Adsorption of Cu(II) on oxidized multi-walled carbon nanotubes in the presence of hydroxylated and carboxylated fullerenes.

Jing Wang,Zhan Li,Lei Wang,Yuanlv Ye,Fuqiang Liu,Peng Liu,Wei Qi,Liansheng Wu,Wangsuo Wu,Shicheng Li

doi:10.1371/journal.pone.0072475

Abstract

The adsorption of Cu(II) on oxidized multi-walled carbon nanotubes (oMWCNTs) as a function of contact time, pH, ionic strength, temperature, and hydroxylated fullerene (C60(OH)n) and carboxylated fullerene (C60(C(COOH)2)n) were studied under ambient conditions using batch techniques. The results showed that the adsorption of Cu(II) had rapidly reached equilibrium and the kinetic process was well described by a pseudo-second-order rate model. Cu(II) adsorption on oMWCNTs was dependent on pH but independent of ionic strength. Compared with the Freundlich model, the Langmuir model was more suitable for analyzing the adsorption isotherms. The thermodynamic parameters calculated from temperature-dependent adsorption isotherms suggested that Cu(II) adsorption on oMWCNTs was spontaneous and endothermic. The effect of C60(OH)n on Cu(II) adsorption of oMWCNTs was not significant at low C60(OH)n concentration, whereas a negative effect was observed at higher concentration. The adsorption of Cu(II) on oMWCNTs was enhanced with increasing pH values at pH < 5, but decreased at pH ≥ 5. The presence of C60(C(COOH)2)n inhibited the adsorption of Cu(II) onto oMWCNTs at pH 4–6. The double sorption site model was applied to simulate the adsorption isotherms of Cu(II) in the presence of C60(OH)n and fitted the experimental data well.

Highlights

Carbon-based nanomaterials have been widely studied [1] as a new material with special mechanical, electrical, optical, catalytic, magnetic and photon sensitive properties
Gao et al [9] studied the removal of nickel, copper, zinc, and cadmium from multi-component solutions by the oxidized multi-walled carbon nanotubes indicating that the significant factors are surface features, ion exchange, and electrochemical potential
It can be discerned that C60(OH)n particles are heterogeneously attached to the surface of oxidized multi-walled carbon nanotubes (oMWCNTs)

Summary

Introduction

Carbon-based nanomaterials have been widely studied [1] as a new material with special mechanical, electrical, optical, catalytic, magnetic and photon sensitive properties. Where qe (mg/g) represents the adsorption amount of the metal ions in the unit mass of oMWCNTs; ce (mg/L) is the equilibrium aqueous concentration; KF and n are the absorption capacity and strength in the Freundlich equilibrium constants, respectively.

Results

Conclusion