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

Abstract In order to separate neodymium (Nd) from lanthanides in chloride melts, the electrochemical characteristics Nd ions in molten LiCl–CaCl 2 eutectic were studied. The formal redox potentials of the Nd 3+ |Nd 2+ and Nd 2+ |Nd couples in molten LiCl–CaCl 2 eutectic at 823 K were determined to be −2.745 ± 0.005 and −3.081 ± 0.005 V vs. Cl 2 |Cl − . Under the controlled potential electrolysis by applying negative potential to form Nd 2+ , Nd 2+ was disproportionated to Nd 3+ and metallic Nd fog according to the reaction; 3Nd 2+ ⇄ 2Nd 3+ + 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 Nd 2 O 3 by scanning electron microscopy, X-ray diffractometry, and electron probe microanalysis. The same electrolytic method was carried out under the coexistence of Nd 3+ and lanthanum ion (La 3+ ). Nd 3+ was separated from La 3+ and recovered to be Nd 2 O 3 .