PARAMETRIC ANALYSIS OF CO2-MINERALIZATION POTENTIAL OF SILICATE MINERALS FOR OPTIMIZING CARBONATION EFFICIENCY UNDER IN-SITU AND EX-SITU CONDITIONS

As greenhouse gas emissions continue accelerating global warming, innovative and long-term solutions are urgently needed to ensure our planet's sustainability. Carbon capture, utilization, and storage (CCUS) technologies have emerged as critical tools for curbing emissions and achieving net-zero carbon goals by 2050. While conventional CCUS focuses on injecting CO₂-rich brine into saline aquifers, CO₂ mineralization in mafic rocks presents an effective and permanent alternative. By harnessing the natural reactivity of Ca, Mg, and Fe-rich minerals in CO₂-rich fluids, this approach locks carbon into solid carbonates, providing a durable and scalable solution for carbon storage.

This study explores the effects of depth (pressure-temperature), CO₂ fugacity (pCO₂), and reactive surface area (SA) as a function of fracture surface roughness on mineral carbonation potential in mafic ore deposits using the reactive-transport modeling. Using a 1 m³ mixed-flow batch reactor model with a single mineral and parallel-plate fractures, we simulated mineral dissolution (forsterite, diopside, or anorthite) under kinetic constraints and precipitation of magnesite and/or calcite under local equilibrium. For each mineral, we ran 1100 scenarios for 1000 years with unique combinations of depths (P-T), pCO₂, and SA, representing surface and deep conditions.

Response surface analysis of carbonation potential (α_mineral = g CO₂ mineralized/g initial silicate) showed that at surface conditions, α_mineral is more sensitive to SA than pCO₂. However, with depth, the sensitivity of α_mineral on pCO₂ increases. Thus, under subcritical pCO₂ conditions (< 500 m depth), the most fractured mafic rock shows the highest α_mineral. Increasing depth enhances α_mineral due to higher CO₂ solubility, promoting more silicate dissolution and carbonate precipitation. Comparison between minerals showed α_Forsterite > α_Diopside > α_Anorthite, with forsterite driving the initial rapid carbonation in a complex rock, while diopside and anorthite continue to mineralize slowly for a prolonged period, providing a long-term CO₂ storage solution. These findings support building predictive frameworks for selecting optimal feedstocks and maximizing CO₂ mineralization in mafic ore bodies and mine tailings.