Thermal decomposition process of dypingite Mg5(CO3)4(OH)2·5H2O

Abstract

Dypingite is one of the most common phases of crystalline magnesium carbonate hydrates, which are considered potential targets for CO2 mineral sequestration. Ex-situ high-temperature X-ray diffraction and ex-situ high-temperature synchrotron X-ray scattering experiments with pair distribution function analysis were used to explore the thermal transformation process of dypingite. Dypingite transformed to hydromagnesite until 100 °C, but its local structure remained unchanged. At the temperature range from 250 °C to 350 °C, where the amorphous phase was predominant, the second and third coordination spheres were continuously modified and crystallized to MgO at 400 °C. Although the local structure of dypingite was as that of hydromagnesite, dypingite exhibited a different thermal transformation pathway from hydromagnesite.