Graphene oxide: Follow the oxidation mechanism and its application in water treatment

Graphene oxide was intensively researched, however, its mechanism of formation unclear. The reaction manner between the solid graphite and the liquid phase and how the oxidizing agent attack the graphite and how are different function groups formed, not clearly explained. In this study, we follow the formation of GO from precursor graphite (pr-G) as a function of the time. The obtained results showed that the reaction can stopped at any time, and the corresponding intermediate can be isolated, characterized and stored under appropriate conditions. The intermediates and the final product (GO) were characterized using optical microscopy, SEM, UV-Spectroscopy Raman, XRD, FTIR and EDS. Based on these results, a mechanism for GO formation is given. Further, the adsorption process of Methyl bleu, MB, and Crystal violet, CV, dyes from aqueous solution by the prepared GO were investigated under different conditions of dyes concentration, pH, GO dose, temperature and ionic strength. The adsorption kinetic data was found to fit pseudo-second order model for both MB and CV. Equilibrium data of the adsorption processes showed that adsorption of MB and CV is fitted to the Langmuir isotherm with q(e) 357.14 mgg(-1) for MB and 256.41 mgg(-1) for CV. The GO obtained after adsorption was characterized using XRD, FTIR and Raman which showed different spectra from pure GO. (C) 2018 Elsevier B.V. All rights reserved.