The Studies of Equilibrium and Thermodynamic Adsorption of Pb(II), Cd(II) and Cu(II) Ions from Aqueous Solution onto SWCNTs and SWCNT–COOH Surfaces

The equilibrium and thermodynamics of Pb(II), Cd(II) and Cu(II) ions adsorption from aqueous solution onto single-walled carbon nanotube (SWCNT) and carboxylate group functionalized single-walled carbon nanotube (SWCNT-COOH) surfaces were studied by atomic absorption spectroscopy. The effect of contact time, pH, initial concentration of ion, ionic strength and temperature on the adsorption of ion was investigated. The results indicated that Langmuir model fits adsorption isotherm data better than the Freundlich model. The results also demonstrated that SWCNT-COOH surfaces can more effectively adsorb mentioned ions than a SWCNT surface. Maximum adsorption capacities (qm) for Pb(II), Cu(II) and Cd(II) ions onto SWCNT-COOH were obtained as 96.02, 77.00 and 55.89 mg/g, respectively, and by SWCNTs as 33.55, 24.29 and 24.07 mg/g, respectively. Thermodynamic parameters values showed that the adsorption of ions on SWCNT-COOH and SWCNTs at 283–313 K is spontaneous and endothermic.