In situ high-temperature XRD and FTIR investigation of hohmannite, a water-rich Fe-sulfate, and its decomposition products

The thermal dehydration of hohmannite, Fe2[O(SO4)2]·8H2O, a secondary iron-bearing hydrous sulfate, was investigated by in situ high-temperature X-ray powder diffraction and in situ high-temperature Fourier transform infrared spectroscopy. Combination of the data from both techniques allowed determining the stability fields and reaction paths for this mineral and its high temperature products. Five main dehydration/transformation steps for hohmannite have been identified in the heating range of 25-800 °C. Temperature behavior of the different phases was analyzed, and the heating-induced structural changes are discussed.