Batch adsorption of indigo carmine on activated carbon prepared from sawdust: A comparative study and optimization of operating conditions using Response Surface Methodology

Abstract

Raw sawdust was used to prepare two chemically activated carbon — one after treating with Ortho-phosphoric acid and another using sodium hydroxide. The adsorbents thus prepared were used to study indigo carmine removal under batch mode. The adsorbents were thus characterized and compared using the results. The isotherm models were employed to test the adsorption isotherm data. The Langmuir model showed the best fit among the models for both of the adsorbents. The pseudo-second-order model characterized the kinetic behaviour for both of the adsorbents. The thermodynamic results implied that the process was exothermic. The activated carbon prepared after activation with Orthophosphoric acid gave better removal than the one activated with Sodium Hydroxide; hence a Fourier Transform Infrared (FT-IR) spectroscopy was performed. Further, a Response Surface Methodology Optimization of the operating conditions was done using it as the adsorbent.