| The photocatalytic reaction refers to a process in which the photon energy can be utilized by photocatalyst to promote the synthesis or decomposition of the compound under the irradiation of light,while there was no any change in photocatalyst.With the help of Photocatalysts,the reactions,which is supposed to occur under hash conditions,also can happen under the mild conditions.Ti O2powder is the most widely used photocatalyst with abundant resources,good chemical stability,high photocatalytic activity,low cost,no toxicity and no pollution.However,the defect of agglomeration and the difficulty of separation hindered its recycling and increased the cost of its application indirectly.Therefore,the modification of Ti O2has become a new research hotspot in recent years.The loaded Ti O2had no shortcomings that Ti O2power had,for example,Ti O2power was easy to drain and difficult to recycle and reuse in the application process.But a large number of studies have shown that the supported Ti O2has the disadvantages of narrow absorption band,low quantum yield,low solar energy utilization and so on,which reduced the efficiency of the catalyst.The surface hybridization of conjugated molecules can improve the conductivity and the light utilization efficiency,which is an effective method to compensate for the shortcomings of supported Ti O2catalysts.In this study,Ti O2/hollow glass microbeads（HGM）and Ti O2/reduced graphene oxide（RGO）/HGM were prepared by modified hydrothermal synthesis.The morphology,crystal structure and optical properties of the two catalysts were characterized by using scanning electron microscopy（SEM）,energy dispersive spectroscopy（EDS）,X-ray diffraction（XRD）,BET method,X-ray photoelectron spectroscopy（XPS）,fluorescence analysis（PL）,ultraviolet-visible absorption spectroscopy（UV-Vis）and other technologies.Then the refractory pollutant Rhodamine B（Rh B）was used as the target pollutant,and photocatalytic degradation performance and the reutilization performance of Ti O2/HGM and Ti O2/RGO/HGM were investigated systematically.In addition,the effects of graphene content,reaction pressure and reaction time on photocatalytic efficiency were investigated.Finally,the principle of adsorption and degradation of Rh B was studied.The main findings are as follows:（1）Graphene oxide（GO）was prepared by the modified Hummers method,and then GO was successfully loaded onto HGM by mechanical stirring.The GO/HGM was mixed with titanium dioxide precursor,and the mixture was poured into the reactor to synthetic Ti O2/RGO/HGM composite catalyst under high temperature and high pressure by improved hydrothermal method.The results showed that GO can be reduced to RGO in the hydrothermal process with high temperature and pressure;Ti O2,RGO and HGM formed the spatial structure relationship from outer to inner encapsulation;The loaded Ti O2particles of surface were nanometer anatase,and the diameter distribution is uniform,about 13nm;The forbidden band width was 2.49 e V,which was lower than the band gap width of P25 Ti O2and Ti O2/HGM,and the absorption intensity in the ultraviolet region is obviously increased,and the absorption edge occurs red shift.（2）Ti O2/HGM as a catalyst,the degradation rate of a certain concentration of Rh B was 93.01%,and the degradation efficiency of the same concetration of Rh B was99.41%when Ti O2/RGO/HGM was the catalyst.After repeated use of Ti O2/RGO/HGM composite catalyst,the photocatalytic degradation rate of Rh B can still reach 88.34%.（3）The preparation conditions of the composite catalyst that had the optimal catalytic activity was obtained:GO（RGO）loading was 3%,pressure was 3.0 MPa,and reaction time was 10.0 h.Under this condition,the photocatalytic degradation was the best,and the Rh B removal rate was 99.41%.（4）The degradation mechanism of Ti O2/RGO/HGM composite catalysts shows that the interaction between pollutants and catalysts includes two stages of adsorption and photocatalysis.Adsorption:the adsorption kinetics of Rh B by Ti O2/RGO/HGM composite catalysts accorded with quasi-secondary reaction kinetics equation,and the equilibrium adsorption adsorption Qe was 1.52mg/g.The adsorption process of Rh B by composites is in line with the Freundlich adsorption isotherm model.According to the adsorption isotherm model,the maximum adsorption capacity of Ti O2/RGO/HGM composite catalyst for Rh B is 11.04mg/g,which is due to the largeπbond in the structure of Ti O2/RGO/HGM composite and the static electricity with Rh B molecule.These promote the adsorption of Rh B by the composite.Photocatalysis:the photocatalytic degradation efficiency could be inhibited by the isopropanol and p-benzoquinone.After adding isopropanol and p-benzoquinone respectively during the experiment,the degradation efficiency decreased to 88.63%and 73.65%,which indicates that both·O2-and·OH play a role in photocatalytic degradation,and·O2-is the main active material,and·OH plays a minor role. |
