Adsorption of Malathion on Activated Sepiolite from Cyclohexane Solution

Adsorption of malathion on four natural sepiolite samples activated by different combined acid and heat treatments (0.25 N and 0.5 N, HNO3; 110°C and 200°C) from cyclohexane, has been studied. The adsorption isotherms may be classified as H-3 type of the Giles classification which suggests that malathion molecules are strongly adsorbed on the sepiolite samples and that there is no competition from solvent for adsorption sites. The experimental data points have been fitted to the modified B.E.T. equation in order to know the adsorptive capacities (Xm) of the solids as well as their surface areas (S) available to the malathion molecules. Xm values range from 1.35x10−1 molxKg−1 up to 2.47x10−1 molxKg−1, the maximum values corresponding to the sample activated with 0.5 N HNO3 solution and treated at 110°C. S values range from 70x103 m2xKg−1 up to 128x103 m2xKg−1, the maximum values also corresponding to the sample activated with 0.5 N HNO3 solution and treated at 110°C.