Extraction of Rare Earth Elements as Oxides from a Neodymium Magnetic Sludge

We propose a simple method for separating rare earth elements as oxides from a neodymium magnetic sludge by focusing on the affinity of oxygen for the rare earth elements (Nd, Dy, and Pr) and Fe. We have conducted separation experiments with a carbon crucible as contact material to confirm that carbon maintains the oxygen potential in the coexistence region of rare earth oxides and metallic Fe. In this work, the oxide phase of the rare earth elements and the alloy phase that primarily consists of Fe were separated clearly when the magnetic sludge in the carbon crucible was kept at 1823 K (1550 °C) under an Ar atmosphere. The purity of the rare earth oxide phase was high and only a small amount of rare earth elements were contained in the alloy phase. We found that the melting temperature of the rare earth oxides is a crucial factor for separation efficiency in our proposed method.