Adsorption of Pb2+ in aqueous solution by SO2-treated activated carbon Original Research Article

The adsorption of Pb2+ in aqueous solution by SO2-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 SO2 (C–SO2–N2-30), at 30 °C in two successive steps: first in SO2 and then in H2S (C–SO2–H2S–N2-30), and from room temperature to 900 °C in SO2 (C–SO2-900). The samples were characterized by N2 adsorption at −196 °C and by helium and mercury density measurements. The adsorption process of Pb2+ was studied using Pb2+ 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–SO2–H2S–N2-30 and C–SO2-900 than for C–SO2–N2-30. For C–SO2–H2S–N2-30 and C–SO2-900, also, the loss of surface area and porosity is greater than for C–SO2–N2-30. The introduction of sulfur in C–S significantly slows down the adsorption rate of Pb2+ but markedly enhances the extent to which it occurs, except at pH 2.0. The removal of sulfur from C–SO2–H2S–N2-30 and C–SO2-900 noticeably favors the kinetics and also the adsorption of metallic ion. The process may be then as fast as for C–S.