GB804962A - Preparation of high purity lithium carbonate from lithium ores - Google Patents

Abstract

High purity lithium carbonate is obtained by treating an aqueous solution containing 2 to 44 per cent, preferably 15 to 30 per cent, by weight of lithium chloride together with a substantial concentration sodium chloride or potassium chloride or both with sodium carbonate, heating the resulting mixture to 60 DEG to 100 DEG C., preferably 95 DEG to 100 DEG C., and separating solid lithium carbonate from the heated mixture. The lithium chloride solution may be obtained by roasting lithium ore, preferably containing 2 to 9 per cent lithium oxide, with calcium carbonate and chloride, whereby gaseous crude lithium chloride is evolved, which is dissolved in the mother liquor chloride solution remaining after the separation of solid lithium carbonate. In one form of the invention pegmatite ore is coarsely ground, and the a -spodumone constituent is concentrated e.g. by flotation. This is heated to convert it into b -spodumone, ground, and passed through a magnetic separator to remove iron oxide. The b -spodumene is mixed with sand, calcium carbonate and calcium chloride and passed through a cement kiln at 1100 DEG to 1200 DEG C., leaving a portland cement clinker and forming gaseous lithium chloride, contaminated with sodium and potassium chlorides, which is condensed to a dust in a heat exchanger. The dust is collected, extracted with water, and the insoluble residue returned to the kiln. The solution is combined with alkali metal chloride solution and solids from elsewhere in the process and the resulting slurry is brought to 25 DEG to 30 DEG C. when fairly pure solid sodium chloride is recovered. To the liquid is added anhydrous sodium carbonate and the temperature raised to 80 DEG to 100 DEG C., thereby forming pure lithium carbonate which is recovered. The mother liquor is concentrated to a solids concentration of 55 per cent and crude sodium chloride is separated and recycled to the next batch of crude aqueous lithium chloride solution. The barren liquor is cooled to 0 DEG to 5 DEG C., when fairly pure solid potassium chloride separates and is recovered, and the residual liquor is recycled to the initial crude aqueous chloride solution.ALSO:A high grade Portland cement clinker of low magnesium and iron content is obtained as a by product when a mixture of beta-spodument, sand, limestone, and calcium chloride is roasted during the preparation of lithium carbonate (see Group III].