Inactivation of Bacterial Spores and Vegetative Bacterial Cells by Interaction with ZnO-Fe₂O₃ Nanoparticles and UV Radiation

ZnO-Fe₂O₃nanoparticles (ZnO-Fe NPs) were synthesized and characterized by scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDS) and dynamic light scattering (DLS). The generation of chemical reactive hydroxyl radicals (^•OH) was measured spectrophotometrically (UV-Vis) by monitoring of <em>p</em>-nitrosodimethylaniline (<em>p</em>NDA) bleaching. Inactivation of <em>E. coli</em> and <em>B. subtilis</em> spores in the presence of different concentrations of ZnO-Fe NPs, under UV_365nm or visible radiation, was evaluated. We observed the best results under visible light, of which inactivation of <em>E. coli</em> of about 90% was accomplished in 30 minutes, while <em>B. subtilis </em>inactivation close to 90% was achieved in 120 minutes. These results indicate that the prepared photocatalytic systems are promising for improving water quality by reducing the viability of water-borne microorganisms, including bacterial spores