The Behavior of Additives LiF and KF on Current Efficiency in Aluminium Electrolysis

The effect of KF and LiF contents in the melt electrolyte on current efficiency were investigated during aluminum electrolysis using base NaF−AlF₃−Al₂O₃−CaF₂ system at 980°C in laboratory scale. The electrolysis was performed with a cryolite ratio of 2.5 and with 4% Al₂O₃ and 5% CaF₂. The duration of each electrolysis experiment was 4h with a graphite anode and a cathodic current density of 0.85Acm^-2. The current efficiency was found to vary with the lithium fluoride and potassium fluoride concentration. The effects of KF and LiF on the cathode process were studied using the same system. The alkali metals concentration including K, Na and Li in aluminium were analyzed as a function of the cathodic current density. Results are presented from a study of the influence of electrolyte composition and cathodic current density on current efficiency and cathode process. Also the influence of LiF on current efficiency was studied in an industrial cell.