Electrochemical Removal of AlCl3 from LiCl-KCl Melts

Abstract

In order to remove impurity AlCl3 from LiCl-KCl melts before Li electrolysis, the Al3+ reduction potential on a tungsten electrode and the relation between Al3+ reduction peak current and AlCl3 concentration in LiCl-KCl-AlCl3 melts were determined by cyclic voltammetry (CV). Constant potential electrolysis at –1.6 V vs Cl2/Cl– on both solid Fe and liquid Zn cathodes was performed to remove AlCl3 impurity from the LiCl-KCl-AlCl3 melts. The removal rate of Al3+ from the melts was analyzed by both electrochemical methods and inductively coupled plasma–atomic emission spectrometry (ICP-AES) analysis. The results showed that 96.11 wt pct of Al were removed on a Fe cathode and 99.90 wt pct on a Zn cathode through 10 hours electrolysis, respectively. While stirring the melts by argon gas, 99.21 wt pct of Al3+ was separated from the melts by 4 hours of electrolysis at 723 K (450 °C), which effectively expedited the Al3+ electrochemical reduction rate and shortened the electrolysis time.