Electrochemical separation of cerium and lanthanum based on investigation of their cathodic behaviors in LiCl-KCl melt

摘要

Pyrochemical process for recycling spent metallic nuclear fuel, which is mainly conducted in molten salts, has attracted widely interests due to its obvious minimization of costs and waste outputs. As a simulate case, the electrochemical properties of Ce (III) and La(III) on molybdenum were investigated by cyclic voltammetry (CV), chronopotentiometry (CP) in LiCl-KCl melt at 773 K. And the influence of cathodic potential on the separation of cerium and lanthanum was also studied. The results showed that Ce3+ and La3+ were reduced by a single step mechanism under diffusion control. The diffusion coefficients of Ce3+ and La3+ deduced by CVs were 0.92×10-5 and 1.04×10-5 cm2/s, deduced by CP were 1.11×10-5 and 1.51×10-5 cm2/s, respectively. With the working potential shifted positively, the separation factor increased quickly. Though their reduction potentials were very close, a product with a purity of 99.7% was obtained from a feed in which the mole ratio of Ce:La was 20:1 by holding the cathodic potential at -2.2 V (vs. Ag/AgCl 2 mol.%).