Thermodynamic and Geochemical Simulations of Silicate–CO ₂ –H ₂ O Reactions for Carbon Mineralization

Geochemical reactions among water, CO2, and silicate minerals are fundamental to mineral carbonation, which is a key technological solution for storing anthropogenic CO2. Thermodynamics dictates the feasibility and direction of these reactions under varying geologic conditions. This study utilizes thermodynamic simulations using Python and PHREEQC to model silicate–H2O–CO2 interactions. We quantified Gibbs free energy (ΔrG) and equilibrium constants (K) while accounting for variable molar concentrations of reactants (0.001–1 mol) and temperature ranges (25–200 °C). Results demonstrate that variations in molar concentration can shift ΔrG significantly, causing the same reaction to oscillate between spontaneous and nonspontaneous behavior. Equilibrium constants exhibited extreme variability (10–15–1022) with nonlinear dependencies (power law/exponential) on concentration. Furthermore, simulations indicate that pH and temperature strongly control the saturation indices (SIs) of carbonates; specifically, siderite SI decreases at high temperatures (>100 °C), whereas calcite and dolomite SIs increase. These findings highlight the sensitivity of carbonation efficiency to mineralogical heterogeneity and thermodynamic parameters. The observed nonlinearities suggest that small changes in reservoir composition can drastically alter storage potential, necessitating precise geochemical characterization for optimizing long-term carbon storage strategies.