Selective Extraction of Rare Earth Elements from NdFeB Scrap by Molten Chlorides

Abstract

With rapid growth in the use of NdFeB magnets and growing concerns for environmental protection as well as conservation of rare earths (REs), the recycling of NdFeB magnet scrap is becoming a hot issue for current society. In this study, it is demonstrated that the rare earths in a NdFeB magnet can be selectively extracted using molten MgCl2–KCl salts at temperatures of 600–1200 °C. After crushing to granules, the scrap was subjected to molten chlorides in a dry argon atmosphere. The reaction process between NdFeB scrap and molten MgCl2–KCl was directly observed using a high-temperature contact angle measuring instrument to clarify the phenomena that occur when rare earth chlorides are formed in situ. Furthermore, the effects of reaction temperature, holding time, and mass ratio of MgCl2/NdFeB were investigated to transform REs in the scrap to RECl3 as completely as possible. The reaction products were examined with the necessary analytical techniques including SEM, EDS, XRD, and ICP. The overall extraction efficiency for REs was found to be more than 90% under the optimum operating conditions. The obtained RECl3 in the molten MgCl2–KCl can be processed with molten salt electrolysis for the direct production of Mg–Nd alloy.