Abstract
Rare earth elements (REEs) have a crucial role towards low carbon green economy and clean society. A quarter of total global REEs production is used to produce permanent magnets which have high recycling value. In this study, a high-temperature oxidation process is used to selectively oxidize REEs in the magnet using Fe2O3 as an oxidizing agent. B2O3 is added as a flux to lower the slag melting temperature and for selective recovery of REEs. In this study, the effect of flux and oxidizing agent amount was investigated on both cerium-rich NdFeB and other NdFeB magnets. At 1350 °C for 1 h with the addition of 0.8 stoichiometric amount of Fe2O3 and 45 wt% of B2O3, the slag phase was successfully separated from the metallic phase primarily metallic iron. Microstructural analysis showed that REEs in the magnet did not report to the metal phase while the REE-rich slag phase contained almost no iron or other exogen elements. After the selective removal of iron, REEs were recovered from the slag through an acid-leaching process. The process proposed in this study is reagent and energy-efficient for NdFeB and NdCeFeB magnets as iron can be removed in the initial smelting step.
