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

Abstract

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.