Study of adsorption properties of anionic dyes on graphene oxide/chitosan composite porous microspheres

Dyes wastewater produced during leather processing caused serious environmental pollution. Anionic dyes are always vital crisis in waste treatment. Removal of anionic dyes from tannery wastewater before their discharge into the environment is important for health and environment safety. The use of low-priced and biodegradable adsorbents could be a good method to minimize the environmental impact caused by dyes effluents. In this study, novel porous composite microspheres composed of graphene oxide and chitosan (GO/CS) were prepared. The morphology of the GO/CS porous composite microspheres were characterized using scanning electron microscopy. GO/CS porous microspheres were applied as adsorbent to remove the anionic dye in wastewater. The adsorption experiments were performed based on various parameters, such as initial anionic dye concentration, temperature, solution pH and contact time. The Langmuir and Freundlich isothermal models were employed to discuss the adsorption behavior. The results indicated that the anionic dyes adsorption by GO/CS porous microspheres could be described by Langmuir isothermal model. The maximum adsorption capacity reached 255 mg/g (at pH 3, 30°C). The kinetics data were analyzed using pseudofirst-order and pseudo-second-order, respectively. It was found that the pseudo-second-order model described the anionic dyes adsorption by GO/CS porous composite microspheres very well. Thermodynamic studies indicated that the adsorption of anionic dyes on GO/CS porous microspheres was an exothermic process. The present results show that the graphene oxide/chitosan composite porous microspheres can serve as a promising bio-adsorbent for the removal of anionic dyes from wastewater.