Adsorption of dyes on carbon nanomaterials from aqueous solutions

Abstract

The removal of methylene blue (MB), a cationic dye and orange II (OII), an anionic dye, from aqueous solution by using carbon nanomaterials as multiwalled carbon nanotubes (MWNTs) and carbon nanofibers (CNF) as adsorbents was studied in batch experiments. The effect of pH, temperature and surface modification of adsorbent on the removal of MB and OII was also investigated. The removals of OII and MB by adsorption on MWNT were maximum at pH 3.0 and pH 7.0, respectively. However, in the case CNF was employed as adsorbent, the optimum values of pH were 9.0 and 5.0 for OII and MB, respectively. Langmuir and Freundlich isotherms are applied to fit the adsorption data of both dyes. Equilibrium data were well described by the typical Langmuir adsorption isotherm. Overall, the study demonstrated that MWNTs and CNFs can effectively remove cationic and anionic dyes as MB and OII from aqueous solutions under these experimental conditions.

Keywords:

• Adsorption
• cationic and anionic dyes
• multiwalled carbon nanotubes
• nanofibers
• wastewater

Acknowledgments

The authors gratefully acknowledge the financial support from Ministerio de Educación y Ciencia by CONSOLIDER Program through TRAGUA Network CSD2006-44, CTQ2008-02728 and by Comunidad de Madrid through REMTAVARES Network S2009/AMB-1588. M.M.M wishes to thank Ministerio de Educación y Ciencia for the financial support to her Ph D Grant (FPU AP2007-01198).