Abstract
This study explains the use of modified activated carbon (microporous or mesoporous) as adsorbents for the removal of lead ions from water. The modifications involved the following: (i) oxidation, to introduce oxygen-containing functional groups, and (ii) treatment with aqueous ammonia, to introduce basic nitrogen functional groups. The pristine materials, namely, those after surface modifications and those after adsorption, were characterized by the adsorption of nitrogen, Fourier transform infrared spectroscopy, scanning electron microscopy and thermal analyses. We conducted batch experiments to study the effect of initial concentration, pH and temperature on the removal of Pb2+. Our experiments showed that adsorption was pH dependent, and any rise in temperature results in increased adsorption, which indicates the endothermic nature of the process. Typical isotherm models were fitted to describe the data. In addition, during adsorption, homogeneous accumulation of lead ions on the carbonaceous surface was observed. The higher adsorption capacity of chemically oxidized mesoporous carbon for lead was mainly due to the presence of functional groups of oxygen and nitrogen on the surfaces of activated carbon, which presumably react with the metal ions to form salt or complexes that deposit on the carbon surface.