Study of the thermal decomposition of a sepiolite by mid- and near-infrared spectroscopies

Near-infrared (NIR) and mid-infrared (MIR) spectroscopies were used to characterize the hydroxyl groups present in a sepiolite and its calcination products at 250, 500 and 800 °C. Calcining the sepiolite at 250 °C was found to result in its dehydration through the loss of coordination water. Raising the calcination temperature to 500 °C caused the sepiolite structure to fold and hydroxyl groups in octahedral layers to be removed. Finally, calcination at 800 °C resulted in a phase change leading to enstatite, as confirmed by XRD spectroscopy.

Graphical abstractNIR spectral region (7800–6200 cm−1) for sepiolite and its calcination products: (a) SEP; (b) SEP-250; (c) SEP-500 y and (d) SEP-800.Figure optionsDownload full-size imageDownload as PowerPoint slide