Abstract
The present paper focuses on the valorization of raw and treated Calotropis gigantea fibers as a natural and low-cost biosorbent for methylene blue. To assess the effect of the fiber treatment, chemical, morphological, thermal, and structural characterizations were performed. The adsorption characteristics were achieved by varying the pH, the initial dye concentrations, temperature, and contact time. The pseudo-first-order kinetic model fits accurately the experimental data. The adsorption isotherms have been fitted using several models. The monolayer model with one energy is finally adopted because the error on the parameters inherent to the model is relatively small. The adsorption isotherms of the raw and treated fibers reveal that when the temperature increases, the adsorption capacity is reduced. The maximum adsorption capacity is obtained at the temperature 25°C. It is equal to 31 mg/g and 13 mg/g for the raw fiber and the treated fiber, respectively. The steric parameter
is greater than one for the raw fiber, whereas it is smaller than one for the treated fiber. The adsorption energy is about 19 kJ/mol. The Calotropis gigantea fiber seems to be a potential candidate for the removal of methylene blue from polluted water.