Lysine-coupled fly ash accelerated CO2 mineralization: Feasibility and reaction mechanism

CO2 mineralization using alkaline solid waste is a promising technology for integrated pollution reduction and carbon sequestration. This paper proposed an efficient and environmentally friendly method for lysine-coupled fly ash accelerated CO2 mineralization. And the feasibility of this process was preliminarily explored. The results showed that under mild operating conditions, the promotion of lysine achieved a carbon sequestration capacity of approximately 122.60 g-CO2/kg-FA, with a CO2 mineralization efficiency of 72.84 %. Additionally, lysine acted as a crystal form regulator for CaCO3, resulting in vaterite CaCO3 at an appropriate lysine concentration. Using 13C nuclear magnetic resonance (NMR), the carbamates, bicarbonates/carbonates, and Lys/protonated Lys at different reaction stages were considered to propose a novel reaction mechanism for the Lys-FA-H2O-CO2 system. It indicates that lysine accelerates key reaction steps in the fly ash carbonation process. Lysine, acting as a proton acceptor and promoting carbamate formation, accelerates the mass transfer of CO2 from the gas phase to the liquid phase. Meanwhile, the presence of lysine enhances the leaching capacity of Ca2+ by three times compared to H2O.