Insight into the direct carbonation process of Ca2SiO4 based on ReaxFF MD simulation and experiments

Abstract

Ca₂SiO₄ is the primary carbonation-reactive mineral in steel slag, and demonstrates significant carbon sequestration potential, yet its microscopic reaction processes remain unclear. This study investigated the carbonation behavior of Ca₂SiO₄ using ReaxFF MD simulations. The results indicated that as CO₂ concentration increased, the capture rate of Ca₂SiO₄ decreased, and the molecular structure of the resulting CaCO₃ varied in oxygen origin. At room temperature, the carbonation rate of Ca₂SiO₄ gradually decreased over time until it reached equilibrium. Increasing the temperature could reactivate the carbonation, but the rate would still decline until it reached equilibrium again. Higher temperatures could accelerate the formation of the intermediate C₂O₅²⁻ and internal CO₃²⁻ diffusion, thereby boosting the carbonation and increasing CO₂ adsorption. This study investigated the carbonation of Ca₂SiO₄ at the atomic level, aiming to link microscopic molecular processes with macroscopic experimental phenomena, thereby providing a theoretical foundation for enhancing the carbonation efficiency of steel slag.