Adsorption of Benzaldehyde on Granular Activated Carbon: Kinetics, Equilibrium, and Thermodynamic

R. K. Rajoriya, B. P. Panda, I. M. Mishra and K. L. Wasewar

Abstract
Adsorption isotherms of benzaldehyde from aqueous solutions onto granular activated carbon have been determined and studied the effect of dosage of granular activated carbon, contact time, and temperature on adsorption. Optimum conditions for benzaldehyde removal were found adsorbent dose γ ≈ 4 g l–1 of solution and equilibrium time t ≈ 4 h. Percent removal of benzaldehyde increases with the increase in adsorbent dose for activated carbon, however, it decreases with increase in benzaldehyde mass concentration. Adsorption capacity of activated carbon for benzaldehyde removal decreases with increase in temperature, the adsorbent showing the exothermic nature of adsorption. The adsorption of benzaldehyde by granular activated carbon followed pseudo-second order kinetics. Diffusion is not the only rate-controlling step. Adsorption equilibrium data were analyzed by Langmuir, Frendlich and Temkin isotherm equation using regression analysis. Temkin found to best represent the data for benzaldehyde adsorption onto granular activated carbon. Value of the change in entropy (ΔS°) and heat of adsorption (ΔH°) for benzaldehyde adsorption on activated carbon were negative. The high negative value of change in Gibbs free energy (ΔG°) indicates the feasible and spontaneous adsorption of benzaldehyde on granular activated carbon.

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Keywords
thermodynamics, equilibrium, kinetics, activated granular carbon, benzaldehyde, adsorption