Novel anhydrous unfolded structure by heating of acid pre-treated sepiolite

Acid activation of sepiolite removed the brucitic magnesium octahedral layers, while the tetrahedral sheets formed fibrous and amorphous silica. The coexistence of both structures, sepiolite and free silica after the acid treatment, causes changes in the structural behavior of the sepiolite at elevated temperatures. Whereas, the structure of pristine sepiolite is folded by the elimination of the coordinated water molecules, whereas acid pre-treated sepiolite, remains unfolded after the treatment at 550 °C. Therefore, a novel anhydrous unfolded sepiolite structure with empty and open channels was obtained and characterized by X-ray diffraction and 29Si solid state NMR for the first time.