Effects of Heating and Acid Activation on the Structure and Surface Properties of a Kaolinite-illite-smectite Clayey Mixture

Abstract

This work aims at studying the effects of heat treatment and acid activation on the surface properties of a mixture of kaolinite-illite-smectite clay minerals collected from North Est of Tunisia. The raw material was characterized by various analytical and spectroscopic techniques such as XRD, FT-IR, TG-DSC, and N 2 physical adsorption. The true density of starting raw material increased from 2580 to 2609 kg.m 3 , while the surface area, S BET , decreased from 70.7 to 35.3 m 2 .g-1 upon heat treating at 550°C for 1 h. Acid activation of heat treated material led to partial dissolution of the octahedral sheets by interlayer and edge attack, the formation of amorphous silica and an overall structural degradation. Dynamic vapour Sorption (DVS) measurement revealed that the surface energy of the system increased after acid activation and with the acid treatment time. These structural/surface changes translated in higher negative zeta potential (