Abstract
This work aims at studying the effects of heat treatment and acid activation on the surface properties of a mix- ture 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 N2 physical adsorption. The true density of starting raw material increased from 2580 to 2609 kg.m 3 , while the surface area, SBET, 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 degrada- tion. Dynamic vapour Sorption (DVS) measurement revealed that the surface energy of the system increased after acid ac- tivation and with the acid treatment time. These structural/surface changes translated in higher negative zeta potential (
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