Development Of Weak Visible Light Response TiO₂ Complex And Its Photocatalytic Degradation Of Organics In Seawater System

Nano-titanium dioxide(Ti02)has attracted extensive attention in environmental pollution control.It is an environmentally friendly semiconductor material that is non-toxic,harmless,easy to obtain,and stable in photocatalytic performance.However,in practical applications,although Ti02 has many advantages,its own defects still limit the large-scale use of it.It can only be excited by 5%of the ultraviolet light(wavelength<380 nm),and the photo-generated carrier recombination rate is high.Therefore,it is important to improve the properties of Ti02 by increasing its visible light utilization efficiency and suppressing photogenerated electron-hole recombination.In this paper,RGO-TiO2 composite photocatalyst with visible light response was prepared by adsorption phase reaction technique and solvothermal method,and modified by ion doping.The prepared composite photocatalysts were characterized by X-ray diffraction(XRD),Fourier transform infrared spectroscopy(FT-IR),transmission electron microscopy(TEM)and X-ray photoelectron spectroscopy(XPS).The photocatalytic performance of the composite photocatalyst was tested by using phenol as the target pollutant in the seawater system under the 10 W LED light irradiation.The main studies of this paper are as follows:(1)Reduced graphene oxide(RGO)-TiO2 composite photocatalyst was prepared by the adsorption phase reaction technique and the solvothermal method,using graphene oxide(GO)and tetrabutyl titanate as raw materials.The effects of different solvothermal temperatures on the structure and photocatalytic properties of the composites were investigated,the optimum solvothermal temperature for the preparation of the samples was determined to be 160 ?.The degradation rate of RGO-TiO2 composite photocatalyst to phenol was 42.7%after 300 min of visible light irradiation.(2)In order to improve the visible light catalytic performance of the compositC photocatalyst,I decided to dope the lanthanum ion(La3+)on the RGO-TiO2 composite photocatalyst and study its effect on the structure and photocatalytic activity of the composite.The experimental results show that La3+ doping causes lattice distortion of Ti02,forms Ti-O-La bonds and generates Ti3+ and oxygen holes,which inhibits the recombination of electron-holes and enhances the activity of the composite photocatalyst.When the doping amount of La3+ is 0.05%,the composite photocatalyst has the strongest activity.After 300 min of visible light irradiation,the degradation rate of phenol is 83.3%,which is about twice that of RGO-TiO2.(3)In order to further study the effect of ion doping on the RGO-TiO2 composite photocatalyst,two kinds of rare earth ions(Yb3+and Ce3+)and four metal ions(In3+?Fe3+?Cu2+ and Cd2+)were doped respectively to study the effects of different kinds,different ionic radii and different ion doping amounts on the structure and photocatalytic activity of the composite photocatalyst.The experimental results show that the proper amount of metal ion doping can cause lattice distortion of TiO2,produce Ti3+ and impurity defects,which reducing the electron-hole recombination rate and improving its photocatalytic performance.The order of activity of composite photocatalysts doped with different ions is Cd2+>In3+>Cu2+>La3+>Ce3+>Fe3+>Yb3+,which is consistent with the order of Ti3+ content in the composite photocatalyst.Among them,when the doping amount of Cd2+ is 0.05%,the visible photocatalytic activity of the composite photocatalyst is the highest,and the total degradation rate of phenol is up to 92.5%.(4)I decided to change the solvent used for solvothermal reduction to ethylene glycol to study the effects of different thermal reduction solvents on the structure and photocatalytic performance of ion-doped composite photocatalysts.As a reducing agent,the control ability of ethylene glycol for crystallization of Ti02 is weaker than that of ethanol.The order of activity of composite photocatalysts doped with different ions is Cu2+>Cd2+>La3+>Fe3+>In3+>Ce3+>Yb3+.The composite photocatalyst prepared by the thermal reduction of ethylene glycol is more active than that prepared by ethanol.