Electrowinning and electrorefining of rare earth lanthanides using molten salt electrolytes is of interest because these technologies offer the potential for energy-efficient and low-cost recovery and reuse of these strategically important elements. However, efficient electrochemical processing of rare earth elements such as neodymium (Nd) is hindered by its multivalent nature. Specifically, the existence of Nd³⁺ and Nd²⁺ redox-active species can substantially lower the overall current efficiency of Nd electrorefining [1]. In the present talk, we will report on experimental and modeling investigations into the electrodeposition of Nd metal from NdCl₃-containing halide melts (eutectic LiCl-KCl). We will discuss how cyclic voltammetry studies and diffusion-reaction modeling help unravel the thermodynamic, kinetic and mass transport properties associated with the multivalent redox transitions prevalent during Nd electrodeposition. Furthermore, we will discuss how these properties can be used to design efficient Nd electrowinning and electrorefining processes. The broad applicability of our design approach will be discussed in the context of electrodeposition of other multivalent rare earth metals and alloys.

1. L. Feng, C. Guo, and D. Tang, J. Alloys Compd., 234, 183 (1996).