The preparation of TiO2 nanometer photocatalyst film by a hydrothermal method and its sterilization performance for Giardia lamblia

The photocatalytic property of TiO2 is utilized to sterilize the Giardia lamblia in an aqueous solution in this study. The TiO2 colloidal solution used for the film was prepared by the modified hydrothermal method and it was directly coated on a UV-lamp, which was set up using a photoreactor manufactured in our laboratory. The TiO2 film was very stably attached to the UV-lamp, and it was transparent until 5-time coating. The size of the TiO2 particle in the film was distributed around 20–30 nm and the film thickness was about 200 nm per 1-time coating. The G. lamblia cell was just partially damaged under UV-irradiation without a TiO2 photocatalyst, but the dead cell became very small and the dead body finally disappeared with an increase in the intensity of UV-irradiation after 2 h. In addition, under the TiO2/UV-irradiation system, the sterilized (dead) rate of G. lamblia was very fast. The sterilizing power increased at lower pH in the initial step, but it rather increased at a higher pH in the final step. And the sterilization of G. lamblia was very sensitive to the temperature, and resulted in an increase in the sterilized rate at higher temperatures. On the basis of these experimental observations, it can be concluded that TiO2 photocatalyst under UV-irradiation could be adopted as one of the sterilization modalities for the G. lamblia.