Active carbon as an adsorbent for lead ions

A commercial active carbon has been tested as an adsorbent for the removal of lead ions from aqueous solutions. Optimum conditions for maximum adsorption in terms of shaking time, lead ion concentration, temperature and concentration of different acids were established. The results obtained reveal that the adsorption of lead ions on active carbon is athermic (Delta H = 0) in nature and follows first-order kinetics. The first-order rate constant was evaluated as 0.049 min(-1) and the intraparticle diffusion rate as 3.07 x 10(-4)(g/g min(1/2)). The data also obey the Freundlich, Langmuir and Dubinin-Radushkevich (D-R) isotherm equations over the concentration range studied. The magnitude of the adsorption energy, 7.61 kJ/mol, calculated from the beta-constant of the D-R equation lies in the energy range for physical adsorption which is attributed to weak bonding between the lead ions and the active carbon.