Adsorption Studies of Basic Green 4 from Aqueous Solution on Ca2+ Exchanged Clay

Abstract

Abstract The adsorption of basic green 4 from aqueous solution on calcium exchanged clay (Attock-Ca and Swat-Ca) was studied. Clays were first purified and activated with H2SO4 and then exchanged with Ca2+ ions. Clay was characterized by BET surface area, XRD and SEM/EDS. The adsorption kinetic at 298 K and 306 K showed that the first order models were applied to the data. The rate constant increased with the rise in temperature of adsorption/activation. Thermodynamic properties (ΔE≠, ΔH≠, ΔS≠ and ΔG≠) for the adsorption process were calculated. Positive values of ΔH≠ showed that the adsorption of basic green 4 is endothermic. Positive values of ΔS≠ reflected the increase in the disorder of the system at the solid-solution interface during adsorption. The Gibbs free energy, which is the driving force for adsorption is negative indicating spontaneous adsorption. Freundlich's and Langmuir's models described the equilibrium adsorption study and found to fit the experimental data.