Replacement reactions for carbon geosequestration may be faster in calcium olivine vs magnesium olivine

Abstract

AbstractCO2 mineralization is the safest CO2 geosequestration method with the highest sequestration capacity. Even though there have been lab and pilot-scale demonstrations, the complex chemical reaction is still elusive at atomic level. Here, I show that the ab initio molecular dynamics (AIMD) and metadynamics simulations enable quantitative analysis of reaction pathways, thermodynamics, and kinetics of the Mg2+ and Ca2+ ion dissolutions from olivine minerals, which have high weathering potential for carbonation process. The leaching of Ca2+ from the Ca-olivine surface is a ligand exchange process that results in a much lower energy barrier with 103 times faster dissolution rate compared to the leaching of Mg2+, which the tight magnesium sites on the forsterite (Mg-olivine) surface forbid ligand exchange. These results provide indication on water capabilities in solvating Ca2+ and Mg2+ that are relevant to mineral carbonation and can help the evaluation of potential enhanced CO2 mineralization mechanisms.