Removal of Lead Ions from Aqueous Solution Using Multi-Walled Carbon Nanotubes: The Effect of Functionalization

This study evaluates the lead adsorption efficiency of pristine multi walled carbon nanotubes (raw-MWCNTs), oxidized multi-walled carbon nanotubes (o-MWCNTs) and functionalized multi-walled carbon nanotubes with Tris (2-aminoethyl) amine ( MWCNTs- TAA) from aqueous solution. Functionalization reactions were accomplished using acid treatment. MWCNTs- TAA and o-MWCNTs were characterized using scanning electron microscopy (SEM), Fourier transform infrared (FTIR), Raman spectroscopies, and thermal gravimetric analyzer (TGA). The results indicated that the oxidation and functionalization reactions successfully occurred. The adsorption of Pb(II), onto nano particles were investigated using batch equilibrium adsorption experiments and determined by the flame atomic absorption spectrometry (FAAS). The effects of pH, contact time, initial Pb(II) ions concentration, and adsorbent dosage on the adsorption process were studied. The obtained results revealed that removal of Pb(II) ions from water strongly depends on the pH of the sample solution. Maximum adsorption capacities of Pb(II) ions under the optimal conditions were 6.7, 27.8, 71 mg/g for raw- MWCNTs, o- MWCNTs and MWCNTs-TAA respectively. This means that oxidation and functionalization reactions leads to higher adsorption capacity in comparison to raw- MWCNTs. Regarding to desorption experimental, regenerated MWCNTs can be reused over four times without considerable loss of adsorption capacity. The obtained data were fitted with the Langmuir and Freundlich isotherm adsorption models. It was found that the Langmuir equation can satisfactorily explain the experimental data obtained for Pb(II) for all of the used sorbents.