E-pO2- Stability Phase Diagram of La3+ in LiCl-KCl Molten Salt

Abstract

This work concerns the electrochemical behaviors of La3+ on W electrodes in the LiCl-KCl-LaCl3 molten salt at 723-813 K. The results show that La3+ is reduced at about -2.04 V(vs. Ag/AgCl) on inert W electrode, which is a one-step three-electron transfer process. The redox potential, Gibbs free energy and activity coefficient of La3+/La are calculated by open circuit chronopotentiometry on W electrode in LiCl-KCl-LaCl3 molten salt. Potentiometric titration was used to study the reaction of lanthanum chloride with oxide ions. The titration curve shows that the precipitate of oxide is LaOCl. According to the experimental apparent electrode potential, activity coefficient and relevant thermodynamic data, the phase diagram of La-O stability was drawn. The stable phase diagram of E-pO2- shows that LaOCl is the most stable compound in the range of higher O2- concentration at 723 K.

Keywords

• licl-kcl
• e-po2-
• potentiometric titration
• thermodynamic properties