| It is a serious problem that water contamination caused by the heavy metals and organic dyes,because they brought negative influence of ecosystem and human health.Heavy metals,such as copper,chromium,cadmium,lead and so on are virulent which are released into the environment.However,they are only accumulated in the living body that cannot be degraded by the organisms.Organic dyes are toxic to aquatic organisms,some of them may be mutagenic and carcinogenic.Therefore,it will be a big damage to the environment and human health,if the sewage are treated and controlled loosely.Metal oxide/gaphene nanocomposites have attracted increasing attention due to large surface area,high number of active surface sites,low intraparticle diffusion rate and high chemical stability.Currently,to obtain high-quality metal oxides/graphene,some methods for the synthesis of metal oxides/graphene nanocomposites with control over the size,shape,structure,and properties have been developed.Compared with the traditional photocatalyst and adsorbent,metal oxide/graphene composites show a promising perspective in environmental application.Therefore,design and synthesis of the metal oxide/graphene nanocomposites with shape-controlled,high reaction activity and high photocatalytic/adsorption performance become one of the focus of this research.Then main contents for this paper carried out as follows:1.A novel TiO2/ZnO-NH2-reduced graphene oxide(TZ-a-RGO)nanocomposite was successfully prepared using a facile one-step hydrothermal method.The TZ-a-RGO was characterized by X-ray diffraction(XRD),Fourier transform infrared spectroscopy(FTIR),Transmission electron microscopy(TEM),Brunauer-Emmett-Teller(BET)surface area analysis and UV-vis absorption spectrophotometry to investigate its structural features.The TZ-a-RGO was used as a catalyst to remove methyl orange(MO)from wastewater,and the results indicated that this catalytic system has a good performance in terms of removal of MO.The adsorption experiments of the TZ-a-RGO followed the pseudo-second-order kinetic model,and the adsorption isotherms were accurately represented by the Langmuir model.The degradation of methyl orange(MO)by TZ-a-RGO fitted well with the Langmuir-Hinshelwood model,and MO removal was obtained through a synergistic effect of adsorption and photocatalysis.The photocatalytic rate of MO over the composites was as high as 8.2 and 3.2 times that over commercial P25(Degussa)and TiO2/ZnO,respectively.The potential photocatalytic mechanism for the TZ-a-RGO nanocomposite under UV was discussed.2.Introduction of α-MnO2 nanosheets to NH2-graphene(α-MnO2-NH2-RGO)to remove Cr6+ from aqueous solutionsThe planar structure of the designed α-MnO2-NH2-RGO hybrid were prepared and characterized and used to remove hexvalent chromium ions(Cr6+)in aqueous solution.The characterization of the novel adsorbent was carried out using the Fourier transform infrared spectrum(FT-IR),X-ray diffraction(XRD),Transmission electron microscope(TEM),Brunaouer-Emmett-Teller(BET).The Cr6+ adsorption efficiency was investigated as a function of the pH of Cr6+ solution,contact time and temperature.The results exhibited that the adsorption capacity depended on the pH strongly and the adsorption equilibrium data were best described by the Frenudlich isothermal model.The maximum sorption capacity towards Cr6+ was 371 mg/g.The kinetic adsorption was fitted to the pseudo-second-order kinetics model indicated that the adsorption mechanism is physical and chemical sorption on heterogeneous materials.The thermodynamic parameters were obtained and the results showed that the process of adsorption is spontaneous and exothermic.The adsorption capacity of α-MnO2-NH2-RGO can remain up to 81%after five cycles of usage.Consequently,the finds propose that α-MnO2-NH2-RGO could be used as an outstanding adsorbent for Cr6+. |
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