Theoretical and mechanistic insights into control factor-assisted CO2 mineralization with olivine

Abstract

We elucidate the CO2 mineralization mechanism with Mg-rich forsterite via theoretical approach including density functional theory (DFT) calculations and molecular dynamics (MD) simulations. Here, the CO2 mineralization follows two steps: the ion dissolution pathway for dissolving Mg ions from the forsterite surface, and the cluster growth pathway, where ion pairs agglomerate into molecular-sized MgCO3 clusters in aqueous solution. Step-by-step reaction mechanism for the dissolution of Mg ion was investigated via DFT calculations, and the formation procedure of solvated magnesite clusters and their structural changes over time were observed through MD simulations. Afterward, the effects of three control factors of pH, temperature, and hetero-metal ions were studied for both pathways. We found that the adjustment of pH contributed to the structural changes of the mineral surface and clustering ion pairs, which in turn affected the kinetics of reaction pathway. Also, high-temperature condition induced positive effects for accelerating both mineralization pathways. Lastly, calcium and ferrous ions showed opposite effects, promoting and hindering the overall processes, respectively. Importantly, our mechanistic study suggests that the pH of the solution changes alternatively between acid and base conditions during each mineralization pathway and pH condition induced by the preceding mineralization pathway facilitates the subsequent one. (c) 2023 The Korean Society of Industrial and Engineering Chemistry. Published by Elsevier B.V. All rights reserved.