Thermodynamic and Kinetic Studies of Chromium (VI) Adsorption by Sawdust Activated Carbon

Low cost activated carbon, prepared from saw dust of Ziziphus jujube by chemical activation with phosphoric acid (H3PO4) was characterized and utilized for the removal of Cr (VI) ions from aqueous solutions under different conditions of solution pH, contact time, initial concentration, carbon dose and temperature. Adsorption of Cr (VI) ions was found highly pH dependent that increased with decrease in solution pH. The removal of Cr (VI) ions increased with increase in temperature, initial concentration and contact time until equilibrium was established. Langmuir's adsorption isotherm model and pseudo - second order kinetic equation were found better fitted to describe the experimental data. Thermodynamic study revealed the feasibility, spontaneity and endothermic nature of the adsorption process. The used carbon was regenerated by treating with HCl solution. In comparison to other adsorbents, the results indicated that the prepared saw dust activated carbon could be an eco-environment friendly and efficient adsorbent for removal of Cr (VI) ions from aqueous solutions.