Graphene oxide with different oxygen content produced from natural and synthetic graphite sources for methylene blue sorption

Graphene oxide (GO) is of great interest due to its unique structure and properties and potential applications, including water purification. In this work, we report the synthesis of GO samples with different oxidation degree from two different sources of graphite using Hummers method. Natural flake graphite with a high degree of crystallinity, and synthetic fine powder graphite were used. All produced materials were characterized by CHNS analysis, X-Ray Diffractive analysis (XRD), Fourier Transform Infrared Spectroscopy (FTIR), Raman spectroscopy, Scanning Electron Microscopy (SEM) and Transmission Electron Microscopy (TEM). It was shown that the oxidation process for natural and synthetic graphite sources proceeds in different ways. The factors, affecting for the structure and properties of GO are the degree of crystallinity and the lateral size of the graphite flakes. The sorption activity of underoxidized, normally oxidized and overoxidized GO was compared toward the methylene blue (MB) dye in aqueous solution. The most efficient sorption was registered for GO produced from synthetic graphite with the use of 2.0 and 4.5 wt. eq. KMnO4. The sorbents removed 94 % and 100 % of MB from the solution, respectively, in approximately 10 min. Our results reveal that the structure and sorption properties of GO can be tuned by varying the oxidation degree as well as the graphite source, which may open the way to new developments in the GO-based materials applications.