CO2 mineralization characteristics of Ca2+-rich leachate from desulfurization gypsum and the regulation of CaCO3 crystal and morphology

It is very promising that Ca-rich solid wastes could act as calcium source to convert CO₂ from industrials into functional CaCO₃ product via aqueous carbonation reaction. Because of the complexity in chemical components and mineral classifications of solid wastes, there is still a big challenge for any one solid waste that how to obtain highly pure CaCO₃ with a certain crystal form, size and morphology through regulating mineralization process parameters or using inorganic /organic additives. This work aimed to evaluate the potential for indirect CO₂ mineralization of Ca²⁺-rich leachate from desulfurized gypsum (DG) which was produced from wet limestone-gypsum desulfurization system in a coal-fired power plant. The effects of different parameters on Ca²⁺ leaching characteristic of gypsum and the CO₂ mineralization behavior of Ca²⁺-rich leachate was investigated in detail, as well as the regulation of three additives and reaction conditions onto crystal form and morphology of CaCO₃ products. The results showed that the leaching efficiency of Ca²⁺ from gypsum could reach up to about 46 % at the optimal leaching parameter. Under the optimal operating carbonation parameters, the mineralization efficiency of desulfurized gypsum reached 22 % and the corresponding mineralization capacity was 56.15 kg∙CO₂/t∙DG. The addition of ethylene glycol and sucrose promoted the formation of vaterite, while the creation of pine-like aragonite was more favored in the presence of magnesium chloride.