Influence of Thermal Treatment Applied to Fe(III) Polyhydroxy Cation Intercalated Vermiculite on the Adsorption of Atrazine

Intercalation of vermiculite with Fe(III) polyhydroxy cations at 1:1 and 2:1 [OH-]/[Fe(III)] molar ratios increases the affinity of the clay mineral toward atrazine in comparison with potassium saturated vermiculite. The present paper describes the effects of thermal treatments applied to Fe(III) polyhydroxy cations modified vermiculite on the adsorption properties of the clay mineral. Only small changes in the textural characteristics were observed for the materials intercalated with either 1:1 or 2:1 [OH-]/[Fe(III)] molar ratios treated at 100 and 250 °C. In comparison with potassium saturated vermiculite, or intercalated vermiculite treated at 100 °C, a significant enhancement in the adsorption of atrazine was observed for the materials treated at 250 and 400 °C, which removed more than 95.8 and 99.5% of the herbicide initially present in a 50.0 μg L-1 aqueous solution, respectively. In comparison with potassium saturated vermiculite and intercalated vermiculite treated at 100 °C, a lower desorption degree of preadsorbed atrazine was observed for both intercalated materials treated at 250 and 400 °C. These findings suggest that the thermal treatment produced modified vermiculite materials with a high adsorption capacity and high affinity toward atrazine, with potential application in the removal of this herbicide, as well as other triazines, from aqueous medium. Keywords: Clay minerals; intercalation; herbicide; adsorption