Oxidized multiwalled carbon nanotubes as efficient adsorbent for bromothymol blue

Abstract

In this work, an efficient adsorption system for the removal of bromothymol blue (BTB) from an aqueous solution using oxidized multiwalled carbon nanotubes (MWCNTs-COOH) has been described. The influence of effective variables such as solution pH, contact time, initial BTB concentration, amount of MWCNTs-COOH, and temperature on the adsorption efficiency in batch system was examined while BTB content was determined via UV-Vis spectrophotometer. Among different kinetic models (pseudo-first-order, pseudo-second-order, intra-particle diffusion, and Elovich model), experimental data of the removal process well fitted with the pseudo-second-order kinetic model with a high correlation coefficient. Evaluating the fitness of experimental equilibrium data by various conventional isotherm models including the Langmuir, Freundlich, and Tempkin models (based on considering R ² value as criterion) show the applicability of the Langmuir model for the interpretation of experimental data with a maximum adsorption capacity of 55 mg g⁻¹ of adsorbent. Thermodynamic parameters (Gibb's free energy, entropy and enthalpy) of adsorption show that the adsorption process has endothermic nature.

Keywords:

• adsorption
• bromothymol blue
• carboxylic derivative multiwalled carbon nanotubes
• adsorption isotherm
• thermodynamics and kinetics of adsorption

Acknowledgments

The authors express their appreciation to the Graduate School and Research Council of the University of Yasouj for financial support of this work.