Recovery of Dy from a Mixture of Nd, Fe, B and Dy by Electrolysis in Molten LiCl

Abstract

The electrodeposition and recovery of Dy was attempted by chlorinating Dy with Cl₂ generated at the anode by electrolysis in molten LiCl, in which Fe, B, Nd and Dy powders were added, then reducing the Dy ions, which were ionized from the dysprosium chloride, at the cathode. When the electrolysis in the LiCl bath was carried out even after the Fe, B, Nd and Dy powders were added to the LiCl bath, the electrodeposition of these metals on the cathode did not occur, thus the metals could not be recovered when the electrolysis in the LiCl bath was carried out even after the Fe, B, Nd and Dy powders were added to the LiCl bath. The mass increase due to the electrodeposition of Dy was observed at the cathode in the LiCl bath in which DyF₃ was added. The mass of the material electrodeposited at the cathode was greater in the LiCl bath, in which the Fe, B, Nd and Dy powders were added with DyF₃, in comparison to that in the bath with only DyF₃. It was found from analyzing the electrodeposited material by an X-ray diffraction technique and an electron probe microanalyzer that the material consisted of a large amount of Dy and a small amount of B. Examination of the cation concentration in the molten salt after electrolysis using an inductively coupled plasma instrument revealed that the molten LiCl, into which DyF₃ and the metal powders were added, contained the highest number of Dy ions. Thus, metallic Dy was cationized during the electrolysis in the molten LiCl bath containing DyF₃ and the metal powders, then the cationized Dy was reduced at the cathode and precipitated as metallic Dy.