In Situ Production\nof Carbonate Anions from Water\nElectrolysis and CO<sub>2</sub> Absorption for Li<sub>2</sub>CO<sub>3</sub> Crystallization from Preconcentrated Brines

Lithium carbonate (Li<sub>2</sub>CO<sub>3</sub>) is normally\ncrystallized\nfrom concentrated brines via the addition of sodium carbonate (Na<sub>2</sub>CO<sub>3</sub>, soda ash). While this is a methodology largely\nproved and in implementation in almost all facilities in operation\ntoday, it is a chemical intensive procedure. Both the associated costs\nof sodium carbonate and the logistic issues of bringing large amounts\nof chemicals to the remote locations where lithium mining from brines\ntakes place should be considered. Here a new prospective technology\nis proposed for the in situ production of carbonate anions via water\nreduction and direct CO<sub>2</sub> absorption on alkaline media.\nExperiments were performed on a real concentrated brine sample obtained\nfrom an operating facility in the Lithium Triangle. In the first electrolysis,\ntraces of divalent cations were removed with only 1.3% of the total\nLi<sup>+</sup> content in the original brine being trapped in the\nobtained solid. The second electrolysis produced removal from the\nbrine from 67.2% of the originally contained Li<sup>+</sup>. Studies\nwere conducted to improve the purification of the solid, since in\nthe highly saline brine (total dissolved solids of 412 g L<sup>–1</sup>) the as obtained solid was only 70.5% pure. Upon 2 purification\nsteps, a solid 99.1% pure could be obtained. A third electrolysis\nstep could crystallize further 11.8% extra of the original Li<sup>+</sup> content, albeit at a much higher energy cost. Upon brine\ntreatment, 88.0 g CO<sub>2</sub> per liter of brine fed to the first\nelectrolysis could be absorbed; 63.2 g of which remain in the Li<sup>+</sup> depleted brine, and only 24.8 g in the obtained solids.