Electroseparation of thorium from ThO₂ and La₂O₃ by forming Th-Al alloys in LiCl-KCl eutectic

In this work, AlCl₃ was employed to chloridize ThO₂ and La₂O₃ with the formation of ThCl₄ and LaCl₃ in the LiCl-KCl eutectic at 773 K. The chlorination can be accomplished in less than one hour, displaying a fast chlorination kinetic. Cyclic voltammetry (CV) technique was used to evaluate the feasibility of the separation of Th⁴⁺ from La³⁺ through forming Th-Al alloys. The results showed that the disparity between the deposition potentials of Th-Al and La-Al alloys was approximately 0.2 V at 773 K, which is theoretically sufficient for the separation of Th⁴⁺ from La³⁺. Subsequently, the separation of Th⁴⁺ from La³⁺ was carried out on Al cathodes by galvanostatic electrolysis and potentiostatic electrolysis at the temperature of 773 K. During the separation process, the concentrations of Th⁴⁺ and La³⁺ ions were monitored by both Square Wave Voltammetry (SWV) on a W electrode and ICP-AES analysis of the melt. The deposited products were characterized by the scanning electron microscopy (SEM) with energy dispersive spectrometry (EDS), X-ray diffraction (XRD) and inductively coupled plasma atomic emission spectrometer (ICP-AES). Finally, by potentiostatic electrolysis at −1.20 V for 48 h in an Al³⁺ ion sufficient system, the recovery rate of Th was determined to be 97.1%. In addition, the separation factor (SF) of Th to La of 1367.4 was achieved