CALCIUM CARBONATE PRODUCTION PROCESS Russian patent published in 2003 - IPC

FIELD: inorganic compounds technology. SUBSTANCE: calcium-containing concentrate with elevated amount of impurities (copper, chromium, iron, lead, magnesium, aluminum, manganese) is dissolved in aqueous HCl on heating. Resulting solution is supplemented by tartaric acid, ammonia to pH 10-11, and oxalic acid. Calcium oxalate is separated, calcined at 600 C, and dissolved in aqueous HCl at pH 2-3. Gaseous H₂S is then passed through solution to precipitate heavy metal sulfides, which are filtered off. More calcium oxalate is precipitated from solution as above, calcined and dissolved in acetic acid to pH 2-3. To thus purified solution, ammonium carbonate-saturated ammonia solution is added to pH 11-12, purified calcium carbonate filtered off and thermally treated for 6 h at 200-300 C. Yield of isotope-enriched calcium in the form of 99.95% calcium carbonate is 99.2% without loss of calcium. EFFECT: increased yield of product and its purity using conventional equipment, inexpensive and accessible reagents. 7 ex