Fabrication of three-dimensional porous β-cyclodextrin/chitosan functionalized graphene oxide hydrogel for methylene blue removal from aqueous solution

A three-dimensional porous beta-cyclodextrin/chitosan functionalized graphene oxide hydrogel (3D-GO/CS/beta-CD) was synthesized by a simple and facile chemical reduction method in the presence of sodium ascorbate which acted as a reducing agent, and its application as an adsorbent for MB removal was investigated. The unique 3D structure enabled the rapid reuse and recyclability of 3D-GO/CS/beta-CD without a complicated filtration system. The adsorbent was characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), Fourier transform infrared (FTIR) spectroscopy, Raman spectroscopy, X-ray diffraction (XRD), thermogravimetric analysis (TGA) and Brunauer-Emmett-Teller (BET) analysis, and the results of the characterization indicated the successful synthesis of 3D-GO/CS/beta-CD. The 3D-GO/CS/beta-CD showed an ultrahigh adsorption capacity (1134 mg/g) for MB. The investigation of the adsorption behavior demonstrated that the adsorption was well fitted with the pseudo-second-order model and Freundlich model. The simulation of the intra-particle diffusion model illustrated that both film diffusion and intraparticle diffusion were involved in the adsorption process. The thermodynamics analysis suggested that the adsorption process of MB onto 3D-GO/CS/beta-CD was spontaneous and endothermic. Furthermore, the regeneration study showed that the 3D-GO/CS/beta-CD can be reused in the wastewater treatment application. All these findings demonstrated that the 3D-GO/CS/beta-CD could be a cost-effective and promising adsorbent for MB removal from the aqueous solution.