ADSORPTION OF METHYLENE BLUE FROM AQUEOUS SOLUTION ONTO CARBON NANOTUBES AND ITS THERMODYNAMICS

Methylene blue(MB) was chosen as a model dye to investigate the adsorption behaviors of basic dye from aqueous solution onto carbon nanotubes(MWCNTs). Adsorption isotherm of MB onto the MWCNTs was determined at 290,300 and 310K respectively, by using 10mg/L as the initial concentration of MB. Adsorption equilibrium was attained within 8h. Adsorption equilibrium data were fitted to the Langmuir, Freundlich and Sips models and isotherm constants were determined.The equilibrium data were best represented by the Sips isotherm model. The adsorption amount increased gradually with the increase of pH from 3 to 7. Thermodynamic parameters like changes in the free energy of adsorption(G), enthalpy(H) and entropy(S) were calculated. The negative values of G indicates that the MB adsorption process is a spontaneous in nature and dominated by physical adsorption. The positive value of H andS show the endothermic nature of MWCNTs system and the increasing confusion degree of MWCNTs system,respectively.