Adsorption of Pb(II), Cd(II) and Cu(II) Ions in Aqueous Solution on SWCNTs and SWCNT -COOH Surfaces: Kinetics Studies

The studies of kinetics and thermodynamics of adsorption of Pb(II), Cd(II) and Cu(II) ions in aqueous solutions on single-walled carbon nanotube (SWCNTs) and carboxylate group functionalized single-walled carbon nanotube (SWCNT-COOH) surfaces were by atomic absorption spectroscopy. The adsorption kinetics was well described by a pseudo-second-order rate model, while Langmuir, Freundlich, Redlich-Peterson (R-P) and Tempkin isotherms described the adsorption isotherms, and the adsorption thermodynamic parameters of equilibrium constant (K-0), standard free energy (Delta G(0)), standard enthalpy (Delta H-0) and standard entropy changes (Delta S-0) were measured. The adsorption of Pb(II), Cd(II) and Cu(II) ions from aqueous solutions on SWCNTs and SWCNT-COOH. The values of Delta H-0 and Delta G(0) suggested that the adsorption of mentioned ions on SWCNT-COOH and SWCNT were endothermic and spontaneous. The adsorption of mentioned ions on SWCNT-COOH is more than SWCNTs surfaces.