High-gravity Reactive Precipitation Process and Morphology Control for Precipitated Calcium Carbonate
超重力反应沉淀法制备碳酸钙的过程与形态控制

Electrical conductivity, pH, and X-ray diffraction measurements were used to investigate the carbonation process and kinetics, of calcium carbonate synthesized using the high-gravity reactive precipitation process. Carbon dioxide adsorption was found to be the rate-controlling step during the initial stage of the carbonation process. In the later stage of the carbonation process, the rate controlling step was changed to dissolution of Ca(OH)2. In addition, gelation occurred during the initial stage of the carbonation process, and marked changes in pH and electrical conductivity were observed in this period. XRD study on the intermediate product formed during this period exhibited unique crystal structure. As a result of the augmented CO2 mass transfer rate and the intensified micro-mixing under high-gravity environment, the time required for the carbonation process has reduced by 4 times as compared to the conventional carbonation process. The precipitated calcium carbonate with different sizes and shapes (cubic, chain, needle, flake, spindle, sphere, rosette and fiber) were synthesized by means of using different operating conditions and selecting different additives to control the nucleation and the growth of the calcium carbonate.