Abstract
Removal of Pb(II) from aqueous solutions by sorption onto activated carbon is investigated in this paper. Batch experiments are conducted to study the effects of the main parameters such as contact time, initial concentration of Pb(II), adsorbent dose, solution pH, agitation speed, ionic strength and temperature on the sorption of Pb(II) by activated carbon. The maximum removal of lead(II) is found to be 94 % at pH 5.8, initial Pb(II) concentration of 10 mg dm−3, adsorbent dose of 1 g L−1, agitation speed of 200 rpm, ionic strength of 0.005 M, and temperature of 25 °C. Dynamics of the sorption process are studied and the values of rate constants of pseudo-first-order, pseudo-second-order, intraparticle diffusion and intraparticle diffusion coefficient are calculated. The kinetics of lead(II) sorption in activated carbon follows the intraparticle diffusion model, and the data related by two straight lines indicate that the intraparticle diffusion is not the only rate controlling step. Equilibrium isotherms for the sorption of Pb(II) are analyzed by Langmuir, Freundlich and Temkin isotherm models. Freundlich isotherm is found to represent better the data of Pb(II) sorption onto activated carbon. Different thermodynamic parameters Such as changes in standard free energy, enthalpy and entropy are also evaluated and the results suggest that the sorption reaction is spontaneous and endothermic in nature.
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