Electrochemical extraction of lanthanum in molten fluoride salts assisted by KF or NaF

Separation of some active metal ions such as Ce3+, Eu3+, and La3+ from molten fluoride salt using electrochemical process is difficult. The currently available electrodeposition process assisted by the solid reactive electrode or liquid metal electrode faces challenges such as the isolation of the reactive electrode due to the formation of a compound, the ability to maintain a low activity value of the active metal in liquid electrode, and a complex purification process of the target metal. In the present study, we developed a new method that successfully proved the extraction of lanthanum from molten LiF salt using an inert Mo electrode with the assistance of either NaF or KF salt. In that case, the formation of LaF63− in LiF-KF (or LiF-NaF) salt, instead of La3+ in LiF, positively shifts the electrodeposition potential of lanthanum by a value of about 1 V. The simplicity of this method compared to the conventional routes for the extraction of lanthanum from molten salt will result in a reduction in separation costs and this approach has a potential application for the separation of other active metals in molten fluorides or chlorides. •Electrochemical tests were performed in LiF-LaF3, LiF-KF-LaF3, and LiF-NaF-LaF3, respectively.•The electrodeposition of La metal in LiF-KF and LiF-NaF molten salts was realized and further confirmed by SEM analyses.•Electrodeposition of lanthanum was found to be greatly shifted to a more positive value with the addition of KF or NaF.