Preparation of CaCO^sub 3^ nanoparticles in a surface-aerated tank stirred by a long-short blades agitator

In this work, a novel long-short blades agitator was used to intensify the mass transfer process in the Ca(OH)2-H2O-CO2 system for the preparation of CaCO3 nanoparticles. CO2 was entrained into the liquid through surface aeration in a 10 L stirred tank. Very uniform CaCO3 nanoparticles with the mean size of 24–110 nm were obtained. The prepared particles are calcite crystals. The mass transfer of the precipitation process has also been analyzed. The gas-liquid interfacial area was measured by using the transport-reaction equations. The influences of the rotating speed of the agitator, the reaction temperature, the volume fraction of CO2 in the gas phase, and the initial concentration of Ca(OH)2, on the mean size, the particle size distribution, and the reaction time were discussed. Compared with other carbonation methods, this work provides an easy-operation and high-efficiency method for preparing uniform CaCO3 nanoparticles with low risk of equipment blockage.