Glycine-Induced Synthesis of Vaterite via Direct Aqueous Mineral Carbonation of Flue Gas Desulfurization Gypsum

Mineral carbonation of flue gas desulfurization gypsum (FGDG) can not only sequester CO2 to mitigate the greenhouse effect, but also produce CaCO3 to generate economic benefit. A mixture of calcite and vaterite CaCO3 was produced by FGDG carbonation in our previous study. Nevertheless, the production of uniform crystalline CaCO3, especially for vaterite, still maintains a big challenge via carbonation of FGDG. Herein, nearly pure vaterite was synthesized via FGDG carbonation in the presence of glycine was reported firstly. The results show that the content of vaterite increased from 60% to 97% with increasing glycine concentration and then kept a constant value, indicating that glycine can promote the formation of vaterite and inhibit the growth of calcite. Additionally, the investigation of vaterite growth mechanism in the presence of glycine demonstrated that the formation of intermediate, glycinate calcium, played an important role to stimulate the growth of vaterite. This study provides a new insight to produce a high-valued vaterite CaCO3 during the direct mineral carbonation of FGDG.