One-step recovery of REE oxalates in electro-leaching of spent NdFeB magnets

Makarova, Irina; Ryl, Jacek; Sun, Zhi; Курило, И. И.; Górnicka, Karolina; Laatikainen, Markku; Repo, Eveliina

doi:10.1016/j.seppur.2020.117362

Cited by 27 publications

(4 citation statements)

References 42 publications

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“…The primary components, with Fe 2p 3/2 located at 710.8 and 712.9 eV, respectively, should be ascribed to Fe 3? species like in oxides [30,31]. Such compounds are always highspin, leading to complex multiplet split spectra.…”

Section: Glass Formation and Reaction Of Aluminum Crucible With The Meltmentioning

confidence: 99%

Mechanism of hopping conduction in Be–Fe–Al–Te–O semiconducting glasses and glass–ceramics

et al. 2022

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Electrical properties of beryllium-alumino-tellurite glasses and glass–ceramics doped with iron ions were studied using impedance spectroscopy. The conductivity was measured over a wide frequency range from 10 mHz to 1 MHz and the temperature range from 213 to 473 K. The D.C. conductivity values showed a correlation with the Fe-ion concentration and ratio of iron ions on different valence states in the samples. On the basis of Jonscher universal dielectric response the temperature dependence of conductivity parameters were determined and compared to theoretical models collected by Elliott. In glasses, the conduction process was found to be due to the overlap polaron tunneling while in glass–ceramics the quantum mechanical tunneling between semiconducting crystallites of iron oxides is proposed. The D.C. conductivity was found not to follow Arrhenius relation. The Schnakenberg model was used to analyze the conductivity behavior and the polaron hopping energy and disorder energy were estimated. Additionally, the correlation between alumina dissolution and basicity of the melts was observed.

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Section: Glass Formation and Reaction Of Aluminum Crucible With The Meltmentioning

confidence: 99%

Mechanism of hopping conduction in Be–Fe–Al–Te–O semiconducting glasses and glass–ceramics

et al. 2022

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“…A rare earth oxalate deposit of 93% was obtained simultaneously with electro-leaching of magnet in a bath mixture of sulfuric and oxalic acid. 32 However, the purity of the deposit drops over time as iron also co-deposits. Consequently, ensuring purer rare earth oxalate will result in incomplete magnet dissolution.…”

Section: Introductionmentioning

confidence: 99%

“…The simultaneous oxidation and reduction of iron in undivided cells raises energy consumption and thus makes it difficult to implement at a larger scale. A rare earth oxalate deposit of 93% was obtained simultaneously with electro-leaching of magnet in a bath mixture of sulfuric and oxalic acid . However, the purity of the deposit drops over time as iron also co-deposits.…”

Section: Introductionmentioning

confidence: 99%

A Novel Electrochemical Process for Recovery of Rare Earth Elements and Iron from Neodymium–Iron–Boron Based Magnets

Haque,

Alvarez-Pugliese,

Botte

2024

ACS Sustainable Resour. Manage.

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A novel low-temperature electrochemical method for rare earth elements (REEs) recovery from spent permanent magnets was investigated at bench scale. First, magnets were completely dissolved in a 2 g sulfuric acid/g magnet powder solution at room temperature. Then, the iron present in the leachate was either oxidized or reduced electrochemically. After that, REEs were separated as double salt precipitates by the addition of sodium sulfate or sodium hydroxide. A sodium sulfate quantity of 5 times the stoichiometric mass amount proved to be adequate for achieving recovery rates of 90−99% for neodymium, praseodymium, and terbium in the acid leachate, while ensuring no iron coprecipitation. Iron speciation (either fully oxidized or fully reduced) was demonstrated to have no apparent effect on REEs recovery. However, 2−7% iron coprecipitation was observed for acid leachate containing fully reduced iron. Finally, iron, the element of higher weight fraction in magnets, was recovered (77.32% in 20 h) in its useful metallic form by a divided electrowinning process at a moderate temperature (70 °C). The purity of the electrodeposited iron layer was determined to be 95.20 ± 3.57%. The novelty of the proposed environmentally friendly method is the recovery of iron in metallic electrolytic form and REEs in sulfate form, avoiding high temperature pyrometallurgical methods (roasting) or the use of additional chemical oxidizers.

