Recovery of Rare Earth Elements through Spent NdFeB Magnet Oxidation (First Part)

Srecko Stopic*, Buse Polat, Hanwen Chung, Elif Emil-Kaya, Slavko Smiljanić, Sebahattin Gürmen, Bernd Friedrich

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

12 Citations (Scopus)

Abstract

Due to their remarkable magnetic properties, such as a high maximum energy product, high remanence, and high coercivity, NdFeB magnets are used in a variety of technological applications. Because of their very limited recycling, high numbers of spent NdFeB magnets are widely available in the market. In addition to China’s monopoly on the supply of most rare earth elements, there is a need for the recovery of these critical metals, as their high import price poses an economic and environmental challenge for manufacturers. This paper proposes a pyrometallurgical recycling method for end-of-life NdFeB magnets by oxidizing them in air as first required step. The main goal of this method is to oxidize rare earth elements from NdFeB magnets in order to prepare them for the carbothermic reduction. The experimental conditions, such as the oxidation temperature and time, were studied in order to establish the phase transformation during oxidation using the Factsage Database and experimental conditions. Our thermogravimetric analysis TGA analysis revealed an increased sample mass by 35% between room temperature and 1100 °C, which is very close to the total calculated theoretical value of oxygen (36.8% for all elements, and only 3.6% for rare earth elements REE), confirming the complete oxidation of the material. The obtained quantitative analysis of the oxidation product, in (%), demonstrated values of 53.41 Fe2O3, 10.37 Fe3O4; 16.45 NdFeO3; 0.45 Nd2O3, 1.28 Dy2O3, 1.07 Pr2O3, and 5.22 α-Fe.

Original languageEnglish
Article number1464
JournalMetals
Volume12
Issue number9
DOIs
Publication statusPublished - Sept 2022

Bibliographical note

Publisher Copyright:
© 2022 by the authors.

Funding

This research was funded by the Federal Ministry for Economic Affairs and Climate Action, grant number 273 EN. The APC was funded by the project “sustainable recovery of rare earth elements (Nd, Pr, Dy) from spent magnets”.

FundersFunder number
Federal Ministry for Economic Affairs and Climate Action273 EN

    Keywords

    • magnets
    • oxidation
    • rare earth elements
    • recycling

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