Sonochemistry-driven accelerated carbonation of solid wastes: Structural alteration and enhanced CO₂ mineralization

Passivation effect and low mass transfer efficiency are the critical issues limiting the rate and degree of mineral carbonation. In this study, a sonochemistry-driven accelerated carbonation method was adopted by jointly applying ultrasound with aqueous carbonation, aiming at achieving improved carbonation rate and degree while fully activating calcium- and silicate-rich solid waste. Based on the results, ultrasound-intensified carbonation (UC) could reach a maximum carbonation degree of 81.23%, with an increase of 10.16 percentage points relative to the reference group. It also showed a remarkable CO 2 utilization efficiency of 87.13%. More importantly, UC achieved a high carbonation degree within 20 min and promoted more thorough decalcification of Ca-bearing phases. Critically, in the early stage, ultrasonic treatment accelerated CO₂ uptake and carbonation, as reflected by the rapid pH decrease and the higher solid-phase CO₂ utilization efficiency. Ultrasonic treatment also promoted the simultaneous decalcification of hydration products, thereby increasing the concentrations of dissolved ions and the saturation indices of carbonate phases. In the later stage, due to the shear forces and microjets, the particle size was decreased by 81.53% and specific surface area was also 2.11 times that of NC. The passivation layer was eliminated, exposing the Si core. Overall, the proposed UC method provides a significant advancement in the joint fields of CO 2 utilization and waste concrete recycling.