Synthesis of activated carbon material using sawdust as precursor and its application for dye removal: batch study and optimization using response surface methodology

In the present study, an inexpensive adsorbent has been synthesized from waste sawdust which can remove the highly toxic dye indigo carmine (IC) from aqueous solution. Activated carbon from sawdust was synthesized using physical and chemical treatment. After using the adsorbent in batch-dye adsorption experiments, it has been characterized by SEM, FT-IR and XRD which showed significant up-taking capacity (77%) of the dye on its surface. Sensitivity of the dye removal process has been analysed by undergoing batch study with varying initial concentrations of the IC dye, adsorbent dose, pH and temperature and optimization of the process which indicated the optimum condition of the experimental parameters. Various isotherm models and kinetic models have been used for fitting of experimental data and examined to analyse efficiency of the adsorption mechanism. Langmuir isotherm and pseudo-second-order kinetics were found to be followed by adsorption process over the entire dataset of tested experimental results. The maximum uptake capacity was found to be 30 mg g⁻¹. Thermodynamic investigation was also conducted to project the spontaneity of the reaction.