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“…Hydrometallurgical and pyro-hydrometallurgical processes are common methods used to recover REEs from NdFeB wastes, , such as the use of bifunctional ionic liquids as extractants; oxidation roasting combined with hydrochloric acid leaching; nitration, calcination, and water leaching; mechanochemical method combined with ferric sulfate leaching; and roasting and HCl leaching . Electrochemical–hydrometallurgical processes have also been used, such as selective extraction with HCl after electrolysis pretreatment, selective electrochemical extraction with oxalic acid and NaCl, electrolysis and selective precipitation, electrochemical leaching with sulfuric and oxalic acids, and precipitation of REEs in hydrofluoric acid and recycling of Fe by electrodeposition . Chlorination and fluorination processes previously used include chlorination of REEs by Cl 2 gas, electrolysis in molten LiF–CaF 2 , and chlorination of REEs by the mixture of MgCl 2 and KCl or molten MgCl 2 , and VIM-HMS process (a combination of vacuum induction melting, hydrolysis, and magnetic separation) .…”

Section: Introductionmentioning

confidence: 99%

Novel Approach for the Simultaneous Recovery of Nd from Nd₂O₃-Containing Slag and the Preparation of High-Purity Si

Lei

et al. 2021

ACS Sustainable Chem. Eng.

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The extraction of rare earth elements (REEs) from rare earth oxide slag is a major challenge of recycling REEs from REE-containing wastes using pyrometallurgical approaches, especially the recycling of Nd from spent NdFeB permanent magnets. In this study, a novel and effective approach is proposed for extracting Nd from Nd 2 O 3 -containing slag. First, low-purity Si (99.2%) was used as a reductant to extract Nd from Nd 2 O 3containing slag to prepare a bulk Si−Nd alloy. The bulk Si−Nd alloy represents one of the final products and achieves the purpose of Nd recycling because of its wide applications; alternatively, the bulk Si−Nd alloy can be further separated into Si powder and Ndcontaining HCl solution by HCl acid leaching. Thereafter, three methods can be used to recover Nd from the Nd-containing HCl solution: (1) NH 3 •H 2 O can be used to precipitate Nd 3+ as NdOCl hydrate sediment, which is roasted to obtain high-purity NdOCl (99.0%); (2) HF can be used to precipitate Nd 3+ as NdF 3 (97.0%); or (3) NdCl 3 •6H 2 O (98.1%) can be obtained after completely distilling the Nd-containing HCl solution. This new technology not only permits the recovery of Nd from the Nd 2 O 3 -containing slag but also increases the purity of Si from 99.2 to 99.997%.

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One-step recovery of REE oxalates in electro-leaching of spent NdFeB magnets

Cited by 27 publications

References 42 publications

Mechanism of hopping conduction in Be–Fe–Al–Te–O semiconducting glasses and glass–ceramics

Mechanism of hopping conduction in Be–Fe–Al–Te–O semiconducting glasses and glass–ceramics

A Novel Electrochemical Process for Recovery of Rare Earth Elements and Iron from Neodymium–Iron–Boron Based Magnets

Novel Approach for the Simultaneous Recovery of Nd from Nd₂O₃-Containing Slag and the Preparation of High-Purity Si

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One-step recovery of REE oxalates in electro-leaching of spent NdFeB magnets

Cited by 27 publications

References 42 publications

Mechanism of hopping conduction in Be–Fe–Al–Te–O semiconducting glasses and glass–ceramics

Mechanism of hopping conduction in Be–Fe–Al–Te–O semiconducting glasses and glass–ceramics

A Novel Electrochemical Process for Recovery of Rare Earth Elements and Iron from Neodymium–Iron–Boron Based Magnets

Novel Approach for the Simultaneous Recovery of Nd from Nd2O3-Containing Slag and the Preparation of High-Purity Si

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Product

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Novel Approach for the Simultaneous Recovery of Nd from Nd₂O₃-Containing Slag and the Preparation of High-Purity Si