Structural Evolution of Olivine during Mechanochemically Assisted Mineral Carbonation under CO2 Flow

The mechanism of the mechanically assisted mineral carbonation of commercial olivine under the flow of a carbon dioxide (CO2)/nitrogen (N2) mixture has been elucidated by ex situ powder X-ray diffraction and Fourier-transform infrared spectroscopy. The overall CO2 conversion depends on the rotational frequency of the mill's engine, and it reaches 85% within 90 min of mechanical treatment at a flow rate of 2.5 L min-1. By tuning the frequency of rotation, the kinetics of CO2 conversion unveil a complex reaction pathway involving subsequent steps. Structural analyses suggest that clinochlore, a magnesium (Mg-)- and iron (Fe-)-containing aluminosilicate gathered among the components of olivine, is formed and consumed in different stages, thus promoting the CO2 sequestration that eventually results in the formation of hydrated and anhydrous Mg-based carbonates.