Preparation of high surface area CaCO3 by bubbling CO2 in aqueous suspensions of Ca(OH)2: Effects of (NaPO3)6, Na5P3O10, and Na3PO4 additives

CaCO3 with a high surface area (50–73 m2/g) and pore volume was prepared by bubbling CO2 into a suspension of Ca(OH)2 (2.4 wt.%) with the addition of a small amount (≤ 0.2 wt.%) of one of the additives: (NaPO3)6, Na5P3O10, and Na3PO4. The surface area was markedly affected by the solution pH when the additive was added and the amount added. The effect of an additive in raising the CaCO3 surface area was to produce loose aggregations of fine primary particles. The additive should be added after bubbling CO2 into the Ca(OH)2 suspension, and there was an optimal concentration of the additive (≤ 0.2 wt.%) for maximizing the surface area. Among the three additives tested, (NaPO3)6 and Na5P3O10 were better than Na3PO4. The high surface area CaCO3 was highly reactive toward SO2.