The physico-chemical characterization of Tunisian bentonitic clays is based on the determination of the mineralogical composition (X–ray diffractions and infrared spectroscopy), chemical analysis, cation exchange capacities and the total surface area. The result given by these techniques show that these samples were smectic clay of beidellitic character. In the other hand, the activation of these clays by hydrochloric acid shows an increase of the specific surface area and favorite the clarification of vegetable oils.