Lithium recovery by means of electrochemical ion pumping: a comparison between salt capturing and selective exchange

Currently, lithium carbonate is mainly produced through evaporation of lithium-rich brines, which are located in South American countries such as Bolivia, Chile, and Argentina. The most commonly used process, the lime-soda evaporation, requires a long time and several purification steps, which produces a considerable amount of chemical waste. Recently, several alternative electrochemical methods, based on LiFePO4 as a selective lithium capturing electrode and differing for the reaction at the counter electrode, have been proposed. In this work a comparison between the salt capturing method, based on silver / silver chloride reaction, and the selective exchange method, based on ion intercalation reaction in a Prussian Blue derivative, is performed in terms of energy consumption. In particular, the energy consumption is divided in thermodynamic and kinetic contribution, and the theoretical calculations are compared with the experimental results. The experimental results show a good agreement with the theoretical calculation. The selective exchange method shows superior performances to the salt exchange in terms of purity and efficiency, however the energy consumption is higher.