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

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 degreesC in SO2 (C-SO2-N-2-30), at 30 degreesC in two successive steps: first in SO2 and then in H2S (C-SO2-H2S-N-2-30), and from room temperature to 900 degreesC in SO2 (C-SO2-900). The samples were characterized by N-2 adsorption at -196 degreesC 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 degreesC. The amount of sulfur introduced in C S is much larger for C-SO2-H2S-N-2-30 and C-SO2-900 than for C-SO2-N-2-30. For C-SO2-H2S-N-2-30 and C-SO2-900, also, the loss of surface area and porosity is greater than for C-SO2-N-2-30. 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-N-2-30 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. (C) 2004 Elsevier Ltd. All rights reserved.