Highly enhanced adsorption of congo red onto graphene oxide/chitosan fibers by wet-chemical etching off silica nanoparticles

Graphene oxide/chitosan/silica fibers were prepared by a wet spinning technique. Silica nanoparticles were etched off from the graphene oxide/chitosan/silica fibers to produce graphene oxide/chitosan fibers with porous structure. The morphology and functional groups of the porous graphene oxide/chitosan fibers were characterized using scanning electron microscopy and Fourier-transform infrared spectroscopy, respectively. Adsorption experiments with the porous graphene oxide/chitosan fibers were performed based on various parameters, such as initial congo red concentration, solution pH, adsorbent dose and contact time. The Langmuir, Freundlich, Temkin and Dubinin-Radushkevich isotherm models were employed to discuss the adsorption behavior. The results indicated that the equilibrium data were perfectly represented by the Langmuir isotherm. The maximum adsorption capacity reached 294.12 mg/g. The kinetics data were analyzed using pseudo-first-order, pseudo-second-order, Elovich and intrapartide diffusion models and the pseudo-first-order model best described the adsorption of congo red onto the porous graphene oxide/chitosan fibers. (C) 2014 Elsevier B.V. All rights reserved.