(381q) Selective Separation of Rare Earth Elements from NdFeB Powders By Caustic Digestion

As the demand of NdFeB magnets increases, an abundance of waste magnets has been gradually released from the end-of-life devices and systems. Therefore, the recycling of permanent magnet has attracted much attention and several methods based on pyro/hydro-metallurgy have been tried and developed for recovering valuable metals from magnet. It is well known that NdFeB powders from permanent magnets are liable to be oxidized, so, the direct application of waste magnets is limited to use the production process of new and high-performance magnet. Therefore, recovery of pure REEs materials from waste magnet via hydrometallurgical route have been much studied and developed. However, the problems associated with the hydrometallurgical process (use of large amounts of strong acid and discharging of large amounts of acidic waste solution containing ferrous/ferric ions) has yet to be unsolved. In previous study, the selective separation of rare earth elements from non-oxidized magnets powders was reported to be possible through the caustic digestion and oxidation roasting of NdFeB metal powder. In this study, the caustic digestion and oxidation roasting of NdFeB metal powder was investigated for the recycling of waste NdFeB magnet powders obtained by Hydrogen Decrepitation (HD) process. The caustic digestion and oxidation roasting of NdFeB metal powder produced Nd₂O₃ and Fe₂O₃ except NdFeO₃. The selective separation of rare earth element from iron had been achieved by the dilute acid leaching of Nd₂O₃ and Fe₂O₃, The leaching yield of rare earth element was more than 95%, and that of iron was negligible.