Recovery of Rare Earth Metals in Used Magnets by Molten Magnesium

Abstract

We report here Hitachi's approach to recycle rare earth (RE) metals in used magnets by using molten magnesium (Mg). The process consists of 3 steps; (1) extraction of RE metals from magnets into molten Mg, to form Mg-RE melt, (2) mechanical separation of magnets from the Mg-RE melt, ??) collection of RE metals by evaporation of Mg in the Mg-RE melt. In the step 1, extraction of RE metals proceeds rapidly and completes in about 3 h. The efficiency strongly depends on the temperature (T) and Mg/magnet ratio (??). One of the optimal conditions is T=1273 (K) and r| is 10, where the efficiencies for Nd and Dy extraction are almost 100 % and 60 %, respectively. Further increase of Dy extraction efficiency is possible by addition of Ca to suppress the oxidation of Dy.