Effects of Carbon Sources and Nucleating Agent on the Precipitation Reaction of Indirect Carbonation

Indirect mineral carbonation is considered an ideal CO 2  sequestration strategy because of its high carbonation rate and high value-added products. This research explores the carbonation ability of different carbon species—CO 3 2– ions, HCO 3 – ions, and H 2 CO 3 —in their dominant region. When (NH 4 ) 2 CO 3 was used as the carbon source, the Ca 2+ ions carbonation rate was hardly affected by pH, while NH 4 HCO 3 was the opposite. When the pH of the leachate decreased from 8.67 to 6.20, the carbonation rate of (NH 4 ) 2 CO 3 decreased from 99.32% to 98.42%, while the carbonation rate of NH 4 HCO 3 decreased from 96.28% to 37.71%. Meanwhile, this research also probed the influence of the nucleating agent on the carbonation rate and carbonation products. The addition of nucleating agent can increase the carbonation rate. For a CH 3 COOH concentration of 0.6 M for mixed leaching, the carbonation rate was increased by 26.81% with the addition of nucleating agent. Meanwhile, the nucleating agent can also induce the growth of CaCO 3  toward the crystal form of the nucleating agent itself. When (NH 4 ) 2 CO 3  and NH 4 HCO 3  were used as the carbon sources, CaCO 3  mainly exists in the crystal form of vaterite, and after adding the nucleating agent, the crystal form changes to calcite.