Photo-catalytic activity and life time of the TiO2 nano-particles

Titanium dioxide nano-particles (for example, P-25, Germany, Degussa) have been internationally used as an effective photo-catalyst for many years. In this paper, characterization of P-25, photo-degradation ability as well as its life time has been systematically studied by employing methyl orange as a model pollutant. Many factors such as the pH value, pre-treatment have been investigated. Just like other nanometer-sized or ordinary Anatase TiO2, the catalyst performs better at an optimal pH value. Pre-treatment of the catalyst also enhances the photo-catalytic ability. And the P-25 have shown rather good life time. The degradation products have been characterized by UV, mass and Raman spectrum. It is found that although the P-25 photo-catalyst has shown excellent decolourization ability, it is still difficult to degrade the methyl orange into small molecule, such as CO2 and H2O. Low-power ultraviolet lamps (9W, 254nm) have been used throughout. A comparison experiment has been carried out under natural sunlight, and the results have shown that natural sunlight (With temperature below 10degreesC) could provide even more energy than that of the adopted ultraviolet lamp, which have proved P-25 a rather promising photo-catalyst for practical application in environment field under natural surrounding. The obtained results may serve as a valuable reference for the evaluation and preparation of high quality TiO2 photo-catalyst.