Study On Preparation And Property Of Nano Calcium Carbonate

Nano calcium carbonate had a variety of morphologies which were prepared and used differently. But the preparation process and properties of nano calcium carbonate were significantly affected by magnesium content in limestone, both Ca2+ and CO32- concentration in carbonation and aging process.Taking MgCO3 in limestone, nucleation promoter and crystal shape modifier as the research object, the effects of them which were about nucleation, growth, coagulation and ripening on preparation and powder property of calcium carbonate, were studied in this paper, with parameters such as reaction rate, conductivity, pH, ion concentration explored.Results showed that MgCO3 in limestone mainly exists in the form of Mg2+ at the end of carbonation reaction, and basic magnesium carbonate microcrystalline particles in powder after activation. Nucleation of calcium carbonate in the early carbonation reaction was promoted while crystal growth was inhibited in the middle of carbonation reaction by Mg2+ in slurry. When magnesium content in slurry was over 1.71%, the average diameter size of calcium carbonate particles decreased, with specific surface area, pH, oil absorption value and saturated moisture absorption rate of powder all increased. When magnesium content was below 1.71%, the influence of magnesium content on preparation of nano calcium carbonate could be ignored.Seed crystal of calcium carbonate was generated after adding nucleation promoter, which enlarged the average size and size distribution of calcium carbonate particles. With the extension of the aging time, the calcium carbonate particles with regular morphology, good dispersion of particle size distribution range could be obtained. When aging time was 3 h, nano calcium carbonate which the average size was 120 nm was obtained with particle size distribution ranging from 100-150 nm.When crystal shape modifier was added, the nucleation and growth rate of calcium carbonate were increased while crystal growth period was prolonged, thus making the particle size large and particle size distribution range widely while particles’coagulation intensified and particles’ dispersion also went bad. With the extension of the aging time, the calcium carbonate particles with regular morphology, good dispersion of particle size distribution range could be obtained. The pH of powder was about 8.2 when aging time was 3 h.