CO₂ capture by accelerated carbonation of alkaline wastes: A review on its principles and applications

CO₂ capture, utilization, and storage (CCUS) is a promising technology wherein CO₂ is captured and stored in solid form for further utilization instead of being released into the atmosphere in high concentrations. Under this framework, a new process called accelerated carbonation has been widely researched and developed. In this process, alkaline materials are reacted with high-purity CO₂ in the presence of moisture to accelerate the reaction to a timescale of a few minutes or hours. The feedstock for accelerated carbonation includes natural silicate-minerals (e.g., wollastonite, serpentine, and olivine) and industrial residues (e.g., steelmaking slag, municipal solid waste incinerator (MSWI) ash, and air pollution control (APC) residues). This research article focuses on carbonation technologies that use industrial alkaline wastes, such as steelmaking slags and metalworking wastewater. The carbonation of alkaline solid waste has been shown to be an effective way to capture CO₂ and to eliminate the contents of Ca(OH)₂ in solid residues, thus improving the durability of concrete blended with the carbonated residues. However, the operating conditions must be further studied for both the economic viability of the technology and the optimal conditions for CO₂ reaction.