Elucidating Olivine Carbon Mineralization Behaviors under Weakly Acidic to Alkaline Conditions for CO2 Storage.

Olivine ((Mg,Fe)2SiO4), an ultrabasic mineral primarily found in peridotite rock, is earth-abundant and thus has great potential to store anthropogenic CO2 at a scale relevant to climate change mitigation. The groundwater from geologic formations composed of peridotite, such as the Samail Ophiolite in Oman, has an ultrahigh pH (>10), which is underexplored as a direct carbonation condition. This study investigated a wide range of initial pH (3-14) to elucidate the roles of pH and alkalinity during the direct carbonation behavior of olivine at a high temperature (185 °C). Despite the expected negative correlation between pH and olivine dissolution kinetics, this study revealed that alkaline pH conditions significantly enhance direct carbonation kinetics. The study also determined the effects of initial total alkalinity and the roles of different alkalinity sources, offering valuable perspectives for estimating direct carbonation behavior across a wide range of reaction conditions.