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

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 m(2)/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.