Removal of heavy metals from aqueous solution by carbon nanotubes:adsorption equilibrium and kinetics

Carbon nanotubes prepared by catalytic chemical vapor deposition of hydrocarbon at 650 degrees C show good adsorption capability of Pb2+, Cu2+ and Cd2+ ions from aqueous solution after oxidized with concentrated nitric acid at 140 degrees C for 1 h. The specific surface area and particle size distribution of the as-grown and oxidized CNTs were studied by BET method and laser particle analyzer. Three kinetic models, that is, first-, pseudo second- and second-order, were used to investigate the adsorption data and the pseudo second-order model can represent the experimental data better than two others. The equilibriumdata fitted well with the Langmuir model and showed the following adsorption order: Pb2+ > Cu2+ > Cd2+.