Method for producing calcium carbonate, calcium carbonate, and method for growing calcium carbonate crystals
Provided are a method for producing calcium carbonate having a controlled size and a method for growing crystals in order to produce calcium carbonate having a controlled size. A method for producing a calcium carbonate comprises the steps of reducing the pH of an aqueous calcium carbonate dispersion to 9.0 or less and then increasing the pH of the aqueous calcium carbonate dispersion to grow calcium carbonate particles.
1 . A method for producing calcium carbonate having the calcite structure, having a BET specific surface area of 2 to 50 m 2 /g, and having a number-based average particle size of 30 nm to 1.0 μm as determined by electron microscopy, the method comprising at least a step of facilitating growth of calcium carbonate crystals from an aqueous calcium carbonate dispersion, the step of facilitating growth of calcium carbonate crystals comprising:
reducing a pH of the aqueous calcium carbonate dispersion to 6.2 or less and 5.5 or more by adding carbonated water at atmospheric pressure; and then
allowing calcium carbonate particles to grow and then increasing the pH above 6.2 of the aqueous calcium carbonate dispersion.
2 . The production method according to claim 1 , wherein the reducing the pH of the aqueous calcium carbonate dispersion to 6.2 or less and 5.5 or more and the increasing the pH of the aqueous calcium carbonate dispersion are repeated.
3 . The production method according to claim 1 , wherein increasing the pH of the aqueous calcium carbonate dispersion is performed by a method selected from the group consisting of allowing the aqueous calcium carbonate dispersion to stand, stirring the aqueous calcium carbonate dispersion, depressurizing the aqueous calcium carbonate dispersion, heating the aqueous calcium carbonate dispersion, and adding a basic substance to the aqueous calcium carbonate dispersion.
4 . A method for producing calcium carbonate having the calcite structure, having a BET specific surface area of 2 to 50 m 2 /g, and having a number-based average particle size of 30 nm to 1.0 μm as determined by electron microscopy, the method comprising at least a step of facilitating growth of calcium carbonate crystals from an aqueous calcium carbonate dispersion, the step of facilitating growth of calcium carbonate crystals comprising:
reducing a pH of the aqueous calcium carbonate dispersion to 9.0 or less and 5.5 or more by performing following a. or b.:
a. adding an acidic substance selected from the group consisting of hydrochloric acid, sulfuric acid, hydrobromic acid, boric acid, benzenesulfonic acid, acetic acid, citric acid, tartaric acid, and ascorbic acid at atmospheric pressure, or
b. adding an acidic substance at higher than the atmospheric pressure and less than 10 atm; and then
increasing the pH of the aqueous calcium carbonate dispersion to grow calcium carbonate particles.
5 . The production method according to claim 4 , wherein increasing the pH of the aqueous calcium carbonate dispersion is performed by a method selected from the group consisting of allowing the aqueous calcium carbonate dispersion to stand, stirring the aqueous calcium carbonate dispersion, depressurizing the aqueous calcium carbonate dispersion, heating the aqueous calcium carbonate dispersion, and adding a basic substance to the aqueous calcium carbonate dispersion.
6 . The production method according to claim 4 , wherein the reducing the pH of the aqueous calcium carbonate dispersion to 9.0 or less and 5.5 or more and the increasing the pH of the aqueous calcium carbonate dispersion are repeated.