Removal of an anionic reactive dye from aqueous solution using functionalized multi-walled carbon nanotubes: isotherm and kinetic studies

Abstract

In this research, the adsorption process of Reactive Blue 19 (RB19) as an anionic dye onto functionalized multi-walled carbon nanotubes (f-MWCNTs) was studied. For this purpose, four parameters including agitation time, adsorbent dose, initial dye concentration, and pH were examined. N₂ adsorption isotherms and Fourier transform infrared spectroscopy were used to characterize f-MWCNTs. Four isotherm and four kinetic models including two diffusion models were applied to comprehensively investigate the RB19 adsorption using f-MWCNTs. It was found that the adsorption follows Langmuir and Temkin equilibrium models with a maximum adsorption capacity of 217.39 mg g⁻¹. The adsorption process best fitted to pseudo-second-order kinetic model and by applying diffusion models, the predominant rate-limiting step was found to be physisorption during the liquid film diffusion.

Keywords:

• Adsorption
• Anionic dye
• Multi-walled carbon nanotubes
• Isotherm
• Kinetics
• Diffusion models

Acknowledgments

The authors would like to thank Amirkabir University of Technology (AUT), Iran Nanotechnology Initiative Council (INIC), and Alborz Industrial Estates for financial support of this research.