Selective Formation of Rare-Earth–Nickel Alloys via Electrochemical Reactions in NaCl–KCl Molten Salt

Abstract

Toward the establishment of the electrochemical recovery process of rare-earth (RE) elements from used magnet scraps, selective electrochemical formation of RE–Ni alloys (RE = Pr, Nd, and Dy) was investigated in molten NaCl–KCl–NdCl3–DyCl3 and NaCl–KCl–PrCl3–NdCl3–DyCl3 at 973 K. Alloy samples were prepared by potentiostatic electrolysis using Ni plate electrodes at various potentials. The compositions of the formed alloys were analyzed using energy-dispersive X-ray spectroscopy (EDX), and the separation factors defined as {xDy/(xPr + xNd)}alloy were compared. High separation factors of 9.9 and 22.9 were obtained at 0.42 V and 0.45 V (vs. Na+/Na), respectively, indicating the possibility of effective separation and recovery of REs from the used magnet scraps. The optimum electrolysis condition was studied based on the discussion on the formation mechanism of RE–Ni alloys.