Separation and Recovery of Rare Earth Metals by Molten Salt Electrolysis using Alloy Diaphragm

Oishi, Tadashi; Konishi, Hisatoshi; Nohira, Toshiyuki; Tanaka, Mikiya; Usui, Tateo

doi:10.1252/kakoronbunshu.36.299

Cited by 57 publications

(61 citation statements)

References 4 publications

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“…The addition of Dy is necessary to improve the thermal stability of Nd-Fe-B magnets. However, there is the concern about a Molten salt We proposed a new separation and recovery process for RE metals from scraps using molten salt and an alloy diaphragm (20,21). The new process is based on our previously discovered phenomena, i.e., "electrochemical implantation" and "electrochemical displantation" (1).…”

Section: Introductionmentioning

confidence: 99%

(Keynote) Separation of Dy and Nd (La) Using Molten Salt and an Alloy Diaphragm

Konishi

Ono

Oishi³

2013

ECS Trans.

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Cyclic voltammetry was conducted using a Ni electrode in molten LiCl-KCl-RECl 3 (RE=Dy, Nd) systems at 723 K. In cathodic scan, a cathodic current was observed from 1.00 V (vs. Li + /Li) due to the formation of Dy-Ni alloys in a molten LiCl-KCl-DyCl 3 system. In contrast, a cathodic current was observed from 0.60 V due to the formation of Nd-Ni alloys in a molten LiCl-KCl-NdCl 3 system. On the basis of these results, an alloy sample was prepared by potentiostatic electrolysis at 0.65 V for 1 h using a Ni plate cathode in a molten LiCl-KCl-DyCl 3 -NdCl 3 system. The mass ratio of Dy/Nd in the alloy sample was found to be 72 by ICP-AES. Another investigation was conducted in a molten LiCl-KCl-DyCl 3 -LaCl 3 system, with and without FeCl 2 addition. Regardless of the presence of FeCl 2 , DyNi 2 was selectively formed on a Ni plate cathode at 0.55 V.

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Section: Introductionmentioning

confidence: 99%

(Keynote) Separation of Dy and Nd (La) Using Molten Salt and an Alloy Diaphragm

Konishi

Ono

Oishi³

2013

ECS Trans.

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“…4,[6][7][8][9][10][11] According to our previous studies, a specific RE element can be alloyed and de-alloyed rapidly with iron-group (IG) * Electrochemistry Society Active Member z E-mail: yasuda.kouji.3v@kyoto-u.ac.jp; nohira@energy.kyoto-u.ac.jp metals in molten salts by using electrochemical methods. 12 In the proposed process, Nd, Dy, and Pr are separated because of differences in both the formation potentials and formation rates of the RE-IG alloys used as the diaphragm.…”

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confidence: 99%

Electrochemical Formation of Pr–Ni Alloys in LiF–CaF₂–PrF₃and NaCl–KCl–PrCl₃Melts

Yasuda

Kondo

Hagiwara

2014

J. Electrochem. Soc.

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For the establishment of a process for the electrochemical recovery of rare earth elements from used magnet scraps, the electrochemical formation of Pr-Ni alloys in molten LiF-CaF 2 -PrF 3 and NaCl-KCl-PrCl 3 salts at 1123 K and 973 K, respectively, was investigated.Cyclic voltammetry and open-circuit potentiometry indicated the formation of several phases of Pr-Ni alloys. Alloy samples were prepared by one-or two-step potentiostatic electrolysis using a Ni plate electrode at various potentials. Scanning electron microscopy observations and X-ray diffraction measurements confirmed the formation of PrNi 2 , PrNi 3 , Pr 2 Ni 7 , and PrNi 5 . The formation potential for each Pr-Ni alloy phase was determined from experimental results. In addition, the optimum electrolysis conditions for the separation of Nd, Dy, and Pr are discussed.Rare earth (RE) metals have several superior characters such as electric, magnetic, and fluorescence properties and are therefore indispensable as industrial materials throughout the world. Among the many applications of RE metals, the use of neodymium-ironboron (Nd-Fe-B) magnets-the so-called neodymium permanent magnets-has been remarkably increasing recently. Neodymium permanent magnets composed of a Nd 2 Fe 14 B main phase have several advantages such as superior magnetic properties and high mechanical strength, and are used for voice coil motors in hard disk drives (HDDs), magnetic resonance imaging (MRI), speakers/vibrators in cell phones, and motors in electric vehicles (EVs) and hybrid electric vehicles (HEVs). Since praseodymium (Pr) and Nd have similar chemical properties, they are found in nature in the same ores and their separation is difficult. Thus, in some applications including permanent magnets, a Nd-Pr alloy called didymium (Di) is sometimes utilized. On the other hand, Nd-Fe-B magnets have the drawback of a relatively low Curie temperature of ∼583 K. In order to maintain its superior coercive force even at high temperatures (above 473 K), where high-performance motors in EVs and HEVs operate, dysprosium (Dy) is necessary as an additive.One of the concerns pertaining to RE magnets is the uneven distribution of RE resources: in 2011, China had 50% of the proven RE reserves and produced over 97% of the global RE supply. 1 In 2010-2012, the price of REs increased sharply, causing supply problems for the magnets. While the present RE production capacity satisfies the demand and their price has lowered, there remains the potential for RE shortage in the future.On the basis of these supply circumstances, it can be concluded that the recycling or waste management of Nd-Fe-B magnet scraps is currently an urgent task. The conventional wet processes for RE recycling from Nd-Fe-B magnet scraps have several disadvantages such as their multistep and complicated processes, high environmental loads, and large energy consumption. As new recycling methods, pyrometallurgical processes such as chemical vapor transport, 2 selective reduction, 3 molten salt electrolysis, 4 and ionic liquid e...

