Adsorption of Pb 2+ in aqueous solution by SO 2-treated activated carbon

Abstract

The adsorption of Pb 2+ in aqueous solution by SO 2-treated activated carbon was investigated from both kinetic and equilibrium standpoints. A commercial activated carbon (C–S) was used. It was treated at 30 °C in SO 2 (C–SO 2–N 2-30), at 30 °C in two successive steps: first in SO 2 and then in H 2S (C–SO 2–H 2S–N 2-30), and from room temperature to 900 °C in SO 2 (C–SO 2-900). The samples were characterized by N 2 adsorption at −196 °C and by helium and mercury density measurements. The adsorption process of Pb 2+ was studied using Pb 2+ solutions at pH 5.4 and 2.0 and at 25 and 45 °C. The amount of sulfur introduced in C–S is much larger for C–SO 2–H 2S–N 2-30 and C–SO 2-900 than for C–SO 2–N 2-30. For C–SO 2–H 2S–N 2-30 and C–SO 2-900, also, the loss of surface area and porosity is greater than for C–SO 2–N 2-30. The introduction of sulfur in C–S significantly slows down the adsorption rate of Pb 2+ but markedly enhances the extent to which it occurs, except at pH 2.0. The removal of sulfur from C–SO 2–H 2S–N 2-30 and C–SO 2-900 noticeably favors the kinetics and also the adsorption of metallic ion. The process may be then as fast as for C–S.