Removal of rare earth elements and thorium from LiCl-KCl molten salt by phosphate precipitation method

The removal of rare earth fission products and thorium from LiCl-KCl system is of great significance to purification and recovery LiCl-KCl during pyroprocessing flow. The removal efficiency of rare earth elements or thorium was investigated by adding precipitant Li3PO4 in LiCl-KCl molten salt. The characteristics of precipitation products were determined by XRD, SEM, and EDS analysis and the removal ratios of rare earth elements were compared under different conditions. The removal ratio of Th and rare earth elements (except Eu) can reach 95% when adding a slightly excess of Li3PO4 at 823 K. About 50% LiCl-KCl was entrained after precipitation reaction in mixture salt containing 20wt%ThF4, which showed the potential challenges to achieve the removal of Th and rare earth and the recovery of LiCl-KCl salt in the actual process. It is expected that the combination of precipitation and distillation method can improve to efficiently recover the LiCl-KCl mixed salt.