Production of rare earth element oxide powders by solution combustion: a new approach for recycling of NdFeB magnets

Abstract

NdFeB magnets are employed in various technological applications due to their outstanding magnetic properties, such as high maximum energy product, high remanence and high coercivity. Production of NdFeB has gathered more interest, therefore the demand for rare earth elements (REEs) has continuously increased. The recovery of REEs has become essential to satisfy this demand in recent years. In the present study, a promising flowsheet is proposed for REEs recovery from NdFeB magnets, as follows: (1) acid baking, (2) employment of ultrasound-assisted water leaching, (3) the production of rare earth oxides (RE oxides) by a solution combustion method, and (4) a calcination process. There are several problems in conventional precipitation such as loss of a high amount of metal during precipitation and use of a high amount of precipitation agents. It is worth mentioning that the consumed precipitation agents in the solution are not easily recyclable. This study aims especially to investigate the production of RE oxides from recycled NdFeB magnets by solution combustion as an alternative to conventional precipitation methods. In this way, impurities that may have come to the system from the precipitation agents were prevented. Moreover, in the production of RE oxides via the above-mentioned method, precipitation agents and filtration steps were not necessary.