METHOD OF PRODUCING CALCIUM CARBONATE Russian patent published in 2018 - IPC C01F11/18 C09C1/02 

FIELD: technological processes.

SUBSTANCE: invention relates to isolation and purification of calcium carbonate. Method for producing calcium carbonate from a calcium-containing concentrate is described, which includes dissolving the concentrate in hydrochloric acid, processing the concentrate in four steps, while in the first three steps, the precipitation of calcium in the form of oxalate is carried out in the presence of tartaric and oxalic acid in an ammonia medium, its subsequent separation and calcination to calcium carbonate, in the second step the preliminary separation of heavy metal impurities in the form of sulfides, at the fourth step, the dissolution of calcium carbonate in acid is carried out, the precipitation from the purified solution of calcium carbonate, its separation and heat treatment, characterized in that the dissolution of calcium carbonate in the second step is carried out in 2N hydrochloric acid, heavy metal impurities precipitate as sulphides in the presence of ammonia at pH 8 and temperature of 60 °C, in the fourth step, the carbonate is dissolved in 2N hydrochloric acid.

EFFECT: developed method for the purification of calcium carbonate ensures the effective separation of impurities, increase in the yield of isotopically enriched calcium up to 99,6 % with a purification degree of 99,988 %.

1 cl, 6 ex