Fabrication And Photoelectrocatalytic Degradation Alachlor Under Visible Light Of Titania Nanotubes

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 SO₄^2- in electrolyte can be oxidized by strong valence band hole to S₂O₈^2- 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.