Removal of methylene blue from aqueous solution by a solvothermal-synthesized graphene/magnetite composite

In this study, we have demonstrated a facile one-step solvothermal method for the synthesis of the graphene nanosheet (GNS)/magnetite (Fe3O4) composite. During the solvothermal treatment, in situ conversion of FeCl3 to Fe3O4 and simultaneous reduction of graphene oxide (GO) into graphene in ethylene glycol solution were achieved. Electron microscopy study suggests the Fe3O4 spheres with a size of about 200 nm are uniformly distributed and firmly anchored on the wrinkled graphene layers with a high density. The resulting GNS/Fe3O4 composite shows extraordinary adsorption capacity and fast adsorption rates for removal of organic dye, methylene blue (MB), in water. The adsorption kinetics, isotherms and thermodynamics were investigated in detail to reveal that the kinetics and equilibrium adsorptions are well-described by pseudo-second-order kinetic and Langmuir isotherm model, respectively. The thermodynamic parameters reveal that the adsorption process is spontaneous and endothermic in nature. This study shows that the as-prepared GNS/Fe3O4 composite could be utilized as an efficient, magnetically separable adsorbent for the environmental cleanup. (C) 2011 Elsevier B.V. All rights reserved.