Beta-cyclodextrin carbon microspheres by hydrothermal carbonization for malachite green adsorption

Abstract

This work was aimed at evaluating the adsorption characteristics of beta-cyclodextrin (β-CD) chars. Char was prepared by pyrolysis in a furnace at 550 °C, while spherical hydrochar was obtained through hydrothermal carbonization in a Teflon autoclave at 180 °C. Both chars are water-insoluble and were prepared without cross-linking agents. They were characterized for functional groups, thermal degradation, and surface morphology. The applicability of chars in adsorption was studied using malachite green solution at varying concentrations, contact times and temperatures. Hydrochar exhibits a better malachite green capacity of 18 mg/g. The adsorption rate and equilibrium data fitted well into pseudo-first-order and pseudo-second-order kinetics, and Langmuir and Dubinin–Radushkevich models, respectively. The thermodynamic parameters suggested that the removal process is spontaneous and endothermic in nature.