Process analysis and study of factors affecting the lithium carbonate crystallization from sulfate media during lithium extraction

Abstract

Lithium carbonate is the primary product of the lithium extraction process and is an important compound for the battery making industry. A major step in the conventional sulfuric acid extraction of lithium from mineral ore is the precipitation of lithium carbonate from lithium sulfate media by sodium carbonate addition. Because of the high solubility of lithium carbonate in water and challenges with separating and removing sodium sulfate from the product, this step has a low lithium recovery efficiency as lithium carbonate, and it is difficult to achieve the desirable product purity. In this study, the crystallization process of lithium carbonate is investigated thoroughly. The effect of several operating parameters, including initial salt concentration, reaction temperature, impurity presence, seeding, and feeding rate of sodium carbonate solution to lithium sulfate solution on the lithium recovery efficiency, product purity, reaction equilibrium time, product particle size and crystal morphology is investigated. Results indicate that mixing the lithium sulfate and sodium carbonate solutions both at 2.0 mol/L concentration at 45 °C and 300 rpm agitation rate followed by cooling crystallization of sodium sulfate byproduct produces lithium carbonate with 90% lithium recovery and 99.0% purity. With additional dissolution and recrystallization steps, a lithium carbonate product with over 99.5% purity is produced.