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“…The application was further developed by Yasuda et al [54] to prepare RE-Ni alloy from magnet scrap using molten NaCl-KCl-RECl 3 as electrolyte. Konishi et al [83,84] performed anodic potentiostatic electrolysis at 1.70 and 2.20 V for 12 h using Nd-Fe-B magnet as electrodes. The RE ions were reduced on the anode compartment side of the alloy diaphragm.…”

Section: Electrolysis Using Molten Salt and Ionic Liquidsmentioning

confidence: 99%

Review of High-Temperature Recovery of Rare Earth (Nd/Dy) from Magnet Waste

Firdaus

Rhamdhani

Durandet

et al. 2016

J. Sustain. Metall.

108

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Rare-earth metals, particularly neodymium, dysprosium, and praseodymium are becoming increasingly important in the transition to a green economy due to their essential role in permanent magnet applications such as in electric motors and generators. With the increasingly limited rare-earth supply and complexity of processing Nd, Dy, and Pr from primary ores, recycling of rare-earth based magnets has become a necessary option to manage supply and demand. Depending on the form of the starting material (sludge or scrap), there are different routes that can be used to recover neodymium from secondary sources, ranging from hydrometallurgical (based on its primary production process), electrochemical to pyrometallurgical. Pyrometallurgical routes provide solution in cases where water is scarce and generation of waste is to be limited. This paper presents a systematic review of previous studies on the high-temperature (pyrometallurgical) recovery of rare earths from magnets. The features and conditions at which the recycling processes had been studied are mapped and evaluated technically. The review also highlights the reaction mechanisms, behaviors of the rare-earth elements, and the formation of intermediate compounds in high-temperature recycling processes. Recommendations for further scientific research to enable the development of recovery of the rare-earth and magnet recycling are also presented.

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Separation and Recovery of Rare Earth Metals by Molten Salt Electrolysis using Alloy Diaphragm

Cited by 57 publications

References 4 publications

(Keynote) Separation of Dy and Nd (La) Using Molten Salt and an Alloy Diaphragm

(Keynote) Separation of Dy and Nd (La) Using Molten Salt and an Alloy Diaphragm

Electrochemical Formation of Pr–Ni Alloys in LiF–CaF₂–PrF₃and NaCl–KCl–PrCl₃Melts

Review of High-Temperature Recovery of Rare Earth (Nd/Dy) from Magnet Waste

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Separation and Recovery of Rare Earth Metals by Molten Salt Electrolysis using Alloy Diaphragm

Cited by 57 publications

References 4 publications

(Keynote) Separation of Dy and Nd (La) Using Molten Salt and an Alloy Diaphragm

(Keynote) Separation of Dy and Nd (La) Using Molten Salt and an Alloy Diaphragm

Electrochemical Formation of Pr–Ni Alloys in LiF–CaF2–PrF3and NaCl–KCl–PrCl3Melts

Review of High-Temperature Recovery of Rare Earth (Nd/Dy) from Magnet Waste

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Electrochemical Formation of Pr–Ni Alloys in LiF–CaF₂–PrF₃and NaCl–KCl–PrCl₃Melts