The Investigation Adsorption of Malachite Green by MWCNTs and f-MWCNT Surfaces: Thermodynamics and Equilibrium

Abstract

The effect of temperature on the equilibrium adsorption of malachite green dye from aqueous solution using multi walled carbon nanotubes (MWCNTs) and functionalized multi walled carbon nano tubes with carboxyl group (f-MWCNTs) were investigated. The equilibrium adsorption data were analyzed using adsorption isotherm models. Three isotherm models were used to describe the isotherm data (Langmuir, Temkin, and Henderson). The adsorption of malachite green by f-MWCNTs and f-MWCNTs was studied at different temperatures. Standard free energy changes (δG˚), standard enthalpy change (δH˚), and standard entropy change (δS) are calculated using adsorption equilibrium constants. All (δG˚) values were negative, while the δH˚ values of MWCNTs and f-MWCNTs surfaces were 4.78 and 2.53 kJ/mol, respectively. Moreover, δS˚ values of malachite green in adsorption by MWCNTs and f-MWCNTs surfaces were 0.03 and 0.02 kJ/mol, respectively. The results show that that the malachite green adsorption by MWCNTs and f-MWCNTs was a spontaneous and endothermic process and is suitable for adsorbent surface.