Rare-earth elements recovery from post-consumer hard-disc drives

Abstract

The recovery of neodymium from post-consumer products is gaining significant interest. To study the recycling feasibility of neodymium in end-of-life (EOL) computer hard disc drives (HDDs), NdFeB magnets were collected using a steel grate during commercial shredding, followed by thermal demagnetisation, grinding and screening to yield an upgraded scrap. Two metallurgical extraction routes were investigated. The first is a high temperature molten slag extraction followed by H₂SO₄ leaching at room temperature. Both CaO–SiO₂–Al₂O₃ and CaO–CaF₂ slag systems were tested with more than 99% rare earths recovery, but with incomplete leaching. In the second route, the upgraded scrap was directly leached to dissolve 97% rare earth content. In both cases, 98% of the rare earths in the leach solution were subsequently converted into a high purity (98·4%) rare earths double salt (NaNd(SO₄)₂·H₂O) that can be converted to either RF₃ or R₂O₃, the two common raw materials in the production of rare earth metals.