Preparation of Graphene Oxide/Cellulose Composites with Microcrystalline Cellulose Acid Hydrolysis Using the Waste Acids Generated by the Hummers Method of Graphene Oxide Synthesis

The Hummers method is the most commonly used method to prepare graphene oxide (GO). However, many waste acids remain in the raw reaction mixture after the completion of this reaction. The aim of this study was to reuse these waste acids efficiently. In this study, microcrystalline cellulose (MCC) was directly dissolved in the mixture after the high-temperature reaction of the Hummers method. The residual acid was used to hydrolyze MCC, and the graphene oxide/microcrystalline cellulose (GO/MCC) composites were prepared, while the acid was reused. The effects of MCC addition (0.5 g, 1.0 g, and 1.5 g in 20 mL) on the properties of the composites were discussed. The structure, composition, thermal stability, and hydrophobicity of GO/MCC composites were characterized and tested by SEM, XRD, FTIR, TG, and contact angle tests. The results showed that MCC could be acid hydrolyzed into micron and nano-scale cellulose by using the strong acidity of waste liquid after GO preparation, and it interacted with the prepared GO to form GO/MCC composites. When the addition amount of MCC was 1 g, the thermal stability of the composite was the highest due to the interaction between acid-hydrolyzed MCC and GO sheets. At the same time, the hydrophobic property of the GO/MCC composite is better than that of the GO film. The freeze-dried GO/MCC composites are more easily dispersed in water and have stronger stability.