METHOD OF PRODUCING MICROSILICA FROM NATURAL DIATOMITE BY PRECIPITATION OF NITRIC ACID SOLUTION Russian patent published in 2021 - IPC C01B33/18 C01B33/193 

FIELD: construction.

SUBSTANCE: invention relates to construction materials, specifically to production of modified additives for concrete, mortar, dry construction mixtures, heat-insulating materials. Disclosed is a method of producing microsilica from natural diatomite by precipitation of a solution of HNO₃, including preliminary calcination of diatomite at temperature of 500 °C for 30–120 minutes, grinding, after which ground and calcined diatomite is treated using 30 % NaOH solution, where the ratio of liquid and solid phases is equal to 14:1, at the temperature control temperature of 90 °C for 2 hours, then formed precipitate is separated and SiO₂ is precipitated with solution of concentrated HNO₃ to acid reaction of solution pH 1–2, followed by washing and drying the filter cake, which is then transferred into a Petri dish and dried at 100–160 °C in a drying cabinet to constant weight.

EFFECT: technical result is invention increases output of finely dispersed amorphous chemically pure microsilica with minimum content of impurities from natural diatomite by precipitation of HNO₃ solution to 87.2 %, where content of SiO₂ is 95.36÷99.63 %, and also to save time for washing residue with water to remove chloride ions.

1 cl, 3 tbl