Carbon capture, utilization, and storage (CCUS) technologies are central to mitigating greenhouse gas emissions and achieving net-zero emission goals. Among these, CO2 mineralization in mafic and ultramafic rocks offers a permanent storage mechanism by converting CO2 into stable carbonates through reactions with Ca-, Mg-, and Fe-rich minerals. This study examines the effects of depth-pressure-temperature (P-T), CO2 fugacity (pCO2), CO2 saturation, reactive surface area (SA), and fracture surface roughness on mineral carbonation potential in mafic deposits, utilizing reactive-transport modeling. Using a 1 m3 mixed-flow homogeneous reactor with parallel-plate fractures, we conducted 4400 single-mineral simulations (forsterite, diopside, anorthite, and magnetite) over 1000 years, with variable depth, pCO2, and SA. Additional simulations examined carbonation in synthetic heterogeneous mixtures representing mafic intrusions from the Duluth Complex, Minnesota. Response surface analysis of carbonation potential (₌₈₍₄ₑ₀₋=g CO2 mineralized/g initial mineral) showed higher sensitivity to SA than pCO2 at the surface, with rougher surfaces yielding higher ₌₈₍₄ₑ₀₋. At constant SA, the ₌₈₍₄ₑ₀₋ sensitivity to pCO2 increases with depth due to enhanced CO2 solubility at higher P-T, promoting more carbonation. Thus, under subcritical pCO2 (< 500 m), highly fractured mafic rocks exhibited the greatest ₌₈₍₄ₑ₀₋. Forsterite and magnetite showed the highest carbonation (0. 1–0. 65 and 0. 05–0. 45), while diopside and anorthite showed intermediate (0. 006–0. 13) and low values (0. 0012–0. 0046), respectively. Comparison showed that forsterite and magnetite drove rapid carbonation initially, while diopside and anorthite sustained long-term mineralization in complex rocks. These insights advance predictive frameworks for quantifying carbonation potential and optimizing CO2 mineralization conditions in mafic and ultramafic deposits and mine tailings.
Chanda et al. (Fri,) studied this question.