Multiwall carbon nanotubes decorated on calcined eggshell waste as a novel nano-sorbent: Application for anionic dye Congo red removal

Abstract

In this study multiwall carbon nanotubes (MWCNTs) was decorated on calcined eggshell (CES) to obtain a novel and low cost nano-sorbent for removal purposes. The MWCNTs/CES was prepared by a simple hydrothermal method and was characterized by X-ray powder diffraction, scanning electron microscopy and zeta potential measurements. Removal efficiency of the nano-sorbent was evaluated using anionic Congo red dye as a sample pollutant. The experiments were carried out in a batch system to optimize operation variables such as adsorbent dosage, Congo red concentration, solution pH and contact time. Langmuir, Freundlich, Tempkin and Dubinin–Raduskovich adsorption isotherm models were studied and the experimental results were addressed by Langmuir isotherm model. The maximum adsorption capacity was 136.99mgg−1, indicating high potential of MWCNTs/CES in the adsorption of Congo red. The adsorption kinetics was studied with the pseudo-first-order, pseudo-second-order, Elovich and intraparticle diffusion models. The thermodynamic parameters indicated that the adsorption of Congo red on the MWCNTs/CES was an exothermic and spontaneous process. Based on experimental results, MWCNTs/CES exhibit improved adsorption performance in comparison with non-treated eggshell (NES) and CES.