Enhanced CO2 sequestration in red mud slurry via ultrasonic pretreatment

Abstract

An ultrasonic pretreatment of red mud (RM) slurry for CO2 sequestration (CS) was studied. Results indicated that untreated red mud (URM) achieved a CS of 29.37 mg/g, whereas, under optimal conditions, the CS of RM slurry after ultrasonic pretreatment (UP) increased to 92.8 mg/g. The mechanisms underlying CS were elucidated: the high efficiency of CS in the RM slurry was attributed to ultrasound facilitating the release of alkaline components from RM, elevating the pH of solution from 10.4 to 12.9. Furthermore, ultrasound facilitated the refinement of RM particles, increasing their contact area with CO2 and thereby significantly improving CS. Through characterization, it was found that the primary carbonated mineral in pretreated RM was katoite, with residual sodalite and cancrinite also present. CO2 ultimately existed as CaCO3 within the aqueous environment and on the RM surface. This work provided meaningful insights into the comprehensive utilization of RM and carbide slag, CO2 mitigation, and sustainable development within the aluminum industry.