Formation and Dissolution of Surface Metal Carbonate Complexes: Implications for Interfacial Carbon Mineralization in Metal Silicates

Abstract

Rapid CO 2 mineralization in natural and synthetic metal silicates provides a potentially scalable solution to address the untethered global carbon emissions. When metal silicates react with humidified CO 2 -rich fluids, a nanometer-thick water film adsorbs on mineral surfaces. Experiments show that such nanoscale reactive environments demonstrate an enhanced level of carbonic acid formation, metal-(bi)carbonate surface complexation, and fast carbon mineralization. Hindered by the spatiotemporal complexities of in situ measurements at the solid−liquid interface, the mechanistic picture of carbon mineralization mechanisms in water films remain obscure. Here, we leverage reactive and nonreactive molecular simulations to probe the elementary reaction steps involved in the interaction of bicarbonate with metal silicate surfaces. We observe that a reverse proton transport between the bicarbonate and surface hydroxides drives carbonate production and surface metal carbonate complexation in agreement with in situ spectroscopy measurements. The resultant carbonate can also contribute to the ligand-enhanced dissolution that appears to be slightly favorable over carbonate-unassisted dissolution. We also discuss the potential implications of metal carbonate complex formation and dissolution on lowering the growth's configurational entropy penalty and the rise of interfacial carbon mineralization pathways.

Emerging investigator series: kinetics of diopside reactivity for carbon mineralization in mafic–ultramafic rocks

“…Such surface complexations can lead to proton-or ligand-promoted dissolution. [117][118][119][120][121][122]…”

The Future of CO2 Geological Sequestration: An Overview of Mineralization in Aqueous and Supercritical States

“…The Microprocess of Wet scCO 2 Mineralization. The adsorption−complexation process is widely accepted for the microprocess of wet scCO 2 mineralization, 50 as shown in Figure 5. In this process, the water dissolved in scCO 2 forms a thin water film of only a few nanometers thick on the mineral surface (a).…”

“…Mineralization microprocesses in CO 2 aqueous solution (Adapted with permission from ref . Copyright 2023 American Chemical Society).…”

A ReaxFF Potential for Modeling Organic Matter Degradation with Oxybromine Oxidants

“…Extending the notion of bond order parameters in modeling covalent systems, [24] reactive force fields, such as ReaxFF [25] and AIREBO, [26] provide a classical compromise with DFT-level accuracy and accelerate calculations by orders of magnitude. Properly parameterized ReaxFF potentials can simulate chemical reactions at the solid, liquid, and gas interfaces and these potentials have already advanced our understanding of a range of complex geochemical reactions from interfacial carbon mineralization [27][28][29] to the maturation of organic matter. [30,31] Previously, we developed an H/C/O/Cl ReaxFF potential [32] to model the oxidation of organic matter with oxychlorine reagents, which remain limited to very low pH due to the absence of alkaline or earth alkaline cations in the parameter set to balance the charged reactive fluid.…”