Optimized Preparation of High Value-Added Activated Carbon and Its Adsorption Properties for Methylene Blue

The optimal preparation conditions of activated carbon (AC) derived from corncob (CC) by steam activation were investigated using response surface methodology. In response to iodine adsorption capacity, experimental design was established using three synthetic variables based on the Box-Behnken central composite design. The optimum conditions of 892 degrees C activation temperature, 40 min residence time, and 1:1.6 the mass ratio of char to H2O gave 1216.74 mg/g iodine adsorption value. AC was characterized using instrumental analyses consist of Brunauere-Emmette-Teller (BET), Fourier transform infrared (FT-IR) and Scanning electron microscopy (SEM). The effect of experimental parameters such as adsorption time, adsorbent dosage and pH on the uptake of methylene blue (MB) were studied. Experimental equilibrium data was analyzed by the Langmuir, Freundlich, Sips and Koble-Corrigan isotherm models. The results showed that the Freundlich and Koble-Corrigan models could properly represent the adsorption behavior of MB on AC. In addition, it was known that the adsorption of MB was a spontaneous and endothermic process from the thermodynamic parameters of Delta G, Delta H and Delta S.