METHOD OF PRODUCING HIGH-PURITY CALCIUM FLUORIDE Russian patent published in 2011 - IPC C01F11/22 

FIELD: chemistry.

SUBSTANCE: invention relates to production of calcium fluoride used in production of ceramics, fluoride glass and fibre-optic materials. Before fluorination, aqueous calcium nitrate solution is purified from metal impurities by mixing with aluminium nitrate nano-hydrate at a rate of 50-80 rpm, where the said aluminium nitrate nano-hydrate is taken in amount of 2% of the weight of anhydrous calcium nitrate. The formed solution is leached to pH 8.0-8.2, heated to 60-70°C and the cooled aqueous solution separated from the precipitate on a vacuum filter. The purified aqueous calcium nitrate solution is fed into a reactor for the fluorination step together with 5-25% hydrofluoric acid and with 10% stoichiometric excess. The process is carried out at temperature 50-60°C while stirring at a rate of 700-900 rpm. The filtered product is washed with water and then dried at temperature 120-150°C.

EFFECT: invention enables to obtain high-purity calcium fluoride containing over 99,9 wt % basic substance, which meets requirements for fibre-optic products.

4 cl, 2 ex