Green molten salt electrolysis for lanthanum recovery: A study on liquid aluminum electrode in NaCl-KCl eutectic melt

Effective extraction of lanthanum (La) from spent nuclear fuel is crucial for promoting the sustainable use of nuclear energy. Liquid aluminum (Al) electrode shows significant advantages as active cathodes in the electrochemical extraction of lanthanides (Ln). However, the electrolytic reduction of La by liquid Al in NaCl-KCl melt has not received adequate attention and understanding. For this reason, the electrochemical recovery of La from NaCl-KCl melt using a liquid Al cathode has been investigated in this paper by a series of electrochemical methods. The results indicate that the reduction of La(III) on the W electrode occurs as a one-step process and the reaction is irreversible. The diffusion coefficient of La(III)/La was determined to be 6.70×10 -5 cm 2 s -1 . Meanwhile, the co-reduction process of La(III) and Al(III) on the W electrode was systematically investigated to explore the potential for forming binary intermetallic compounds. In addition, the exchange current density (0.025-0.030   A   cm -2 ) at different temperatures was determined using linear polarization (LP), further elucidating the temperature dependence of the exchange current density. Finally, La was successfully extracted as an alloy by potentiostatic electrolysis on the Al electrode. This study provides promising insights for the extraction of La in NaCl-KCl melt on liquid Al electrode.