METHOD FOR PRODUCING HIGH PURITY LITHIUM HYDROXIDE MONOHYDRATE FROM MATERIALS CONTAINING LITHIUM CARBONATE OR LITHIUM CHLORIDE

摘要

The invention relates to the field of chemical processes for producing inorganic compounds, and more particularly to methods for producing high-purity lithium hydroxide monohydrate from materials containing lithium carbonate or lithium chloride. Essence of the invention: a solution of lithium chloride is prepared by dissolving lithium carbonate in hydrochloric acid formed, according to different embodiments, from chlorine gas produced as a result of the electrolysis of a solution of lithium chloride, or by dissolving solid lithium chloride in water. Impurities contained in the materials pass into the resulting solution. To purify said solution of calcium and magnesium impurities, lithium hydroxide formed in the electrolysis process is used, followed by resin-based ion exchange. The purified solution of lithium chloride has high electrical conductivity, making it possible to carry out the process of lithium chloride to lithium hydroxide conversion in an electrolytic cell. Sulphate ions also accumulate in the anolyte, lowering the lifespan of the anodes. To purify the anolyte of said ions, a portion of the anolyte is removed and treated with barium chloride, the resulting barium sulphate is filtered, and the anolyte is returned to the electrolysis process. The concentration of lithium hydroxide in the catholyte is maintained at a level of 40-80 g/l to keep the total cost of the electrolysis process and subsequent evaporation of the LiOH solutions to a minimum. The LiOH is purified of Na+ and K+ impurities by recrystallization, a portion of the resulting mother solution is carbonized with carbon dioxide produced in the step of neutralizing lithium carbonate with hydrochloric acid. The lithium carbonate produced is returned to the hydrochloric acid neutralization operation. The proposed methods make it possible to use materials containing lithium carbonate or lithium chloride to produce high-purity lithium hydrochloride monohydrate.