Adsorption of as-produced and purified multiwalled carbon nanotubes (MWNTs) to heavy metal using Cu(II) as a model was investigated and characterized by many techniques. The results show that the oxygenous functional groups can be formed on MWNTs after MWNTs were purified. The oxygenous functional groups play an important role in Cu(II) adsorption to form chemical complex adsorption. The adsorption capacity of Cu (II) on as-produced and purified MWNTs increased with the pH in the pH range of 2-7. The Cu (II) species adsorbed on purified MWNTs mainly aggregate on the ends and at the defects sites on the purified MWNTs. The experimental data for metal ions adsorption onto MWNTs were analyzed using the Langmuir and Freundlich models to describe the equilibrium adsorption. The linear correlation coefficients of Langmuir isotherms were obtained and the results revealed that the Langmuir isotherm fitted the experimental results.