Fabrication and Photoelectrocatalytic Degradation Alachlor under Visible Light of Titania Nanotubes
|School||Harbin Institute of Technology|
|Course||Environmental Science and Engineering|
|Keywords||TiO2 nanotube Visible light Photoelectrocatalytic oxidation Alachlor|
Because of low energy consumption, mild reaction conditions, simple operation and no secondary pollution, photocatalytic oxidation technology with TiO2 is outstanding among a lot of others advanced oxidation technologies. However, the Suspended TiO2 in the sewage treatment process is difficult to recover, while the surface area of the fixed state TiO2 photocatalyst is small, which limite the capacity of photocatalytic degradation of organic compounds. Meanwhile, the high rate of electron-hole pairs on the TiO2 surface and in the bulk phase, leading to a very low quantum efficiency, which restrains the practical application of TiO2 photocatalytic oxidation technology.To raise the specific surface area, titanium dioxide nanotube arrays were prepared by an anodic oxidation process with post-calcination. Through the coupling with electro-catalytic, the recombination between then and hole was reduced. The best impressed current and best applied voltage were confirmed by photoelectrocatalysis process.The preparation conditions of TiO2 nanotubes were optimized, mainly inspected the effects of anodizing voltage, anodizing time, temperature and calcined temperature to the surface morphology and photocatalytic degradation of alachlor. the optimal preparation conditions: anodizing voltage is 20V, anodizing 1h, the preparation temperature is 23℃and calcinated at 500℃. Compared the photocatalytic degradation activity of alachlor with TiO2 nanotubes and the TiO2 film which also prepared by anodic oxidation.Using scanning electron microscopy （SEM）, energy dispersive spectroscopy （EDS）, X-ray diffraction （XRD）, X-ray photoelectron spectroscopy （XPS）, specific surface area measurements （BET） and other methods, the surface morphology, crystal structure, surface composition, chemical forms and specific surface area of TiO2 nanotubes were analyzed.TiO2 thin film and TiO2 nanotubes were used to photocatalytic oxidize alachlor, which is endocrine disrupting chemical, and the photocatalytic activity of TiO2 nanotubes and TiO2 film was compared. The reaction of photocatalytic degradation by TiO2 nanotubes fitted the pseudo first order reaction model.The optimal applied current and the optimal applied voltage were determined by the degradation efficiency of alachlor with TiO2 film and TiO2 nanotubes, and the synergistic between the photocatalytic and electrocatalytic was confirmed. The photoelectrocatalytic degradation mechanism of alachlor by TiO2 nanotubes was studied. On one hand, the applied current or voltage forced the conduction band electron move to the cathode, on the other hand, the SO42- in electrolyte can be oxidized by strong valence band hole to S2O82- which can improve the degradation efficiency of alachlor. The photoelectrocatalytic degradation of alachlor by TiO2 nanotubes fitted the pseudo first order reaction model. Both photoelectrocatalytic degradation and electrocatalytic degradation of alachlor by TiO2 nanotubes were better than TiO2 film.The rules of·OH generation were studied when photoelectrocatalytic oxidized alacholor by using fluorescence. The experimental results show that: the content of·OH increases with the light irradiation intensity; when pH=4.6, the maximum content of·OH is reached; and it increases with the bias voltage, but decreases when the content of tert-butanol increases.