Effective adsorption of toluene and benzene on coconut activated carbon modified with carbon nanotubes: kinetics, isotherms and thermodynamics

The paper describes the adsorption of toluene and benzene on a new sorption material—coconut activated carbon (AC) modified with carbon nanotubes. The new material was characterized using Raman spectroscopy, scanning and transmission electron microscopy, X-ray diffractometry and FTIR. Also, the parameters of the porous space and the specific surface area were determined. The adsorption capacity for toluene and benzene was 123.53 and 84.92 mg g−1, respectively, the contact time was 60 min. The kinetic data were described using intraparticle diffusion, and the results of isothermal studies were described using the Langmuir, Freundlich, and Dubinin-Radushkevich equations. It was found that the adsorption of toluene and benzene considered Weber-Maurice model, that conform to a diffusion with fluid phase film resistance. In addition, the physical nature of adsorption is confirmed by the values of free energy (E = 6.92 and 8.41 kJ moL−1 for benzene and toluene, respectively). According to a thermodynamic study, the Gibbs energy values for nanomodified AC were − 16.32 kJ moL−1 for benzene and − 33.33 kJ moL−1 for toluene, which corresponds to the range of values for physical sorption. Thus, the material can be considered as a promising adsorbent for removing organic pollutants from aqueous media.