Optimization of key parameters for chromium (VI) removal from aqueous solutions using activated charcoal.

Commercial activated charcoal was investigated for removal of Cr(VI) from aqueous solutions. The effects of altering the initial Cr(VI) concentration, pH, contact time and amount of activated charcoal were studied. Maximum adsorption of Cr(VI) was achieved between pH 1 - 3 and after a contact time of 120 min. The percentage of Cr(VI) removed decreased from 99.99 - 90.83% when the initial Cr(VI) concentration was increased from 0.05 - 0.5 mg ml-1 at pH 2 and 26 ± 2°C. Various kinetic models such as pseudo first-order, pseudo second-order and Elovich models were used to evaluate the mechanism of Cr(VI) adsorption on activated charcoal. The Cr(VI) removal process was found to be governed by second-order kinetics and the rate constant of the adsorption (k2) was 0.1800 g kg-1 min-1 for an initial Cr(VI) concentration of 0.1 mg ml-1. The adsorption of Cr(VI) was evaluated using Langmuir, Freundlich, and Temkin isotherms and their constants were determined. The maximum adsorption capacity obtained using the Langmuir isotherm model was 45.24 g kg-1 at pH 2.   Key words: Key parameters, activated charcoal, adsorption, aqueous solutions, Cr(VI).