The Influence of Acid Activation on Surface Characteristics of Natural Bentonite

Bentonite clay is a valuable material in various process industries, thanks to its specific properties. Easy availability, low cost and their effectiveness are the main factors that have made bentonite adsorbent in the edible oil industry. The textural characteristics of bentonite clay play an important role in its performance. In its natural form, as an aluminosilicate material, bentonite does not show satisfactory sorption and catalytic properties, and it needs to be activated. The main goal of this research is to increase the adsorption capacity of bentonite clay by modifying its properties by treatment with organic acid. Activation of bentonite clay in the experimental part was performed with different concentrations of sulfuric acid. The chemical composition of the natural bentonite sample was determined using XRF alongside the influence of acid activation of bentonite with H2SO4 on the surface characteristics (such as specific surface area, pore volume and average pore diameter, adsorption capacity and isotherm type) of bentonite clay. The XRF analysis of the natural bentonite, which contains 56.35% SiO2 and 19.82% Al2O3 as its primary components, confirms that it is an aluminosilicate material. Except for SiO2, which recorded a consistent increase in quantity from 56.35% to 74.15% with increasing acid concentration, the composition of other components, after activation slightly decreased or remained the same.

The acid concentration that yielded the highest increase in specific surface area, as measured by the Brunauer–Emmett–Teller (BET) method, was selected as the optimal concentration for activating bentonite. The specific surface area almost tripled (from 95.519 m2/g to 346.467 m2/g)) by activation with 15% sulfuric acid, with an activation time of 3 hours and a bentonite: acid ratio of 1:5. The research results show the effectiveness of acid modification in terms of improving the characteristics of the porous structure of bentonite samples.