Electrochemical separation of Th from ThO2 and Eu2O3 assisted by AlCl3 in molten LiCl–KCl

In this work, ThO2 and Eu2O3 were chloridized into ThCl4 and EuCl3 by AlCl3 in LiCl–KCl melts at 800 K, forming Th(IV) and Eu(III) ions. The co-reduction of Al(III), Th(IV) and Eu(III) ions on the tungsten electrode was studied by cyclic voltammetry and square wave voltammetry techniques in different AlCl3 containing systems. The results show that in the AlCl3-rich system, the potential disparity (ΔE) between Al–Th and Al–Eu alloys deposition is about 0.8 V, which is much higher than the necessary ΔE (0.20 V) for the separation of Th(IV) from Eu(III). Subsequently, the separation of Th from the melts was carried out on the aluminium electrode by the potentiostatic electrolysis at temperature of 800 K. The 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, in an AlCl3-rich system by the electrolysis at −1.8 V for 50 h, the very high separation factor (SF) of Th to Eu, and the excellent separation rate of Th were calculated to be >2.0 × 104 and >99.9%, respectively.