Electrochemical and Kinetic Analysis of Lu(III) Extraction by Liquid Ga Electrode in NaCl-CaCl₂ Melt

This study systematically investigates the electrochemical behavior of Lu(III) on inert molybdenum (Mo) and liquid gallium (Ga) electrodes in NaCl-CaCl 2 molten salt at 923 K. A combination of cyclic voltammetry (CV), square wave voltammetry (SWV), and reverse chronopotentiometry (RCP) was employed to elucidate the underlying electrochemical mechanisms. The diffusion coefficients of Lu(III) ions were determined from chronopotentiometry (CP) measurements. Lu-Ga intermetallic compounds were formed via the co-deposition of Lu(III) and Ga(III) on an inert electrode. Thermodynamic properties, including equilibrium potential and Gibbs free energy change of formation, were evaluated using open-circuit potential (OCP) measurements. Additionally, linear polarization (LP) analysis was performed to investigate the kinetics of the Lu(III)/Lu reduction on Mo and liquid Ga electrodes, yielding exchange current densities and charge transfer resistance at various temperatures. Furthermore, constant potential electrolysis (CPE) at different potentials (−1.4 V, −1.6 V, −1.7 V on liquid Ga and −1.9 V on Mo) for 15 h enabled the recovery of Lu(III) from the molten salt. Metallic Lu and Ga 3 Lu formed on Mo and liquid Ga electrodes respectively. The formed metallic Lu and Ga 3 Lu were characterized by XRD. Lu extraction rates reached 95.59% on Mo and 98.99% on liquid Ga, showing the latter’s higher efficiency.