Optimization and Kinetic Study for the Removal of Chromium (VI) Ions by Acid Treated Sawdust Chitosan Composite Beads

Abstract

Aims: To study the adsorption efficiency of acid-treated sawdust composite beads (SDCCB) for Cr(VI) ions and to optimize the process variables using Response Surface Methodology (RSM). Study Design: Preparation of SDCCB, Characterization of SDCCB, Study of influence of variables on adsorption efficiency of SDCCB for Cr(VI) ions from aqueous solutions and optimization of process variables using RSM. Place of Study: Department of Chemistry, Khadir Mohideen College, Adirampattinam, Tamilnadu, India. Methodology and Results: The morphology and surface properties of the adsorbent have been characterized by scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR) and BET analyzer. RSM has been used to optimize the process variables such as initial metal ion concentration, adsorbent dosage and pH of the solution on the performance of percentage removal of Cr(VI) ions and adsorption capacity of SDCCB. Various isotherm and kinetic models have been fitted with experimental data to describe the solute interaction and behaviour of rate controlled mechanism with the adsorbent in batch studies. Conclusion: SDCCB is an effective, economic and eco-friendly adsorbent for the removal of nearly 95% of Cr(VI) from aqueous solutions. The mathematical model development and optimization for adsorption of Cr(VI) using statistical design of experiments appears to be a useful tool to predict and understanding the interaction effects between process variables. The isotherm models for the experimental data followed is in the order of Freundlich > Langmuir > Temkin isotherm for adsorption of Cr(VI) ions and adsorption kinetics fit suitably in a pseudo second order kinetic model. The activation parameters evaluated points out that the adsorption of Cr(VI) on SDCCB surface is an endothermic chemisorption process.