Thermodynamic Investigation of Pb2+ and Cd2+ Ions Absorption from Aqueous Solutions Using Multi-Walled Carbon Nanotubes

In this study, removal of heavy metal ions including cadmium and lead from wastewater were studied. Adsorption process was carried out using simple multiwalled carbon nanotubes (MWCNT) and functionalized MWCNT with the carboxyl agent (MWCNT-COOH) prepared by CVD (chemical vapor deposition) method with a purity of 95%. Furthermore, the effect of temperature at 27.32, 37 and 47°C on absorption rate was investigated, in terms of the other constant variables such as initial content of metal ions, solution pH, contact time and concentration of carbon nano absorbers. Final content of the metal ions remaining in the solution was measured by atomic absorption spectroscopy (AAS). It was revealed that there is a direct relationship between solution’s temperature and cadmium and lead ions absorption rate on carbon nanotubes. Furthermore, thermodynamic calculations of absorption showed that Gibbs free energy (ΔG) of absorption process by MWCNT-COOH and MWCNT is negative. This result indicating the spontaneous absorption reaction and removal of metal cathion by carbon nanotubes. This reaction is endothermic and Positive ΔH confirms it.