Production of lithium carbonate from brines - Patent 5993759 Lithium carbonate can be efficiently produced from a brine by (i) removing the boron therefrom, (ii) diluting the boron-free brine, (iii) removing magnesium from the diluted brine, and (iv) adding sodium carbonate to thereby precipitate lithium carbonate. By diluting the boron-free brine, the co-precipitation of lithium carbonate during the magnesium removal process is greatly reduced, thereby improving the recovery and purity of the lithium carbonate. Lithium, the third element in the Periodic Table, has an atomic weight of 6.939 and occupies No. 32 among the elements of the earth's crust with an average concentration of only approximately 20 ppm, which confers it the characteristic of a rare metal. Despite this fact, lithium is found distributed in numerous minerals due to its chemical reactivity. However, there are very few commercial sources for producing lithium, the main one of these being the mineral spodumene, which is a double lithium-aluminum silicate, LiAl (SiO In the invention, the brines are purified in sequential form, so that the first part of the boron is removed as commercial boric acid and then the rest of the boron is removed by means of solvent extraction utilizing an organic extractant. The brine devoid of boron is then purified in two stages. In the first stage, the brine is diluted with mother liquor generated in the precipitation stage of the lithium carbonate, or with similar brines, precipitating then over 70% of the magnesium contained in the brine utilizing a solution of sodium carbonate (soda ash), and precipitating only a minimum quantity of lithium carbonate together with the magnesium. The rest of the magnesium residue is precipitated in a second purification stage, where calcium hydroxide (milk of lime) is added for precipitating the magnesium as a hydroxide.
