Water reactivity in the liquid and supercritical CO₂ phase: Has half the story been neglected?

Aqueous-phase mediated chemical reactions with dissolved CO₂ have long been considered the principal if not only reactive process supporting mineralization reactions with basalt and other reactive reservoir rocks and caprocks in deep geologic sequestration systems. This is not surprising given the quite high solubility of CO₂ in the aqueous phase and ample evidence from natural systems of the reactivity of CO₂charged waters with a variety of silicate minerals. In contrast, comparatively scant attention has been directed at reactivity of water solvated in liquid and supercritical CO₂, with the exception of interest in the impacts of water in CO₂ on the corrosion of pipeline steels. The results presented in this paper show that the most interesting and important aspects of water reactivity with metal and oxide surfaces of interest in geologic sequestration systems actually occurs in the liquid or supercritical CO₂ phase.