Increased thermal stability of nesquehonite (MgCO3·3H2O) in the presence of humidity and CO2: Implications for low-temperature CO2 storage

Nesquehonite thermal stability was clearly enhanced under humid conditions for short-term (<20 h) in situ X-ray diffraction and thermogravimetric experiments. Formation of hydrous surface layers may impede structural H2O release from nesquehonite; delaying dehydration and preventing subsequent decomposition. Enhanced stability of nesquehonite was also observed under a CO2 atmosphere. This study presents novel insights into the importance of temperature, pH2O and pCO2 when considering the suitability of nesquehonite as a long-term CO2 store. Additionally, it establishes basic, previously overlooked conditions that are essential considerations when tailoring disposal, storage and ex situ carbonation to enhance CO2 stability in metastable Mg-carbonate phases.