Equilibrium and Kinetic Study of Adsorption of Mo (VI) and Pd (II) from Aqueous Solutions by Functionalized Multi-Walled Carbon Nanotubes

In this work, a new type of solid adsorbent was prepared by functionalization of carbon nanotubes and the structure and morphologies of the amine-functionalized Multi-walled carbon nanotubes were characterized by Fourier transform infrared spectroscopy (FTIR), thermogravimetric analysis (TGA) and scanning electron microscope (SEM). Its adsorption behavior towards Pd(II) and Mo(VI) ions was investigated. For this purpose, a solid phase extraction process using the prepared adsorbent was carried out in the pH range of 1 to 9. The effect of various parameters such as initial concentration, time and interfering ions on the adsorption amount was investigated, and the optimal conditions for the maximum extraction of the two ions were obtained. The adsorption of these ions by the synthesized MWNTs in real samples was examined and good results were achieved. The negative value of the change in standard Gibbs free energy (ΔG°<0) for Mo(VI) sorption by the adsorbent specify a spontaneous and realizable sorption process. The changes in free energy (ΔG °), enthalpy (ΔH °) and entropy (ΔS °) for Pd(II) ions associated with Mo(VI) ions are reversed. finally, The compatibility of the experimental data with the adsorption isotherms of Langmuir, Freundlich and Redlich-Peterson were investigated for the adsorption of Mo(VI) and Pd (II) the modified carbon nanotubes.