The effect of butanediol on the characteristics of calcium carbonate produced by direct mineral carbonation from gypsum in ammonia solution

Mineral carbonation is a process in which carbon dioxide reacts with various natural or synthetic minerals to form stable carbonates, making it a promising method for CO 2 sequestration. In this study, an ammonia solution was used as an absorption promoter, while gypsum served as the calcium source. A key challenge in the mineral carbonation of gypsum in alkaline ammonia solutions is the reduced solubility of gypsum. Moreover, the process depends on CO 2 absorption and its subsequent reaction with calcium ions. To address these challenges, 1,4-butanediol (BUD) was proposed as an organic additive to enhance the mineral carbonation of gypsum. The research focused mainly on the effect of BUD on the CO 2 sequestration efficiency and the characteristics of the precipitated powder. Experiments were done at 1,4-butanediol concentrations in the 0.0 - 0.5 mol/dm 3 range. The synthesized powders were characterized by thermogravimetric analysis (TGA), X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), surface area measurement, particle size distribution, and scanning electron microscopy (SEM). It was shown that the presence of BUD improved the CO 2 sequestration efficiency in the studied system. Moreover, when the concentration of BUD increased, the calcium carbonate concentration rose to 83%, and the vaterite content obtained from calcium carbonate increased to 90%. The calcium carbonate-rich powder contained mainly spherical vaterite particles, and the surface area and average particle size increased with the increased amounts of BUD. • 1,4-Butanediol supports direct mineral carbonation of gypsum in ammonia solution • Process enables CO 2 sequestration and gypsum waste valorization under mild conditions • 1,4-Butanediol significantly enhances CO 2 sequestration efficiency • Higher 1,4-butanediol concentration resulted in a higher gypsum conversion • Used diol promotes formation of vaterite particles with increased surface area