Thermal and morphological characterisation of organically modified sepiolite

In this paper the study of the morphological and thermal characterisation of pristine and organically modified sepiolites is performed. Sepiolites modified by means of two functionalization processes were studied: adsorption, of quaternary ammonium salts or amines, or grafting of silane reagents. By means of XRD the characteristic diffraction peaks of sepiolite structure were observed in every sample confirming that no structural changes occurred in the mineral lattice upon functionalization. As sepiolite is a non swelling clay organophilization takes place mainly by surface modification, maintaining its crystalline structure. SEM and HRTEM confirmed that the typical acicular morphology of sepiolite was maintained after modification, although the organically modified needles show a more irregular surface pattern. The study of the thermal behaviour of the organically modified sepiolites was performed by thermogravimetric analysis which shows a complex multi-step degradation process due to the overlapping of sepiolite dehydration processes and organic modifier volatilization.