Adsorption of diclofenac and triclosan in aqueous solution by purified multi-walled carbon nanotubes

Abstract

The ability of purified multi-walled carbon nanotubes (MWCNTs) to adsorb diclofenac and triclosan in aqueous solutions was examined by equilibrium, kinetic, and thermodynamic parameters. The results of SEM image, BET specific surface area, XRD, TGA, and FTIR spectra indicated that the characteristics of MWCNTs were improved after purification with nitric acid. Batch experiments illustrated that the removal efficiency of diclofenac and triclosan depended mostly on the MWCNTs dosage, temperature, ion concentration, pH, and initial concentration. The maximum adsorption capacity for diclofenac and triclosan under optimum conditions was 19.9 mg g-1 and 19.7 mg g-1, respectively. The equilibrium data showed that adsorption behavior of diclofenac and triclosan could be described more reasonably by the pseudo-second-order model. Thermodynamic simulation showed that the adsorption was fitted with Langmuir and Freundlich adsorption isotherm, and the thermodynamic parameters revealed the process to be exothermic and spontaneous. In addition, the adsorption behavior of MWCNTs in the binary solution was successfully predicted using the ideal adsorbed solution theory. Finally, the adsorption mechanism was discussed.