The effect of the cathode material nature on electroextraction of lanthanum in molten NaCl-2CsCl eutectic

For more effective recovery of lanthanum from spent fuel by molten salt electrolysis, the effect of different liquid cathodes on lanthanum was studied by electrochemical methods. The electrode reactions of the NaCl-CsCl-LaCl₃ solutions on the Mo, Pb, Pb-Ga, and Ga electrodes were investigated by cyclic, square-wave voltammetry and open-circuit chronopotentiometry over a wide temperature range. Electrodeposition of La(III) ions was established to be a one-step process. On the reactive Pb, Pb-Ga, and Ga electrodes, these processes occurred with depolarization and formation of the intermetallic compounds. It was found that the value of the exchange current density of La(III) ions on liquid cathodes increased in the order Pb < Pb-Ga < Ga. The redox potential of the La(III)/La couple was measured on the Pb, Pb-Ga, and Ga electrodes, and the principal thermodynamic characteristics of the alloys were calculated. Finally, Pb₃La and Ga₂La were successfully extracted from the molten salt via potentiostatic electrolysis.