Application of walnut tree sawdust modified with KMnO4 for removal of methylene blue from aqueous solution in batch system: Isotherm, kinetic and thermodynamic studies

Abstract

In this study, the adsorption of methylene blue from aqueous solution by modifying sawdust with KMnO₄has been studied as an effective adsorbent. The surface and characteristics of the composite are studied by Scanning electron microscopy (SEM), X-ray diffraction (XRD) and Fourier transform infrared spectroscopy (FTIR). The result demonstrate, that by increasing <em>p</em>H, the amount of methylene blue adsorption also increases, and the amount of optimum removal of this dye (96.36%) was obtained at methylene blue dye <em>p</em>H aqueous solution equal to 6 with initial concentration 100 mg L^-1. The studies have shown that the kinetics of the adsorption process follows the pseudo-second-order model with a correlation coefficient R²>0.999, and equilibrium data conform the Langmuir isotherm model with R²>0.9982 and a maximum capacity of single layer adsorption q_eequal to 100 mgg^-1. Thermodynamically, the reaction is endothermic and spontaneous. Consequently, the result has shown, that the modified sawdust can be used as a quick, inexpensive and effective adsorbent in order for removal of methylene blue dye from aqueous solution.