A membrane electrodialysis process was tested for obtaining battery grade lithium hydroxide from lithium brines. Currently, in the conventional procedure, a brine with Li+ 4-6 wt% is fed to a process to form lithium carbonate and further used to produce lithium hydroxide. The disadvantages of this process are its high cost due to several stage requirement and the usage of lime, causing waste generation. The main objective of this work is to demonstrate the feasibility of obtaining battery grade lithium hydroxide monohydrate, avoiding production of lithium carbonate. A laboratory cell was constructed to study electrochemical kinetics and determine energetic parameters. The effects of current density, electrode material, electrolyte concentration, temperature and cationic membrane (Nafion 115 and Nafion 117) on cell performance were determined. Tests showed that a current density of 1200 A/m2 and temperatures between 75-85 °C allow reduced specific electricity consumption (SEC) (7.25 kWh/kg LiOH). A high purity product is obtained at temperatures below 75 °C, with a Nafion 117 membrane and low electrolyte concentration. Resulting key electrochemical data would enable a pilot-scale process implementation to obtain lithium compounds.
Keywords: electrochemical kinetic; lithium brines; lithium hydroxide; membrane electrodialysis; operating conditions; specific electrical consumption.