Photo-catalytic inactivation of E. coli using stabilized Ag/S, N-TiO2 nanoparticles by fixed bed photo-reactor under visible light and sunlight

Abstract

Silver (Ag), sulfur (S), and nitrogen (N)-codoped titanium dioxide (TiO2) photo-catalysts were prepared by sol-gel method. The main compounds were tetrabutyl orthotitanate, 250 mg of thiourea, and 0.7, 1.4, and 2.8 mg of silver nitrate as the suppliers of sulfur, nitrogen, and silver, respectively. These photo-catalysts were stabilized on glass microbeads. The structural properties of synthesized photo-catalysts were investigated by X-ray diffraction, scanning electron microscopy, and energy dispersive X-ray. The optical activity of the photo-catalysts was evaluated by UV/Vis diffuse reflectance spectroscopy. Finally, the feasibility of inactivation of Escherichia coli, an index of water contamination, was investigated by the stabilized photo-catalyst in a fixed bed photo-reactor under visible light and sunlight. We observed that Ag (0.14 mg)/S, N-TiO2 caused 99.6% removal of E. coli at 1.5 × 108 CFU/mL initial concentration under visible light, but this photo-catalyst caused approximately 97% removal of E. coli under sunlight. These findings would help to better use the fixed bed reactor filled with stabilized photo-catalysts such as Ag/S, N-TiO2, as a multipurpose and efficient technique to disinfect waters highly contaminated with E. coli