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.