Reaction Conditions and Aqueous Washing Process: Implications for Graphene Oxide Production and Its Applications

The oxidation reaction of graphite with potassium permanganate in sulfuric acid has been widely discussed in the literature; however, its application on an industrial scale lacks a detailed methodological review that describes the interaction of variations in reaction conditions. This long-range study reviews the reaction conditions in addition to analyzing in detail the sample washing process; the objective is to understand the process of oxygen transfer to graphite sheets in order to adapt the reaction conditions according to the graphene oxide (GO) applications. The results of the systematic variations of the reaction conditions indicate that longer reaction times favor solubility because of a greater presence of C═O and O─C═O groups, the proportion of permanganate determines the homogeneity in the distribution of oxygenated groups, and it is demonstrated that the reaction is efficient at room temperature, avoiding damage to the sp2 structure of the carbon. From washing analysis, it has been determined that it is the water that transfers oxygen to the graphite during the washing process. This result indicates the importance of describing the washing process as part of the reaction itself and allows us to more precisely define the amount of water to use according to the needs of our product. Thus, from both results, the graphite oxidation process has been redefined considering the washing process, describing three stages: stage 1, primary oxidation; stage 2, ion removal; stage 3, main oxidation and sheet separation. The results of this study allow one to define the reaction conditions suitable for the use of the GO prepared.