Abstract: A vermiculite from Beni-Uxera, North Africa, was refluxed with HCl solutions of various concentrations to determine the effect of such a treatment on its surface area. The treated vermiculite was analyzed for “free” SiO2 and by x-ray diffraction, and the refluxing solutions were analyzed for the cations removed from the vermiculite. Surface areas were determined by means of adsorption isotherms of n-butane at 0°C.
The surface area of the acid-treated vermiculite increases with increase in concentration of the acid. Heating of the acid-treated samples or the natural samples decreases the surface area.
The increase in surface area by acid treatment is due to destruction of the vermiculite and its conversion to a “free” form of SiO2 which possesses a large surface area. x-Ray analysis indicated that this “free” SiO2 was not present in the interlayer positions of the crystal lattice of vermiculite.