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℃ show good adsorption capability of Pb 2+ , Cu 2+ and Cd 2+ ions from aqueous solution after oxidized with concentrated nitric acid at 140℃ 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 equilibrium data fitted well with the Langmuir model and showed the following adsorption order: Pb 2+ >Cu 2+ >Cd 2+ .