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

Abstract

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. Keywords: Electrochemical extraction, Molten fluoride salt, Rare earth metals, Lanthanum