Hemicellulose-Based Absorbent Toward Dye: Adsorption Equilibrium and Kinetics Studies

Exploitation of biomaterials derived from renewable resources as absorbents for the removal of dyes from industrial effluents is of great importance. In this work, the efficiency of the hemicellulose-based absorbent for the adsorption of methylene blue dyes was systematically examined. It was found that the hemicellulose-based absorbent removed the dyes from aqueous solution very effectively. The study on the kinetics of methylene blue onto hemicellulose-based absorbent showed that experimental data followed a pseudo-second-order model, suggesting that the adsorption process was controlled by chemical-sorption. The equilibrium data was also fitted to the two isotherm models, Langmuir and Freundlich ones; and it was found that Langmuir model presented the best fit, showing the maximum adsorption capacity of 39.22 mg/g at 25 °C. The thermodynamic parameters, including the standard enthalpy, entropy and free energy obtained from this work, indicated that the adsorption of methylene blue onto hemicellulose based absorbent is an endothermic and spontaneous process. Overall, the adsorption process of methylene blue to hemicellulose-based absorbent is a combination of chemical-sorption and physical-sorption.