Isotherm, thermodynamic, kinetics, and adsorption mechanism studies of Ethidium bromide by single-walled carbon nanotube and carboxylate group functionalized single-walled carbon nanotube

The studies of kinetics and thermodynamics of adsorption of Ethidium bromide in aqueous solutions on single-walled carbon nanotube (SWCNT) and carboxylate group functionalized single-walled carbon nanotube (SWCNT-COOH) surfaces were by UV-Vis spectroscopy. The adsorption kinetics for SWCNT-COOH and SWCNTs were well described by a intra-particle diffusion model, while Langmuir, Freundlich, Harkins-Jura, and Halsey 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 maximum surface coverage for SWCNTs is 36.10% and for SWCNT-COOH is 38.42%. The values of Delta H-0 and Delta G(0) suggested that the adsorption of EtBr on SWCNT-COOH and SWCNTs was endothermic and spontaneous. The adsorption of EtBr on SWCNT-COOH is more than SWCNTs surfaces. (C) 2012 Elsevier Inc. All rights reserved.