Study of raw and thermally treated sepiolite from the Mantoudi area, Euboea, Greece

Raw and thermally treated sepiolites from the Mantoudi area, Euboea, Greece, were investigated by means of X-ray diffraction (XRD) in combination with thermo-gravimetric analysis (TG/DTG) and differential thermal analysis (DTA), as well as Fourier transform (FTIR) spectroscopy, in order to study the collapse of the sepiolite structure with increasing temperature. The main mineral constituent (> 95%) is a well crystallized sepiolite. Quartz and dolomite occur in minor amounts. Calcination of the samples was carried out up to 350, 720 and 820 degrees C, for 2 h, and 'sepiolite dihydrite', 'sepiolite anhydrite' and 'enstatite' were formed, respectively, as magnesium co-ordinated water and octahedrically co-ordinated hydroxyl groups, are removed and the dehydroxylated phase recrystallize to enstatite (MgSiO3). These structural and textural changes play an important role to the properties and uses of the studied sepiolites.