Adsorption of chloridazon from aqueous solution on heat and acid treated sepiolites

The adsorption of chloridazon on heat treated sepiolite samples at 110 degrees C (S-110), 200 degrees C (S-200), 400 degrees C (S-400), 600 degrees C (S-600) and acid treated samples with H2SO4 solutions of two different concentrations (0.25 and 1.0 M) (S-0.25 and S-1.0, respectively) from pure water at 25 degrees C has been studied by using batch experiments. In addition, column experiments were carried out with the natural (S-10) and 600 degrees C(S-600) heat treated samples, using a 10. 30 mg l(-1) aqueous solution of chloridazon. The adsorption experimental data points have been fitted to the Freundlich equation in order to calculate the adsorption capacities (K-f) of the samples; Kf values range from 2.89 mg kg(-1) for the S-1.0 sample up to 164 mg kg(-1) for the S-600 sample; so, the heat treatment given to the sepiolite greatly increases its adsorption capacity for the herbicide chloridazon whereas the acid treatment produces a clear decrease in the amount of chloridazon adsorbed. The removal efficiency (R) has also been calculated; R values ranging from 5.08% for S-1.0 up to 60.9% for S-600. The batch experiments showed that the strongest heat treatment is more effective than the natural and acid treated sepiolite in relation to adsorption of chloridazon. The column experiments also showed that 600 degrees C heat treated sepiolite might be reasonably used in removing chloridazon from water. Thus, as this type of clay is relatively plentiful, these activated samples might be reasonably used in order to remove chloridazon from water. (c) 2005 Elsevier Ltd. All rights reserved.