Nanotechnology holds great potential in the sector of water/wastewater treatment since it is considered as an advanced technology for improving water quality. Carbon nanotubes is a carbonaceous material that shows exceptional adsorption capacity for the removal of heavy metals due to their novel properties. Thus their application for the treatment of industrial wastewater or contaminated groundwater exhibits high interest. In this study the efficiency of multiwall carbon nanotubes as adsorbent for hexavalent chromium, manganese, lead and cadmium removal as a function of pH and the initial concentration of heavy metal is investigated. In addition, the occurrence of any competitive effects amongst the aforementioned metals during adsorption is investigated. For this reason batch experiments are performed keeping constant the concentration of multiwall carbon nanotubes (2 g/L) and the contact time (5 h).