Production of highly pure lithium chloride from impure brines

Abstract

Highly pure lithium chloride suitable for use in production of lithium metal by electrolysis is obtained directly from impure natural or other lithium chloride brines by an integrated process in which the brine is first concentrated by solar energy to a lithium chloride concentration of about 3%, after which the brine is treated with lime and calcium chloride to convert such impurities as boron, magnesium and sulfate to a calcium borate hydrate, magnesium hydroxide and calcium sulfate dihydrate, respectively, and separating the precipitated calcium sulfate dihydrate from the brine. The brine is then further concentrated to 40% or more lithium chloride by means of solar or other energy, during which concentration step the calcium borate hydrate, magnesium hydroxide and calcium sulfate dihydrate precipitate from the brine. The highly concentrated brine is subjected to evaporation at a temperature above 101.degree. C. to produce anhydrous lithium chloride which is further heated to a temperature of 200.degree. C. or more, followed by extraction of the lithium chloride with isopropanol. After removal of solvent a highly pure lithium chloride product is obtained.