A1 Journal article (refereed)
Acetic acid leaching of neodymium magnets and iron separation by simple oxidative precipitation (2022)

Niskanen, J., Lahtinen, M., & Perämäki, S. (2022). Acetic acid leaching of neodymium magnets and iron separation by simple oxidative precipitation. Cleaner Engineering and Technology, 10, Article 100544. https://doi.org/10.1016/j.clet.2022.100544

JYU authors or editors

Publication details

All authors or editors: Niskanen, Joni; Lahtinen, Manu; Perämäki, Siiri

Journal or series: Cleaner Engineering and Technology

eISSN: 2666-7908

Publication year: 2022

Volume: 10

Article number: 100544

Publisher: Elsevier BV

Publication country: United Kingdom

Publication language: English

DOI: https://doi.org/10.1016/j.clet.2022.100544

Publication open access: Openly available

Publication channel open access: Open Access channel

Publication is parallel published (JYX): https://jyx.jyu.fi/handle/123456789/82803

Abstract

Neodymium-iron-boron (NdFeB) has become the most prominent permanent magnet alloy, with a wide variety of applications and an ever-increasing demand. Their recycling is important for securing the supply of critical raw materials used in their manufacturing. The use of organic acids such as acetic acid has been of recent interest for the recycling of waste NdFeB magnets. Despite achieving good leaching efficiencies, the published literature has not properly investigated the effects of key factors influencing the acetic acid leaching process and their respective interactions, which has lead to conflicting findings as to what conditions are optimal. The present work goes to show that no such optimum actually exists by taking a look at the major factors (concentration, solid-to-liquid ratio, time and temperature) and their interactions. The results show that leaching efficiencies >95% and even up to 100% can be achieved using a variety of different conditions showing that the leaching reaction is quite flexible, which is helpful for a potential upscaling of the process. Separation of the leached elements presents another problem in NdFeB magnet processing. As a novel application, this work investigated iron separation from the acetic acid leachate by the means of simple and inexpensive aeration. It was found that up to 99% of iron could be precipitated as FeO(OH) (goethite) within 2 h at pH 5 and 80 °C, while only minor neodymium co-precipitation was observed (5%). Separation of iron from the leachate can help obtain purer REE products in further processing.

Keywords: metals; rare earth metals; recycling; reuse; acetic acid

Free keywords: spent NdFeB magnet; rare earth element: REE; critical raw material; acetic acid leaching; iron precipitation

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Ministry reporting: Yes

VIRTA submission year: 2022

JUFO rating: 1