Electrochemical separation of Mn(II) impurity from molten salt electrolyte for magnesium electrolysis

• Mn(II) reduction on tungsten electrode is quasi-reversible and diffusion-controlled, with kinetic parameters determined at 973–1048 K. • Controlled-potential electrolysis at −1.5 V for 8 h reduced MnCl2 impurity from 0.62 wt.% to 0.037 wt.%, achieving 94.14% removal efficiency. • Removal of Mn(II) impurity significantly improved magnesium purity from 98.59% to 99.94% and promoted formation of large globules. • The proposed method is green and effective for separating metal ion impurities in molten salt electrolytes for high-purity magnesium production.