High-Speed and High-Capacity Removal of Methyl Orange and Malachite Green in Water Using Newly Developed Mesoporous Carbon: Kinetic and Isotherm Studies

Abstract

A novel mesoporous carbon nanostructured material was prepared and characterized by scanning electron microscopy, transmission electron microscopy, Raman spectroscopy, thermogravimetry, and X-ray diffractometry. The material demonstrated high-speed and high-adsorption capacities of 827.5 and 2484.5 mg g–1 for methyl orange (MO) and malachite green (MG) dyes in 10 min. The kinetic data were fitted to pseudo-first- and pseudo-second-order, external and intraparticle diffusion, and Elovich models, whereas the isotherm data were adjusted to the Langmuir, Freundlich, Temkin, Dubinin–Radushkevich, and Langmuir–Freundlich isotherms (Sips). It was found that MO and MG adsorption was limited by chemical interactions and mixed diffusion. Besides, the physical process was elucidated through free energy values (E = 2.56 and 0.049 kJ mol–1 for the MO and MG, respectively). Methyl orange adsorption mostly occurred through ion exchange and electrostatic interactions, and at lower MO concentrations, through chemical interactions and surface complexation as well. Malachite green adsorption took place only on lower-energy sites. Thus, it can be concluded that the adsorbent proposed herein possessed high-speed and high-adsorption capacity. Therefore, it can be considered as promising in removing the reported dye pollutants.