Systemic and Direct Production of Battery-Grade Lithium Carbonate from a Saline Lake

A process was developed to produce battery-grade lithium carbonate from the Damxungcuo saline lake, Tibet. A two-stage Li2CO3 precipitation was adopted in a hydrometallurgical process to remove impurities. First, industrial grade Li2CO3 was obtained by removing Fe3+, Mg2+, and Ca2+ from a liquor containing lithium. Second, industrial grade Li2CO3 was treated by CO2 to get the more soluble bicarbonates. EDTA-Li (lithium 2-carboxyhydrazine-1,1,2-tricarboxylate) was added to chelate Ca2+ and Mg2+. The decomposition of LiHCO3 produced insoluble Li2CO3 at 85 °C. The final precipitation yielded a high purity (99.6%) and homogeneous Li2CO3. Some factors affecting the production efficiency were investigated. The results showed that an L/S mass ratio of 30:1 favored the formation of a Li2CO3 slurry; a molar ratio of EDTA-Li to (Ca+Mg) 1.05:1 and hot water washing precipitate (L/S mass ratio 1:1) promoted ions removal; a cyclic use of filtrate improved the recovery of lithium.