OPTIMIZATION OF PROCESS CONDITIONS FOR ADSORPTION OF METHYLENE BLUE ON FORMALDEHYDE-MODIFIED PEANUT SHELLS USING BOX-BEHNKEN EXPERIMENTAL DESIGN AND RESPONSE SURFACE METHODOLOGY

This paper presents the use of formaldehyde-modified peanut shells as bioadsorbent for the adsorption of methylene blue for the first time. Firstly, the effect of medium pH, which is one of the important parameters for adsorption process, was determined. Then, the adsorption process conditions such as adsorption time (30-150 min), initial concentration (50-200 ppm) and ambient temperature (25-40°C) were optimized by using response surface methodology (RSM) based on Box-Behnken experimental design. The pseudo-first order and pseudo-second order kinetic models were used to evaluate the adsorption kinetic in this study under optimized process conditions . The maximum adsorption capacity was found under optimum process conditions; 92.25 min adsorption time, 191.87 ppm initial concentration, 39.70°C adsorption temperature. The maximum adsorption capacity for methylene blue was determined to be 43.84 mg/g using RSM based on Box-Behnken experimental design. Adsorption kinetic results showed that the plots of the pseudo-second order kinetic model were fit the experimental data better when compared to the pseudo-first order model. In addition, results indicated that formadehite-modified peanut shells could be used as low cost and effective bioadsorbent for the adsorption of methylene blue, which is one of the important dyes. Furthermore , it was concluded that the RSM based on Box-Behnken experimental design can be applied successfully for the methylene adsorption process.