Kinetic evaluation and applicability analysis on direct aqueous carbonation of industrial/mining solid wastes

CO2 mineralization combined with goaf backfilling is an effective pathway for alkaline solid waste recycling and CO2 emission reduction. Determining the kinetics of solid waste mixtures during direct aqueous carbonation is therefore important. Here, carbonation behavior and kinetics of carbide slag and its mixes with iron tailing are examined using a kinetic model based on the two-film theory. The impact of important operation parameters is assessed through model fitting as well. Results show that there is an excellent fitting accuracy to the carbonation of carbide slag and its 50 % mixtures by the model (average R2 =0.999) although a limitation is observed when the IT blending ratio is very high. Additionally, the change of gas-liquid mass transfer flux is compatible with the theory, and the ideal parameters are determined to be a reaction temperature of 65 degrees C, a solid-liquid ratio of 100 g/L, and a CO2 concentration of 15 %. Difference between the experimental and predicted value is controlled within 10 %. The above results are beneficial to revealing the microscale carbonation mechanism of mixed solid waste and may offer theoretical backing for industrial applications.

Automated summary

CO2 mineralization combined with goaf backfilling is an effective method for alkaline solid waste recycling and CO2 emission reduction. This study focuses on the kinetics of direct aqueous carbonation of carbide slag and its mixtures with iron tailing. A kinetic model based on the two-film theory is used to examine the carbonation behavior, and the impact of operation parameters is assessed. The results provide valuable insights into the microscale carbonation mechanism of mixed solid waste and offer theoretical support for industrial applications.