Removal of chromium(VI) from wastewater by activated carbon developed from Tamarind wood activated with zinc chloride

In this work, the adsorption of chromium(VI) was studied on activated carbon prepared from Tamarind wood with zinc chloride activation. Adsorption studies were conducted in the range of 10–50 mg/l initial chromium(VI) concentration and at temperature in the range of 10–50 °C. The experimental data were analyzed by the Freundlich isotherm and the Langmuir isotherm. Equilibrium data fitted well with the Langmuir model and Freundlich model with maximum adsorption capacity of 28.019 mg/g. The rates of adsorption were found to confirm to pseudo-second-order kinetics with good correlation and the overall rate of chromium(VI) uptake was found to be controlled by pore diffusion, film diffusion and particle diffusion, throughout the entire adsorption period. Boyd plot confirmed that external mass transfer was the rate-limiting step in the adsorption process. Different thermodynamic parameters, viz., ΔH°, ΔS° and ΔG° have also been evaluated and it has been found that the adsorption was feasible, spontaneous and endothermic in nature. The results indicate that the Tamarind wood activated could be used to effectively adsorb chromium(VI) from aqueous solutions.