On the pre-treatment for recycling spent NdFeB permanent magnets: from disassembling, characterisation to de-coating

• Published in: Sustainable Materials and Technologies 2024-09, Vol.41, p.e01041, Article e01041
• Main Authors: Couto, Camila Pucci, van de Ven, Johannes J.M.M., Yang, Yongxiang, Abrahami, Shoshan T.
• Format: Article
• Language: English
• Subjects: Critical-raw materials; De-coating; NdFeB permanent magnets; Rare-earth elements; Recycling
• ISSN: 2214-9937
• DOI: 10.1016/j.susmat.2024.e01041

An evaluation of neodymium‑iron‑boron permanent magnets (NdFeB PMs) from different end-of-life products, as a secondary resource of rare-earth elements (REEs), is presented. De-coating of PM was investigate as pre-treatment to facilitate efficient direct magnet recycling. Thus, critical aspects from disassembling to the de-coating of the magnets were addressed. A challenge for the de-coating process is that the magnets have different sizes, weights, and their coating compositions are not known beforehand. It was shown that ammonia-based solutions was thermodynamically suitable to dissolve nickel and zinc coatings selectively, while keeping the bulk magnet stable. Nevertheless, the dissolution of Zn was much faster than the Ni one, and more efficient. •Various magnets from different EoL products were disassembled and characterised•The most popular coatings found in NdFeB PMs were Ni and Zn•Ammonia-based lixiviants selectively dissolve Ni and Zn coatings•The bulk magnet was stable in ammonia-based solutions•NH4Cl in ammonia improves the dissolution of Ni and Zn coatings