Characterization of multi-walled carbon nanotubes and application for Ni²⁺ adsorption from aqueous solutions

Abstract

Multi-walled carbon nanotubes (MWCNTs) were used to remove Νi²⁺ from aqueous solutions. Batch experiments performed to examine the effects of initial Νi²⁺ solution concentrations, pH, and contact time on Νi²⁺ sorption process. MWCNTs were characterized by scanning electron microscopy, transmission electron microscopy, atomic force microscopy, micro-Raman spectroscopy, thermogravimetric analysis, and specific surface area (BET) techniques. The tested MWCNTs exhibit purity >95%, average diameter 20–30 nm, and specific surface area >150 m²/g. The results showed that 60–95% of Ni²⁺ was absorbed depending on the initial solution concentrations. As it is suggested by the distribution coefficient (k_d) values, increased initial Νi²⁺ solution concentrations resulted to lower Νi²⁺ adsorption intensity onto MWCNTs, while the total amount of Ni²⁺ that removed from the equilibrating solutions increased. The adsorption of nickel onto MWCNTs was significantly affected by the solution pH; higher Ni²⁺ adsorption was observed at pH > 6.0. According to the contact time experiments, the sorption process reached equilibrium at 60 min. This study suggests that MWCNTs can be utilized for the removal of nickel ions from aqueous solutions and that they can be a promising candidate adsorbent for environmental applications and wastewater treatment.

Keywords:

• Multi-walled carbon nanotubes (MWCNTs)
• Nickel
• Adsorption
• Electron microscopy (SEM—TEM)
• Atomic force microscopy (AFM)
• Micro-Raman spectroscopy
• Thermogravimetric analysis (TGA)

Acknowledgments

The authors gratefully acknowledge the Glonatech SA (www.glonatech.com) that produced and provided the multi-walled carbon nanotubes as well as for their support.

Notes

Presented at the 12th International Conference on Protection and Restoration of the Environment (PRE XII) 29 June—3 July 2014, Skiathos Island, Greece