Preparation of photocatalytic nano-ZnO/TiO(2) film and application for determination of chemical oxygen demand.

A composite nano-ZnO/TiO(2) film as photocatalyst was fabricated with vacuum vaporized and sol-gel methods. The nano-ZnO/TiO(2) film improved the separate efficiency of the charge and extended the range of spectrum, which showed a higher efficiency of photocatalytic than the pure nano-TiO(2) and nano-ZnO film. The photocatalytic mechanism of nano-ZnO/TiO(2) film was discussed, too. A new method for determination of low chemical oxidation demand (COD) value in ground water based on nano-ZnO/TiO(2) film using the photocatalytic oxidation technology was founded. This method was originated from the direct determination of the Mn(VII) concentration change resulting from photocatalytic oxidation of organic compounds on the nano-ZnO/TiO(2) film, and the COD values were calculated from the absorbance of Mn(VII). Under the optimal operation conditions, the detection limit of 0.1mgl(-1), COD values with the linear range of 0.3-10.0mgl(-1) were achieved. The results were in good agreement with those from the conventional COD methods.