Kinetics, Equilibrium, and Thermodynamics of Methyl Orange Adsorption onto Modified Rice Husk

Abstract

In this present research, rice husk was modified using a cationic surfactant cetyltrimethylammonium bromide (CTAB) and used as an adsorbent (MRH) to remove methyl orange dye (MO, anionic dye) from aqueous solution. A series of experiments were carried out in a batch process to determine the influences of different parameters such as pH, contact time, initial concentration of adsorbate and adsorbent dose. The kinetic data obtained from different batch experiments were analyzed employing pseudo-first-order, pseudo-second-order, Elovich and intra-particle diffusion model equations. The equilibrium adsorption data were analyzed by Langmuir, Freundlich, Temkin and Dubinin-Radushkevich (D-R) isotherm models. The results show that pseudo-secondorder kinetic model and Freundlich adsorption isotherm model achieved better fit with the experimental data. The percent adsorption and equilibrium adsorption capacity (qe) were increased with the increasing amount of adsorbent and initial concentration of dye, respectively. Thermodynamic parameters such as Gibbs free energy change (ΔG), enthalpy change (ΔH) and entropy change (ΔS) were calculated and the results showed that the adsorption was spontaneous and exothermic.