Chemical vapor deposition was used for synthesis of CNT sheets. The CNT sheets were then oxidized with concentrated nitric acid at room temperature. The results demonstrate that the adsorption capacity of the CNT sheets increases significantly after oxidation process. Also, increasing initial salts concentration increases the adsorption capacity of the CNT sheets. The adsorption behaviors of heavy metal ions onto the oxidized CNT sheets match well with Langmuir and Freundlich isotherms. The results demonstrated that kinetics of adsorption varies with initial concentration of heavy metal ions. The preference order of adsorption on the oxidized CNT sheets is Pb2+ > Cd2+ > Co2+ > Zn2+ > Cu2+. Using the oxidized CNT sheets as adsorbent, economical waste water treatment without CNT leakage into water is feasible. The oxidized CNT sheets are promising materials for pre-concentration and solidification of heavy metal ions from large volume of solutions