Rehydration of heated gibbsite, kaolinite and goethite: An assessment of properties and environmental significance

This study investigated the dehydroxylation of three soil minerals and their rehydration under wet conditions. Rehydroxylation of heated gibbsite was extensive at 95 °C with bayerite and gibbsite forming during 14 days, the process was much slower at 55 °C. Metakaolinite formed from kaolinite and hematite formed from goethite by heating did not recrystallise but did acquire structural water during incubation in water. The specific surface area of all three dehydroxylated minerals was increased substantially by wet incubation. FTIR, conventional and synchrotron XRD and TGA analyses indicate that the dehydroxylated minerals and probably their partly rehydroxylated forms may exist in soils heated by fire, and their presence may affect the chemical behaviour of these soils.