Construction Of Interfacial Chemical Bonds Of Titanium Dioxide And Its Photocatalytic Oxidation Of As(Ⅲ) In Water

With the rapid progress of industrialization,people have come to realize that the severe situation of the earth’s environmental problems has become one of the bottlenecks restricting sustainable development.Water heavy metal pollution is one of the major problems in environmental governance,and how to carry out the governance of water pollutants has aroused people’s thinking,while photocatalysis technology has attracted wide attention due to its efficient and green water treatment ability,providing application and practical significance for the solution of water heavy metal pollution.In this paper,the traditional efficient photocatalyst titanium dioxide is selected as the research object.Aiming at the low utilization rate of titanium dioxide to photogenerated carriers and light energy,the interface chemical bond between phases is constructed to achieve the modification of the classical photocatalytic material titanium dioxide by means of morphological regulation,metal material loading,non-metallic atom doping and other technical means.It is also applied to the photocatalytic oxidation of As(Ⅲ)in water.The main research results of this paper are as follows:To improve the transfer efficiency of titanium dioxide to photogenerated carriers,TiO2@Fe3O4 composite photocatalytic oxidation material was prepared by hydrothermal method.The Ti-O-Fe interface chemical bond between TiO2 and Fe3O4 was successfully constructed,which greatly promoted the transfer efficiency of photogenerated carriers.The prepared materials were used for photocatalytic oxidation of As(Ⅲ)in water.The results showed that Fe3O4,TiO2@Fe3O4(TiO2@Fe3O4-1%)photocatalyst containing 1%mass fraction could complete the oxidation of As(Ⅲ)(10,000 pg/L,40 mL)to As(V)with an oxidation rate of 100%in 4 min.After 5 cycles,the properties are good and the crystal structure remains unchanged.In addition,the photocatalytic oxidation performance of TiO2@Fe3O4 composite remains stable at different pH values.The results of electron para-magnetic resonance(EPR)showed that superoxide radical(·O2-)and hole(h+)were the main intermediates of arsenic photocatalytic oxidation system,and hydroxyl radical(·OH)had little effect on the oxidation system.According to the data analysis results,the possible mechanism of photocatalytic oxidation of As(Ⅲ)was further discussed.In order to further improve the photoutilization rate of TiO2,carbon doping in situ was studied on the basis of previous work.A series of characterization showed that the photocatalytic activity of TiO2 changed from a single ultraviolet wavelength to visible light excitation after carbon atoms were successfully doped in the TiO2 lattice,which improved the utilization rate of light energy.DFT calculation further confirms that the theoretical band gap of TiO2 can be effectively shortened by C-O-Ti bond.In addition,the successful construction of chemical bonds at the interface of C-O-Ti and Ti-O-Fe provides a way for rapid electron migration,which can effectively promote the separation rate between photogenerated electrons and holes,so As to improve the photocatalytic oxidation efficiency of As(Ⅲ).The results showed that the conversion of As(Ⅲ)(10,000 μg/L,40 mL)to As(Ⅴ)was completed within 12 min under visible light irradiation by C doped TiO2@Fe3O4-1%.C/TiO2@Fe3O4 has excellent reusable performance.After 6 cycles,it can maintain 100%photocatalytic oxidation efficiency for As(III)without changing the crystal structure,and can be completely recovered by magnets.In arsenic photocatalytic oxidation system,the remarkable photocatalytic performance is due to the synergistic effect of OH,·O2-and ·h+in the photocatalytic system,as well as the constructed C-O-Ti and Ti-O-Fe interfacial bonds.