(680d) TiO2-BASED PHOTOCATALYSTS IN UV and VISIBLE REGION: Study of Activity and Stability

Heterogeneous photocatalysis has emerged as a potential alternative for the degradation of organic pollutants in water. The TiO2 DP25 is the most active catalyst but it is limited to be used in the range of UV light. In order to make the DP25 active in the visible region, ion doping and coupling the DP25 with another photocatalysts have been tested. In this study, various catalysts were prepared using the sol-gel and wet impregnation techniques. Fe (III), Ni (III), and Ag (I) ions were used for the doping of DP25. AgBr was coupled with TiO2 using the deposition-precipitation method. Catalysts prepared by the sol-gel techniques and wet impregnation are tested in the UV region, while the AgBr/TiO2 catalysts are tested in the visible region. Both experiments were evaluated for the degradation of maleic acid in water. TiO2 + 5 ppm Fe catalyst has the higher activity in UV region but showed no activity in the visible region. On the other hand, AgBr/TiO2 catalyst was the most active in the visible region but showed lack of stability as it decomposed into Ag and Br2 while being irradiated. Thus, it is concluded that in order to utilize the AgBr/TiO2 catalyst under Vis radiation, it is necessary to find ways to make it stable under visible light. In this regard, it was found that AgBr/TiO2 catalyst could be stabilized for longer periods of time when the pH of the reacting solution was maintained at 2. A full characterization of the prepared catalysts is carried out to understand their structure and operational mechanism under the UV and Vis range to develop materials that are stable and active for longer reaction periods. This will allow the use of photocatalysts under both visible light and UV such as that naturally present in the sunlight.