Adsorption of methylene blue on activated carbon fiber prepared from coconut husk: isotherm, kinetics and thermodynamics studies

Abstract

The adsorption of methylene blue (MB) on activated carbon fiber (ACF) and granular activated carbon (ACG) was studied in a batch system. The effects of initial concentration, agitation time, solution pH, and temperature were examined. Adsorption isotherms were described using both the Langmuir and Freundlich models. It was found that the Langmuir model fits well with the experimental data. The pseudo-first-order, pseudo-second-order, and intra-particle diffusion models were used to examine the kinetics data. The results obtained showed that empirical kinetics data of both ACF and ACG were only well described by the second-order model. It was observed that the ACF has adsorption performance higher than that of ACG. Adsorption thermodynamics parameters were estimated and their values indicated that the adsorption of MB on ACF and ACG were endothermic and spontaneous processes. Thermodynamic results also indicate that the adsorption of MB on both adsorbents is by chemical interaction.

Keywords:

• Isotherm
• Kinetics
• Thermodynamics
• Coconut husk fiber
• Activated carbon fiber
• Methylene blue

Acknowledgments

This research was supported by the University of Malaya through a Postgraduate Research Grant PV035-2011A, for which the authors are very grateful.