Batch sorption of Pb(II) ions from aqueous solutions using activated carbon prepared from date stones: equilibrium, kinetic, and thermodynamic studies

Abstract

The sorption of Pb(II) ions onto activated carbon prepared from Tunisian date stones was studied in a batch process. The effects of the main parameters, such as contact time, initial concentration of Pb(II), solution pH, and temperature were studied. The kinetic data were analyzed by applying pseudo-first-order, pseudo-second-order, and Weber-Morris diffusion models. The applicability of Langmuir and Freundlich adsorption isotherms was evaluated to better understand the adsorption process. The results revealed that the equilibrium data were perfectly represented using a Langmuir isotherm. The maximum monolayer adsorption capacity was found to be 38.46 mg/g at 20°C, pH 6, contact time 120 min, and 0.5g activated carbon. The kinetic data followed closely the pseudo-second-order model. The application of an intraparticle diffusion model revealed that the adsorption mechanism of Pb(II) is a rather complex process and that diffusion is involved in the overall rate of the adsorption process, but it is not the only rate-controlling step. Thermodynamic studies revealed the spontaneous and endothermic nature of the adsorption process. Results from this study suggest that activated carbon produced from date stones residue is an effective adsorbent for the removal of lead from aqueous solutions.