Superior adsorption of methyl orange by h-MoS2 microspheres: Isotherm, kinetics, and thermodynamic studies

A batch equilibrium system was used in this study to investigate the adsorption of methyl orange (MO) on hollow molybdenum disulfide (h-MoS2) microspheres. The effects of experimental conditions, such as the initial concentration, agitation time, solution pH and temperature, on the adsorption were examined. The adsorption of MO on h-MoS2 microspheres was unexpectedly ultrafast. Adsorption equilibrium was rapidly achieved in 10 seconds, and the maximum adsorption capacity for MO was 41.52 mg/g. The Langmuir and Freundlich models were used for determining the adsorption parameters. The results reveal that the Freundlich model fits well with the experimental adsorption data. Pseudo-first-order, pseudo-second-order, and intraparticle diffusion models were applied to determine the kinetics of MO ultrafast adsorption. The obtained results indicate that the experimental kinetics data of h-MoS2 microspheres are well explained by the second-order model. The obtained values of the thermodynamic parameters (ΔH0, ΔS0, and ΔG0) indicated that MO adsorption on h-MoS2 microspheres was an exothermic and spontaneous process. The thermodynamic parameters also confirmed that the MO adsorption is a chemical and physical adsorption process on the surfaces of h-MoS2 microspheres. The adsorption mechanism was further advanced by FT-IR. The findings of this study open an avenue for applying h-MoS2 microspheres for organic dyes removal from industrial wastewater streams.