Enhanced sequestration of CO₂ from simulated electrolytic aluminum flue gas by modified red mud

The aluminum industry is facing severe economic and environmental problems due to increasing carbon emissions and growing stockpiles of red mud (RM). RM is a strongly alkaline, high-emission solid waste from the alumina industry with potential for CO₂ sequestration. However, the effectiveness of RM carbon sequestration is poor, and the mechanism behind it is not well understood. In this study, the effect of microwave and tube furnace activation of RM on CO₂ sequestration in alumina was first investigated at different temperatures. The result showed that the CO₂ sequestration capacity of unmodified RM (URM) was only 14.35 mg/g at ambient temperature and pressure, and the CO₂ sequestration capacity could be increased to 52.89 mg/g after high-temperature activation and modification. Besides, high-temperature activation and modification will effectively improve the carbon sequestration capacity of RM. The carbonized RM was characterized by FT-IR, SEM, XRD, laser particle size, TG-DSC, and pH measurements. In addition, the mechanism of RM capturing CO₂ was also proposed, which shows that CO₂ was finally sequestered in the RM as CaCO₃. The change in particle size distribution and the mineral phase in the RM indicated that high-temperature activation modification positively affects the application of RM to the sequestration of CO₂. This study can provide a promising technology for the low-carbon and green development of the aluminum industry, as well as achieving the waste treatment and utilization objective.