TiO₂/graphene Nano-composite As A Photocatalyst For Dye Wastewater Treatment

Our country is the largest in the world of dye production and consumption. Dyesare widely used in textile, cosmetics and other industries. Effluent from these industrieshas high content of organic pollutants and salts, and its disposal become difficulty ofindustrial wastewater due to the high toxicity, high chemical oxygen demand (COD),deep colour and poor biodegradability. The TiO2photocatalysis degradation technologyis an effective way to deal with the dye wastewater. In this study, graphene was preparedby the oxidation-dispersion-reduction method, and was used to modify commercial TiO2(P25) to prepare TiO2/graphene composite photocatalyst. The nanocomposites werecharacterized using HR-TEM, XRD, N2adsorption/desorption analyzer, UV-Vis DRSand TGA. The adsorption and photocatalytic degradation performance of the compositefor dyes in aqueous solution were studied, and the optimal experimental conditions weredetermined.The conclusions of this experimental study were summerized as follows:1. Graphite oxide (GO) was prepared through modified Hummers’ method. Thengraphite oxide was ultrasonically exfoliated to achieve graphene oxide dispersion. Afteradding P25into the dispersion, the final TiO2/graphene composite was obtained by ahydrothermal process in which the reduction of GO and the loading of P25on thegraphene sheets were achieved.2、The TiO2/graphene composite was mesoporous. The specific surface area of thecomposite has a significant increase than TiO2, and the surface area of theTiO2/graphene composite increased with the increasing of graphene ratio. The additionof graphene not only increased the light absorption in the visible region, but alsoimproved the absorption of UV light. Calculated through the Kubelka-Munk equation,we can see that the band gap energy of P25is narrowed with the introduction ofgraphene.3. The TiO2/graphene composite exhibits perfect adsorption towards MB dye thanpure TiO2, and the adsorption ability of the composite increased with the increasing ofgraphene ratio in the composite. The adsorption capacity of P25-10%GN for MB dyewas calculated to be50mg/g through the adsorption isotherm.4. Photocatalytic degradation experiments indicated that all of the TiO2/graphene composite photocatalysts show enhanced photocatalytic degradation of RBk5comparedto P25. The RBk5removal efficiency after irradiated by a light source of UV365nm for100min can be above95%when the optimum conditions are initial RBk5concentration=10mg/L, catalyst dosage=0.4g/L, solution pH=3and the temperaturewas25°C.5. The RBk5removal by TiO2/graphene composite followed the pseudo first-orderkinetics model with a correlation coefficient of0.98. It can be seen through the kineticanalysis that the best graphene ratio in the composite was1%.