Electrochemical Formation of Pr-Ni Alloys in LiF-CaF2-PrF3 and NaCl-KCl-PrCl3 Melts

Abstract

For the establishment of a process for the electrochemical recovery of rare earth elements from used magnet scraps, the electrochemical formation of Pr–Ni alloys in molten LiF–CaF2–PrF3 and NaCl–KCl–PrCl3 salts at 1123 K and 973 K, respectively, was investigated. Cyclic voltammetry and open-circuit potentiometry indicated the formation of several phases of Pr–Ni alloys. Alloy samples were prepared by one- or two-step potentiostatic electrolysis using a Ni plate electrode at various potentials. Scanning electron microscopy observations and X-ray diffraction measurements confirmed the formation of PrNi2, PrNi3, Pr2Ni7, and PrNi5. The formation potential for each Pr–Ni alloy phase was determined from experimental results. In addition, the optimum electrolysis conditions for the separation of Nd, Dy, and Pr are discussed.