Precipitation of calcium carbonate by carbon dioxide microbubbles

The microbubble generator (MBG)—an apparatus in which tiny micron-sized gas bubbles are produced in the aqueous phase—has been widely used in water purification systems. In this study, the feasibility of utilizing the MBG to precipitate calcium carbonate along the carbonation route was examined. The effects of the calcium hydroxide concentration and the injection flow rate of carbon dioxide on the precipitation process were evaluated. Changes in pH, temperature of the suspension, and residual calcium ion concentration in the suspension were monitored to evaluate the proposed process. In addition, the process was compared with that based on a conventional bubble generator. This revealed a two-fold improvement in the acquisition time required for calcium carbonate precipitation as well as an increase in the conversion efficiency of carbon dioxide to carbonate minerals. The proposed process should be helpful for practical applications of a carbon sequestration method.