N-Nitrosodiethanolamine Degradation in Water by Ag/TiO2 and Ag/SiO2 Under Natural Solar Light

On 304 stainless steel substrates, two combined systems based on silver particle semiconductors, Ag/TiO2 and Ag/SiO2, were formed. Such systems were applied in the photocatalytic degradation, profiting from sunlight, of nitrosamines, which are highly toxic substances, specifically N-Nitrosodiethanolamine. The synthesis of TiO2 and SiO2 was carried out by the sol–gel method with co-precipitation of Ag metallic particles, adding a quaternary-ammonium-based ionic liquid as a reducing agent. The photocatalysts were characterized by scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS) and X-ray diffraction (XRD), confirming the integration of anatase-phase TiO2 and amorphous-phase SiO2 and the Ag cubic structure. The band gap width was determined by means of the Tauc graphical method, finding 1.7 eV and 1.8 eV for SiO2 and TiO2, respectively. The photocatalytic evaluation occurred under direct sunlight irradiation, achieving degradation efficiencies above 98% during the first 30 min; in addition, organic matter was quantified through the chemical oxygen demand (COD) technique.