Use of rice husk ash as a potent adsorbent of malachite green: kinetic and equilibrium studies

Abstract

In this work, an adsorbent was prepared by calcination of rice husks and used as a membrane to remove malachite green contained in an aqueous solution. The synthesized adsorbent was characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM) and Fourier Transform Infrared (FTIR) spectroscopy. The kinetics and equilibrium of malachite green adsorption on rice husk ash was studied in batch. The effects of contact time and initial concentration were examined. The results show that the maximum adsorption capacity of malachite green by calcined rice husks is 8.58 mg/g for an initial concentration of 60 mg/L after an equilibrium time of 90 min. Langmuir, Freundlich, and D-R models were used to describe the adsorption isotherms. It was found that the Langmuir model perfectly describes the adsorption equilibrium with its correlation coefficient close to unity. This implies a monolayer adsorption of malachite green. The adsorption kinetics was modeled using the pseudo first order, pseudo second order and Elovich models. The pseudo-second order model better describes the adsorption kinetics of malachite green by rice husk ash. These results show that rice husk ash is a suitable adsorbent for the removal of malachite green in aqueous solution.