)3, ferrihydrite, and metallic iron. In addition, the machining process provokes a change in the iron vicinity of the Nd2Fe14B phase. The presence of impurities and the wide dispersion of particle sizes resulted in low magnetic properties and affected the magnetization behavior of the machining waste. Using different characterization techniques, it was found that the oxides formed during the machining processes are located on the surfaces of the particles, while the center consists of a nondegraded Nd2Fe14B phase. It was also found that the Nd–Pr–Fe–B wastes have similarities, indicating that it is possible to mix wastes from different machining processes before recycling. The complete characterization of the Nd–Pr–Fe–B machining residues indicated that different reuse and recycling strategies can be evaluated to improve the efficiency of reusing these machining wastes as secondary sources.

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Section: Resultssupporting

confidence: 93%

Section: Introductionmentioning

confidence: 99%

Structural and Magnetic Characterization of Nd–Pr–Fe–B Sintered Magnet Machining Wastes

et al. 2023

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“…[7][8][9] There have been plenty of studies on the recovery of REEs using pyrometallurgy and hydrometallurgy. [10][11][12][13][14][15][16][17][18] The widely preferred technique for recovering REEs from waste materials is hydrometallurgy. Hydrometallurgical processes can produce pure products from lower grade and complex streams.…”

Section: Introductionmentioning

confidence: 99%

Recycling of NdFeB magnets employing oxidation, selective leaching, and iron precipitation in an autoclave

et al. 2023

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“…This combined environmentally friendly process for recovery of nanosized powder mixture of Nd 2 O 3 and Pr 2 O 3 from spent magnets and re-use of nitric acid shall be reduced considered in scale up conditions. The final winning of the mixture of metallic Nd and Pr will be ensured using molten salt electrolysis [88][89][90].…”

Section: Recovery Of Ree From Waste Of Electrical and Electronic Equipment (Weee Or E-waste)mentioning

confidence: 99%

“…1 Kruse et al [90] proposed a pyrometallurgical treatment of the grinding slurries aiming recovering REE. The possibility of recycling the contained REE, which account for up to 30 wt.…”

Section: Recovery Of Ree From Waste Of Electrical and Electronic Equipment (Weee Or E-waste)mentioning

confidence: 99%

Advances in Understanding of the Application of Unit Operations in Metallurgy of Rare Earth Elements

Stopić

Friedrich

2021

Metals

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Unit operations (UO) are mostly used in non-ferrous extractive metallurgy (NFEM) and usually separated into three categories: (1) hydrometallurgy (leaching under atmospheric and high pressure conditions, mixing of solution with gas and mechanical parts, neutralization of solution, precipitation and cementation of metals from solution aiming purification, and compound productions during crystallization), (2) pyrometallurgy (roasting, smelting, refining), and (3) electrometallurgy (aqueous electrolysis and molten salt electrolysis). The high demand for critical metals, such as rare earth elements (REE), indium, scandium, and gallium raises the need for an advance in understanding of the UO in NFEM. The aimed metal is first transferred from ores and concentrates to a solution using a selective dissolution (leaching or dry digestion) under an atmospheric pressure below 1 bar at 100 °C in an agitating glass reactor and under a high pressure (40–50 bar) at high temperatures (below 270 °C) in an autoclave and tubular reactor. The purification of the obtained solution was performed using neutralization agents such as sodium hydroxide and calcium carbonate or more selective precipitation agents such as sodium carbonate and oxalic acid. The separation of metals is possible using liquid (water solution)/liquid (organic phase) extraction (solvent extraction (SX) in mixer-settler) and solid-liquid filtration in chamber filter-press under pressure until 5 bar. Crystallization is the process by which a metallic compound is converted from a liquid into a crystalline state via a supersaturated solution. The final step is metal production using different methods (aqueous electrolysis for basic metals such as copper, zinc, silver, and molten salt electrolysis for REE and aluminum). Advanced processes, such as ultrasonic spray pyrolysis, microwave assisted leaching, and can be combined with reduction processes in order to produce metallic powders. Some preparation for the leaching process is performed via a roasting process in a rotary furnace, where the sulfidic ore was first oxidized in an oxidic form which is a suitable for the metal transfer to water solution. UO in extractive metallurgy of REE can be successfully used not only for the metal wining from primary materials, but also for its recovery from secondary materials.

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Processing of Grinding Slurries Arising from NdFeB Magnet Production

Cited by 11 publications

References 8 publications

Structural and Magnetic Characterization of Nd–Pr–Fe–B Sintered Magnet Machining Wastes

Structural and Magnetic Characterization of Nd–Pr–Fe–B Sintered Magnet Machining Wastes

Recycling of NdFeB magnets employing oxidation, selective leaching, and iron precipitation in an autoclave

Advances in Understanding of the Application of Unit Operations in Metallurgy of Rare Earth Elements

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