Photocatalytic Degradation of Methyl Orange by H2O2 Cooperated with Graphene Oxide Under Visible Light Irradiation

Graphene oxide(GO) was prepared by a modified Hummers method, and the morphology, composition and structure of the graphene were characterized by scanning electron microscopy(SEM) and Raman spectroscopy. The photocatalytic ability of GO and H2O2 composite reagents to degrade refractory organic wastewater which was represented by methyl orange(MO) was studied by changing the pH, light, and addition of graphene oxide. We also discovered that the photocatalytic effect of H2O2 improves a lot after cooperated with GO, when pH = 2, degradation rate increases 79.09%. When pH=3, the degradation rate of methyl orange can reach 99.45% under visible light irradiation after 48h. This study provides a new idea for remedying water polluted by refractory organics since it has so many advantages such as the dosage of GO is little, the cost of preparing GO by a modified Hummers method is low, and the hazardous waste is not produced. Introduction With the development of industry and living standard of people, the quantity of wastewater with complex constituents and structure is increasing[1, 2]. Many contaminants have stable chemical structure, even teratogenic, carcinogenic, mutagenic risks, consequently, even if they occur in the environment at very low concentration, it is also an enormous threat to the creature and environment after years of accumulation[3]. Fenton's reagent, a hybrid system consisting of H2O2 and Fe2+, can produce •OH which can degrade the pollutants with its powerful oxidization, shows its superiority in refractory organics treatment[4]. Based on traditional Fenton's reagent, the scientists tried a lot to develop Fenton-like techniques, such as photo-Fenton[5], electro-Fenton[6] sono-Fenton[7], microwave-Fenton[8] etc., catalyst is also improved and substituted, Choi et al[9] tested the photocatalytic activity of ZnO and Ag/ZnO with H2O2 addition by the degradation of rhodamine B (RhB) and methylene blue (MB), Oliveira et al[10] found that a reducing treatment with H2 can strongly modify the redox properties of an activated carbon, resulting in a higher decomposition of H2O2 and the oxidation of organics in water. Zhao et al[11] prepared a series of CuOx decorated ZnFe2O4 samples by a hydrothermal method and investigated it as a catalyst for the photocatalytic and Fenton-like degradation of Orange II. The most widely explored catalytic materials mainly concentrate on transition metals and metal oxides so far[12]. The use of metal, however, still suffer from disadvantages such as high cost, poor corrosion resistance in air, harm to the environment and easy to produce hazardous waste[13] and many metallic resources on earth are dwindling as a result of the excessive exploitation from the booming modern industries. Therefore, metal-free catalysts, especially carbon materials have attracted much attention recently because it is inexpensive, biocompatible, stable, sustainable, environmentally friendly and readily available[14]. Graphene is a flat monolayer of carbon atoms close-packed into a two-dimensional honeycomb lattice[15]. It is a promising nanomaterial with extraordinary physical and chemical properties such as the huge specific surface area, remarkable electrical, thermal and mechanical properties and graphene oxide has shown its superiority in the catalytic field[16]. In this work, graphene oxide (GO) was prepared by a modified Hummers