Stabilization of nesquehonite for application in carbon capture utilization and storage†

Abstract

Nesquehonite (MgCO₃·3H₂O) is of interest as a carbon sink for mineral carbonation as its formation is kinetically favored at ambient temperatures and pressures and offers the highest CO₂ : MgO ratio compared to most other hydrated magnesium carbonates (HMCs). However, the phase tends to convert to more stable HMCs depending on the environment and time leading to long-term instability. Here, we report a successful attempt to stabilize nesquehonite using a phosphate-based pH 7 buffer, while controlling the equilibrium of aqueous carbonate species did not stabilize the phase. Phosphate interacts with nesquehonite to form a Mg-phosphate phase on nesquehonite's surface. We suggest that a protective layer is formed, which prevents further transformation of nesquehonite.