Carbon nanostructures are novel materials that are been investigated for diverse applications, but just a few studies have been focused on environmental problems. In this work, the competitive adsorption of phenol, cadmium and lead onto N-doped carbon nanotubes (CNx) modified by air (MCNx) was investigated. The CNx and MCNx were characterized by SEM, EDX, TGA, elemental analysis and their surface areas were determined. The adsorption experiments of toxic pollutants were carried out in batch reactors at 25°C. The characterization of MCNx by these techniques showed an increase in oxygen content and surface area in comparison with CNx nanotubes. The adsorption capacity was 0.14, 0.09 and 0.07 mmol/g for phenol, Cd~(2+)and Pb~(2+), respectively. The experimental data of the competitive adsorption at equimolar concentration of the organic compound and heavy metal revealed a decreased in Pb~(2+) removal in presence of phenol at equilibrium concentrations > 0.4 mmol/L. On the other hand, when Cd~(2+) and phenol where combined, the cadmium removal was favored as the phenol concentration increased, whereas the phenol adsorption capacity was not affected at any cadmium concentration. These results suggest that MCNx have a great potential to be used in environmental applications as adsorbents of organic and inorganic compounds present in aqueous phases.
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