Separation of Nd metal by using disproportionation reaction of Nd(II) in molten chlorides

In order to separate neodymium (Nd) from lanthanides in chloride melts, the electrochemical characteristics Nd ions in molten LiCl–CaCl2 eutectic were studied. The formal redox potentials of the Nd3+|Nd2+ and Nd2+|Nd couples in molten LiCl–CaCl2 eutectic at 823 K were determined to be −2.745 ± 0.005 and −3.081 ± 0.005 V vs. Cl2|Cl−. Under the controlled potential electrolysis by applying negative potential to form Nd2+, Nd2+ was disproportionated to Nd3+ and metallic Nd fog according to the reaction; 3Nd2+ ⇄ 2Nd3+ + Nd. When a quartz glass was immersed in the melt during the electrolysis, Nd was coated on the quartz surface. The chemical composition of the recovered Nd was analyzed to be Nd metal and Nd2O3 by scanning electron microscopy, X-ray diffractometry, and electron probe microanalysis. The same electrolytic method was carried out under the coexistence of Nd3+ and lanthanum ion (La3+). Nd3+ was separated from La3+ and recovered to be Nd2O3.