METHOD FOR OBTAINING NANO-SIZED CALCIUM CARBONATE Russian patent published in 2023 - IPC C01F11/18 B82Y40/00 

FIELD: chemical technology.

SUBSTANCE: invention relates to a method for producing nano-sized calcium carbonate from natural raw materials in the form of limestone or chalk. Before calcination, carbonate raw materials in the form of limestone or chalk with a CaCO₃ content of at least 98% are washed with water and treated with a 1% H₂O₂ solution for 24 hours. The purified raw materials are filtered and dried at 105°C for 8 h and crushed. Calcined carbonate raw materials at 850°C for 2 h, while the exiting CO₂ is concentrated in a container. CaO is dispersed for 4 h in purified water at 80°C using an ultrasonic vibrator with a frequency of 20,000 Hz and filter the Ca(OH)₂ suspension. Ca(OH)₂ is carbonated for 3-4 hours by supplying the carbonate raw material CO₂ released during calcination, at a gas supply rate of 20-30 l/h. Bubbling is stopped when the pH drops to 7. The resulting CaCO₃ precipitate with a particle size of 50-70 nm is washed, dried at 105°C and fine grinding is performed. The unreacted CO₂ is reused for bubbling, and the water from the reactor, after separating the CaCO₃ precipitate, is reused in the hydration stage.

EFFECT: method is less energy-consuming and environmentally friendly due to the preventing CO₂ from getting into the atmosphere.

1 cl, 4 dwg, 2 ex