Adsorption of Methyl Orange on Bentonite: Design, Modeling, and Analysis of Experiments

The study examines the possibility of removing Methyl Orange (MO) from aqueous solutions using crude bentonite. SEM-EDX (scanning electron microscopy) and XRD (X-Ray Diffraction) analyses were performed to characterize the material. Batch experiments were performed on the adsorption process to study the effect of contact time, pH, concentration, and temperature. The results indicate that the equilibrium reaches after 2 h of contact. The MO adsorption followed the Langmuir-Freundlich and Baudu models with a maximum adsorption capacity of 308 mg/g. The adsorbed capacity of the material is best at pH=3. The adsorption capacity increases with temperature.  In addition, the Central Composite Design (CCD) in Response Surface Methodology (RSM) and Artificial Neural Network (ANN) were used to evaluate the simultaneous interactions of independent variables. The results suggest that the initial concentration was the dominant parameter in the adsorption process. The monolayer model with two energies derived from statistical physics can be adapted to interpret the adsorption data. Physical adsorption forces were predicted to be responsible for the removal of the dye. This study provides new information on the adsorption mechanisms of pollutants commonly found in water.