Preparation of magnetic carboxymethyl starch/graphene oxide hydrogel for adsorption of methylene blue

The magnetic composite hydrogel was prepared by using graphene oxide (GO), carboxymethyl starch (CMS) and Fe3O4 as raw materials via a facile one-step reaction route. Magnetic CMS/GO hydrogel was applied as an adsorbent for methylene blue (MB) and characterized by scanning electron microscopy, X-ray diffraction, Fourier-transform infrared spectroscopy, thermogravimetry and vibrating sample magnetometer. Kinetics, isotherm and thermodynamics of adsorption were investigated. The results show that the adsorption of MB onto the hydrogel was well-described by pseudo-second-order adsorption kinetic and Langmuir models, and it was a spontaneous thermal reaction. GO was uniformly dispersed in the hydrogel, which significantly improved the adsorption capacity and thermal stability of the hydrogel. In addition, the adsorbent showed high efficiency for the removal of MB with the maximum adsorption capacity of 622.71 mg/g at 293 K, and its removal efficiency had no significant reduction after five cycles of adsorption. Thus, magnetic CMS/GO hydrogel may be a promising adsorbent for the removal of MB from aqueous solutions in environmental pollution treatment.