CO₂ mineralization through local cement dust: A sustainable sequestration pathway

Carbon dioxide (CO₂) sequestration via mineralization is an efficient approach to permanently store this greenhouse gas in the form of solid carbonates. Moreover, annually increasing stocks and expensive landfills of cement kiln dust (CKD) necessitate groundbreaking solutions to utilize this CKD. One way to simultaneously utilize CKD and sequester CO₂ is CKD aqueous mineralization. This work explored CKD carbonation at various liquid to solid ratios (0.4–10), mineralization times (10–120 min), mineralization temperatures (25–75°C), and CO₂ flow rates (5–20 ml/min). The product analysis using thermogravimetric analysis (TGA), X-ray diffraction analysis (XRD), and scanning electron microscopy (SEM) was conducted to identify CO₂ governing mineralogical and chemical processes. The product characterizations revealed that an increase in liquid to solid ration from 0.4 to 10 facilitated higher CO₂ uptake and yielded calcite as major product that was further confirmed by XRD and SEM. An increase in mineralization time from 10 to 20 min improved CO₂ uptake, however, further increase in time even up to 120 min had no significant impact on CO₂ uptake. The product analysis indicated no influence of mineralization time on polymorph of calcite formed. An increment in mineralization temperature from 25 to 50°C produced more carbonated products (increased CO₂ uptake), however a further increase in temperature to 75°C showed a decrease in CO₂ uptake. The product morphology remained independent of mineralization temperature. The impact of CO₂ flow rate demonstrated that both the product yield (CO₂ uptake) and product morphology were insignificantly affected by change in CO₂ flow rates. These findings elucidate the CO₂ mineralization processes of CKD and are vital to explore CO₂ sequestration by CKD.