METHOD OF PRODUCING HIGH-PURITY CALCIUM CARBONATE Russian patent published in 2011 - IPC C01F11/18 

FIELD: chemistry.

SUBSTANCE: invention relates to production of highly pure carbonates of alkali-earth metals used in optical glass manufacturing and fibre optics. To obtain calcium carbonate, initial calcium nitrate solution is undergoes pre-treatment with aluminium nitrate in amount of 2% of the mass of anhydrous calcium nitrate and with alkali to pH 8.0-8.3, followed by separation of the solution from the precipitate. Calcium carbonate is then chemically precipitated from the cleaned calcium nitrate solution using carbon dioxide gas which is fed into the reactor simultaneously with the stream of cleaned calcium nitrate solution and a stream of ammonia gas or its aqueous solution. Chemical precipitation is carried out using stoichiometric amounts of reagents, temperature of 42-45°C, pH 7.8-8.2 and while stirring the reaction mixture at 900-1000 rpm. The obtained product is separated via filtration, washed with clean water and dried at 115-125°C.

EFFECT: invention increases efficiency of the process of producing calcium carbonate and purity of the obtained product.

2 cl, 4 ex