Adsorptive removal of chromium (VI) from aqueous solution over powdered activated carbon: Optimisation through response surface methodology

This paper investigates the adsorptive removal of Cr (VI) from aqueous solution over commercial powdered activated carbon (PAC) and carries optimisation of removal efficiency for the process using response surface methodology (RSM). The effects of different parameters such as pH, initial Cr (VI) concentration, adsorbent dose, contact time and temperature on adsorption were studied to find the best operating conditions. This study showed that when initial concentration was 50 ppm, 100% Cr (VI) removal was possible with pH 2 and 2 g L-1 PAC concentration. Different adsorption kinetic models and isotherms were compared respectively with the proposed kinetic model based on liquid phase adsorbate concentration and the developed new three-parameter isotherm. The new isotherm supported the experimental results with a better accuracy. The main process parameters considered for optimisation were pH, adsorbent dose and adsorption time. The experimental was designed according to central composite rotatable design (CCRD) and second order regression model was developed for regression analysis and ANOVA study. The optimum pH, PAC dose and time were found to be 2.32, 1.79 g L-1 and 25.76 min. Pareto analysis established that PAC dose was the most influential parameter. (C) 2011 Elsevier B.V. All rights reserved.