Abstract
A new process is proposed for the separation and recovery of rare-earth metals from magnet scraps. In order to investigate the electrolysis potential for the separation of Dy and Nd, cyclic voltammetry was conducted using a Ni electrode in a molten LiCl-KCl-DyCl3 or LiCl-KCl-NdCl3 system at 723 K. In cathodic scanning with the Ni electrode, a cathodic current was observed from 1.00 V (vs. Li+ / Li) as a result of the formation of Dy-Ni alloys in the molten LiCl-KCl-DyCl3 system. In contrast, a cathodic current as a result of the formation of Nd-Ni alloys was observed from 0.60 V in the molten LiCl-KCl-NdCl3 system. These results suggested that the separation of Dy and Nd could be achieved in the potential region 0.60-1.0 V. On the basis of the cyclic voltammetry results, an alloy sample was prepared by potentiostatic electrolysis at 0.65 V for 1 h using a Ni plate cathode in a molten LiCl-KCl-DyCl3-NdCl3 system. ICP-AES showed that the mass ratio of Dy/Nd in the alloy sample was 72. This result indicated the possibility of selective separation of Dy and Nd in a molten LiCl-KCl-DyCl3-NdCl3 system. Another investigation was performed in a molten LiCl-KCl-DyCl3-LaCl3 system, with and without FeCl2, in order to confirm the selectivity. Regardless of the presence of FeCl2, DyNi2 was selectively formed on a Ni plate cathode by potentiostatic electrolysis at 0.55 V, which indicates a high possibility of separating Dy and La (Fe).
