Nitrogen, Sulfur Modified Nanometer Titanium Dioxide Photocatalytic Degradation Of Organic Wastewater

In recent years, heterogeneous semiconductor photocatalysis gradually becomes a popular technique. Among of them, titanium dioxide (TiO₂) has been proved to be the most suitable photocatalyst for widespread environmental applications because of its strong oxidizing power, non-toxicity and long-term stability. However, the photocatalysis widespread technological use with TiO₂ is impaired by its wide band gap (3.2eV), which requires ultraviolet irradiation for photocatalytic activation. If the photocatalytically active region is expanded to the visible light region, sunlight or rays from artificial sources can be used more efficiently.In this work, N,S-comodified TiO₂ powders were prepared with tetrabutyl titanate and L-cystine via sol-gel method at room temperature. The as-prepared TiO₂ powders were characterized with X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), surface photovoltage spectroscopy (SPS), UV–Vis diffuse reflectance spectra (DRS), infra-red spectrometry (IR). From IR spectrum, S=O peaks (about 989cm-1, 1047cm-1, 1137cm-1, 1237cm-1) and N-H peak (1401cm-1) were observed.Corresponding to IR results, nitrogen (399.8eV, 401.8 eV) and sulfur (168.8ev) were found in XPS spectrum, which can attribute to O-Ti-N, Ti-N-O and SO42-, respectively. The results of DRS showed that the as-prepared TiO₂ powders exhibited a stronger absorption in the UV-Vis light region and an obvious red shift of absorption edge due to N,S-codoping.The photocatalytic activity was evaluated for the photocatalytic oxidation of Rhodamine B under UV light and daylight irradiation, respectively. The photocatalytic activity of the as-prepared N, S-co-doped TiO₂ powders in the ultraviolet light was kept (81%, 1h). Simultaneously, its photocatalytic activity (380nm⁶30nm, 77%, 1h; 470nm⁸00nm, 75%, 1h) in the visible light. The immobilized photocatalyst film were prepared with PTFE as adhesives. The optimal ratio of photocatalyst and PTFE was 4:1, and the optimal loading content was 37.5 mg/cm2 during the preparation of immobilized photocatalyst film. The photocatalytic activity of immobilized photocatalyst film was as strong as powder in suspension system whatever under UV or Vis, The photocatalytic activity of catalyst doesn't decrease because of loading.