We proposed a new separation and recovery process for rare earth (RE) metals from scraps using molten salt and an alloy diaphragm. RE containing scrap is used as the anode. A RE-transition metal (TM) alloy is used as the diaphragm, which functions as a bipolar electrode. During electrolysis, all the RE metals in the anode are dissolved in the molten salt as RE ions. One or several specific RE ions are selectively reduced to form RE-TM alloys on the alloy diaphragm according to their formation potentials and/or alloying rates. Subsequently, the RE atoms chemically diffuse through the alloy diaphragm and are dissolved into the molten salt as RE ions in the cathode room. The permeated RE ions are finally deposited on the Mo or Fe cathode as RE metals. The RE ions remaining in the anode room can be collected by electrolysis using another cathode in the anode room. Almost all impurities remain in the anode room as residue or anode slime.

The present study focused on Fe alloys as alloy diaphragms. The electrochemical formation of Dy-Fe and Nd-Fe alloys in molten CaCl₂-LiCl systems at 873-973 K. To confirm the formation of Dy-Fe alloys, potentiostatic electrolysis was conducted at 0.30 V(vs. Li⁺/Li) and 0.50 V for 1 h using Fe plate cathodes at 873 K in CaCl₂-LiCl-DyCl₃ (0.50 mol% added). The two samples were analyzed by XRD. The alloy phases were identified as DyFe₂ or DyFe₃. On the other hand, potentiostatic electrolysis was conducted at 0.30 V and 0.50 V for 1 h using Fe plate cathodes at 873 K in CaCl₂-LiCl-NdCl₃ (0.50 mol% added). From the result of XRD analysis, it was found that several Nd-Fe phases were formed.