where KF (mg/g) and n are the Freundlich constants characteristics of the system, indicating the adsorption capacity and the adsorption intensity, respectively. The values of KF and correlation coefficient (R2) obtained from Freundlich curves were 1.306 L/g and 0.996, respectively ( Fig. 9b). The adsorption of Alizarin Red S better fitted to the Freundlich isotherm model with the higher R2 of 0.996. Based on the comparison of the Langmuir and Freundlich models and the results obtained at 303 K, the Freundlich model has exhibited a better fit to the adsorption data than the Langmuir model.