Modeling and response surface methodology optimization of reaction parameters for aqueous mineral carbonation by steel slag

CO2 sequestration via mineralization of steel slag has received widespread attention due to its ability to achieve in -situ CO2 sequestration in steel industries and high -value utilization of steel slag. The final CO2 sequestration capacity of steel slag is closely related to the reaction parameters (i.e., reaction duration, reaction temperature, CO2 vol concentration, and liquid -solid ratios) of mineralization. The reaction parameters may have synergistic effects on the ability of steel slag to sequestrate CO2 . Therefore, the single -factor (one -factor -at -a -time) experimental strategy can't obtain optimal process parameters. Herein, response surface methodology and the Box-Behnken Design were employed in determining optimal conditions. It is found that the combined effects of CO2 concentration in combination with reaction temperature and liquid -solid ratio significantly influence the sequestration process ( P = 0.0082 and P < 0.0001, respectively). Conversely, the combined effects of reaction duration with liquid -solid ratio and CO2 concentration were found to be less significant ( P = 0.6905 and P = 0.6114, respectively). The reasons behind this observation can be ascribed to the focus of this research on the later stages of the reaction, during which it proceeds smoothly. Additionally, alterations in temperature, liquid -solid ratio, and CO2 concentration not only affect the initial pH, CO2 dissolution rate and quantity, and reaction kinetics but also alter the patterns of their collective impact on CO2 sequestration. The CO2 capture could reach 179.1 g-CO2 /kg-steel slag at the optimal condition (i.e., 56.14 degrees C reaction temperature, 6.66 ml/g liquid -solid ratio, 44.53 wt.% CO2 concentration, and 286.73 mins reaction time), compared to single -factor stepwise optimization, which improves by about 9.84 %. Implementing this optimized mineralization process could enable the Chinese steel industry to capture an estimated 27.4 million tons of CO2 annually, based on an annual production of 153 million tons of steel slag.