Adsorption Of Eu (â…¢) And Cu (â…¡) On Multi-walled Carbon Nanotubes

Contacting with oxidants may introduce a variety of oxygen-containing functional groups on multi-walled carbon nanotubes (MWCNTs), which affects the acid-base chemistry of MWCNTs and the interactions with heavy metal ions-the bases of the efficient use of MWCNTs and the understanding of the behaviors of MWCNTs in the environment.MWCNTs at different oxidation levels (MWCNTs-x, x represents the concentration of nitric acid) were prepared by oxidizing the pristine sample (MWCNTs-0) with nitric acids of variable concentrations (22%,44%,66% respectively) and characterized by TEM and X-ray photoelectron spectroscopy (XPS). The specific surface areas of the samples were measured. The acid-base chemistry of the MWCNTs-x was studied by using continuous potentiometric titrations at three ionic strengths (0.01,0.1 and 0.4 mol/L NaCl). It was found that the amount of oxygen-containing functional groups of MWCNTs-x increased with the oxidation level, but the oxidation did not obviously affect the specific surface areas of MWCNTs-x.The adsorption of Eu(â…¢) and Cu(â…¡) on MWCNTs-x was studied as a function of pH, ionic strength, adsorbate concentration, solid to liquid ratio and the presence of fulvic acid (FA) and salicylic acid (SA) using a batch technique, respectively. It was found that the oxidation level of MWCNTs-x had a significant influence on Eu(â…¢) adsorption. The adsorption of Eu(â…¢) on MWCNTs-x increased with increasing pH and decreased with the increase of ionic strength. Moreover, the Eu(â…¢) adsorption isotherms on MWCNTs-x could be fitted by Freundlich equation. It was found that the adsorption of Cu(â…¡) on MWCNTs-66 was strongly affected by pH but insensitive to ionic strength. The presence of FA enhanced obviously Cu(â…¡) adsorption, whereas the presence of SA had no effective effect on the adsorption of Cu(â…¡). The adsorption isotherms of Cu(â…¡) on MWCNTs-66 could be fitted by Langmuir and Freundlich equations.The results of the present thesis confirmed that the amount of oxygen-containing functional groups of MWCNTs can be significantly increased by oxidation and consequently the adsorption capacities of MWCNTs for heavy metals will be obviously increased, which indicated that MWCNTs after oxidation have a good prospect in the heavy metal containing sewage treatment as well as the nuclear waste management.