Photoreduction of nitrates from waste and drinking water

Abstract The photoreduction of nitrate ions was studied for the abatement of N-containing compounds from waste and drinking water. A new processwas developed in semibatch mode, aiming at maximum selectivity towards N 2. Different photocatalysts have been prepared with two different methods and their photocatalytic performance has been compared with commercial nanostructured TiO 2 (P25). TiO 2 has been prepared in nanosized form by using an innovative flame pyrolysis (FP) approach, and mesoporous TiO 2 was prepared by sol-gel method. Pd has been added to TiO 2 by post synthesis impregnation. The physical/chemical properties of the photocatalysts were studied by means of XRD, BET and UV-Vis spectroscopy. The results show that the flame pyrolysis procedure is a viable technique for the preparation of nanosized TiO 2 for this application, leading to ca . double conversion with respect to P25. Furthermore, the addition of a small amount of Pd (0.1 mol %), likely enhanced the lifetime of the photoproduced charges by electron trapping and resulted in higher conversion and selectivity toward N 2 . The best performance was obtained with Pd doped on TiO 2 (FP), with 13% conversion and ca. 27% selectivity, only, toward ammonia formation.