Correlation between the adsorption ability and reduction degree of graphene oxide and tuning of adsorption of phenolic compounds

Graphene oxide (GO) was prepared with a modified Hummers method and then reduced to different reduction degrees by using hydrazinehydrate. The obtained GO and reduced GO (RGO) were characterized. It was found that the reduction removed most of the oxygencontaining functional groups on the surface of GO. By using naphthalene as a probe, the interaction between RGO and organic molecules was evaluated with NMR. It was confirmed that the reduction of GO increased significantly the interaction between the IC system of graphene and the II unit of organic molecules. The thermodynamic analysis indicated that the adsorption was a spontaneous, exothermic and entropy-decreasing process. It was observed that the adsorption capacities were generally increased with increasing the reduction degree of GO. The chemical structures of phenolics also affected their adsorption on RGO. The adsorption of the phenolics on RGO was enhanced by introducing electrondonating and withdrawing functional groups on the benzene ring. Depending on the chemical structures of phenolics, the surface reduction of GO to RGO-1 significantly increased the adsorption capacity for phenolics by a factor as large as 235%. A possible adsorption mechanism and correlation between the adsorption ability, reduction degree of GO and chemical structures of phenolics was discussed. (c) 2013 Elsevier Ltd. All rights reserved.