Fabrication of Graphene-Based Xerogels for Removal of Heavy Metal Ions and Capacitive Deionization

Abstract

With a rapid increase of population, delivering clean and potable water to humans has been an impending challenge. Here, we report a green method for the preparation of graphene–chitosan–Mn₃O₄ (Gr–Cs–Mn₃O₄) composites, where Gr–Cs hydrogels are first prepared from the self-assembly of chitosan with graphene oxide (GO) nanosheets; then Gr–Cs–Mn₃O₄ composites are obtained by oxidizing Mn­(II) ions which are adsorbed by Gr–Cs hydrogels. The effects of pH and mass ratio of GO to Cs on sorption of different ions are investigated. Enhanced capacitive deionization performance of Gr–Cs–Mn₃O₄ composites was also demonstrated. The resultant Gr–Cs–Mn₃O₄ composites exhibit a hierarchical porous structure with a specific surface area of 240 m²/g and excellent specific capacity of 190 F/g, much higher than those of pristine reduced graphene oxide electrodes. Distinguished electrochemical capacity and low inner resistance endow Gr–Cs–Mn₃O₄ composites with outstanding specific electrosorptive capacity of 12.7 mg/g