Kinetics and Thermodynamics Studies on the Adsorption of Hexavalent Chromium (Vi) onto Activated Carbon Prepared from Wood Apple Tree (Limonia acidissima) Barks

An efficient adsorbent was developed from barks of Wood apple (Limonia Acidissima) and its diverse adsorption properties were examined for the removal of Cr(VI) from aqueous solutions. Prepared carbon was designated as WAAC - Wood Apple tree bark Activated Carbon and it was used as an adsorbent. The effects of contact time, adsorbent dosage, pH, initial Cr(VI) concentration, and temperature on adsorption were evaluated through batch mode experiments. For all the initial concentrations studied, equilibrium was reached in 80 minutes. The adsorption kinetics adhered to a pseudo-second-order rate kinetic model, with intra-particle diffusion serving as the rate-determining step. Various thermodynamic parameters, such as Gibbs free energy (G), enthalpy (H) and entropy (S), of the adsorption process have also been assessed. The analysis of these values suggested that the adsorption process was endothermic, spontaneous, and occurred with increased randomness.