Evaluation on direct aqueous carbonation of industrial/mining solid wastes for CO2 mineralization

Carbonation of industrial alkaline resources can achieve dual effects of CO2 sequestration and solid waste management, and the carbonated product may act as a potential cementitious backfill material. Based on this idea, CO2 mineralization characteristics and potential of typical industrial solid wastes, mine tailings and their mixtures are investigated by direct aqueous carbonation, and effects of reaction parameters, including particle size, reaction temperature, solid-to-liquid ratio, CO2 concentration, are systematically explored. Results show that industrial solid wastes with a high Ca content such as carbide slag have better carbonation activity with the maximum CO2 sequestration capacity of 544.6 g-CO2/kg, while the carbonation of mine tailings is very weak. The combination of coal fly ash with tailings has a potential stimulative effect during carbonation. Moreover, influences of carbonation parameters are revealed in this study, and optimal reaction parameters are determined to be particle size below 75 μm, temperature of 60 °C, solid-to-liquid ratio of 100 g/L, and CO2 concentration of 15% within mild range. These results can provide fundamental knowledge for the integrated CO2 mineralization and goaf backfilling, and accelerate carbon reduction and waste resource utilization.