Effect of functional groups in the structure of carbon nanotubes to adsorption grade of cadmium ions

In the present work, it was studied the effect over the adsorption capacity of Cd(II) ions in carbon nanotubes (NTC) by adding several functional organic groups on its structure as: –OH, –C=O, –CH and –COOH, using as precursors: sulfuric acid, nitric acid, hydrogen peroxide, methanol, acetic acid and acetone. The modificated nanotubes (NTC'f) were characterized by transmission electron microscopy (TEM), scanning electron microscopy (SEM), X-ray diffraction (XRD) and Fourier transform infrared (FTIR) to reveal the modified morphology and structure. In order to evaluate the adsorption performance of NTC'f for Cd(II) ions, a UV-Vis spectrophotometer was used. Several parameters were evaluated: Cd(II) ions concentration, solution pH and samples exposure time to NTC'f. Finally, a relationship between structure and functionality of the NTC'f and the Cd(II) ions adsoption was found, where the funtionalized nanotubes with -COOH and -OH exhibited a higher adsorption rate at room temperature, pH= 6, exposure time of 72 hours, where the NTC’f were able to absorb a 100 % of Cd(II) ions in a 50 mg.g-1 ratio.

Keywords: adsorption, functionalization, carbon nanotubes, cadmium ions, metal.