Butanediol-assisted direct carbonation of gypsum in ammonia solution at ambient temperature: Influence of process parameters on CO2 capture

This research aimed to optimize the mineral carbonation of gypsum in the presence of butanediol (BUD) to enhance carbon dioxide capture efficiency, and suppress ammonia desorption from the reactive mixture. The influence of the investigated parameters on the characteristics of the obtained calcium carbonate-rich particles was also examined. Previous studies have demonstrated that BUD enhances CO 2 absorption and reduces ammonia volatilization. The carbonation reaction was conducted in a batch reactor under atmospheric pressure and ambient temperature, minimizing operational costs. The investigated parameters included the NH₃:Ca molar ratio, stirring speed, and BUD concentration. The CO 2 concentration in the inlet gas stream (15 % v/v) was selected to simulate typical post-combustion flue gas conditions. During the reaction, the pH of the mixture, CO 2 concentration, and ammonia concentration in the exhaust gas were continuously monitored. Based on the experimental data, the CO 2 absorption efficiency, ammonia desorption rate, and CaCO 3 content in the final product were determined. The optimal values achieved were: CO 2 absorption efficiency of 84.56 %, ammonia desorption inhibition efficiency of 50.00 %, and CaCO 3 content of 88.49 %. Additionally, the highest vaterite content in the CaCO 3 powder reached 86.99 %. The specific surface area of the CaCO 3 powder peaked at 5.18 m²/g, with a pore volume of 0.000346 m³ /g. All tested parameters remarkably influenced CO 2 absorption, ammonia desorption inhibition, and CaCO 3 concentration in the product (p-values < 0.05), except for stirring speed, which did not significantly affect CO₂ absorption (p > 0.05). • Direct carbonation of gypsum in ammonia solution was enhanced by adding butanediol. • The process runs at ambient pressure and temperature, reducing energy demand. • Under optimal conditions, CO 2 capture efficiency increased by 30 %, reaching 85 %. • High gypsum conversion and high CO 2 capture were achieved simultaneously.