Decolourization of aqueous Methylene Blue solutions by corn stalk: modeling and optimization

The aim of the current study was to synthesis activated carbon from corn stalk using a simple thermal activation method. The physical and chemical characteristics of prepared activated carbon have been investigated using scanning electron microscopy, Brunauer-Emmett-Teller, Fourier-transform infrared spectroscopy, and pH of zero point charge (pH(ZPC)). Then, the application of the prepared corn stalk activated carbon was investigated to remove the Methylene Blue (MB) dye from aqueous solution. The effect of four independent factors including initial concentration (10-210 mg L-1), adsorbent dosage (0.2-1.4 g L-1), pH (3-11), and contact time (10-50) were also evaluated by response surface methodology at five levels. Complete dye removal was observed at an initial concentration of 10 mg L-1, and adsorbent dosage of 1.4 g, pH of 11, and contact time of 50 min. The adsorption kinetics was also described by the pseudo-second-order model with R-2 = 0. 9833. The results of comparison equilibrium data between Langmuir and Freundlich models showed that the adsorption process was best described by Freundlich with the maximum adsorption capacity q(m) = 2.34 mg g(-1). The experimental data were also fitted with Freundlich isotherm (R-2 = 0.91). Base on the results, it can be concluded that corn stalk activated carbon produced from agricultural wastes is a highly promising nontoxic and environmentally friendly adsorbent with great potential for removing of MB.