Effect of LiF on Gd Electrorefining in LiCl-KCl Molten Salt

The effect on Gd electrochemical and coordination behavior of addition of LiF in LiCl-KCl molten salt was studied, which indicates that the potential value of Gd and Tb is changed from 6 mV to 67 mV after addition of LiF in LiCl-KCl molten salt. The high temperature molten salt ion structure was analyzed by Raman spectroscopy and electrochemical methods. It is found that octahedron GdCl₆^3- and TbCl₆^3- exist in LiCl-KCl-GdCl₃ (5 mol%)/TbCl₃ (5 mol%) molten salts. The effect on Gd and Tb ion structures of addition of LiF in LiCl-KCl molten salt was also studied. The result shows that octahedron GdF₃Cl₃^3-/TbF₃Cl₃^3- exist coordinated three F^- and Cl^-, and their cumulative stability constants are 10.98 and 6.38, respectively. Based on the result above, the effect on Gd electrorefining of addition of LiF in LiCl-KCl molten salt was studied, and the result shows that Gd can be separated as a high decontamination factor with addition of LiF in LiCl-KCl molten salt.