Photocatalytic Disinfection of Selected Waterborne Pathogens by Visible Light-Active Nano Iron-Doped TiO<sub>2</sub> Obtained by a Sol–Gel Method
Najeebullah Channa, Tanveer A. Gadhi, Francesca S. Freyria, Alessandro Chiadò, Nicola Blangetti, Nicoletta Ditaranto, Barbara Bonelli
Abstract
High Resolution Image Download MS PowerPoint Slide Bacterial contamination in drinking water systems poses a serious health risk due to poor hygiene, human activities, and cross-contamination within the water supply. This study examines the potential of iron-doped titanium oxide nanometric powder (Fe-TiO 2 ) for the photocatalytic disinfection of Gram-negative E. coli and Gram-positive S. aureus under visible light. The Fe-TiO 2 photocatalyst, with an optimal nominal content of 2.5 wt % Fe, was synthesized using a surfactant-assisted sol–gel method, resulting in a mesoporous nanomaterial composed of anatase nanoparticles with a specific surface area of 123 m 2 /g. A sample of undoped anatase TiO 2, obtained using the same sol–gel method and exhibiting a specific surface area of 116 m 2 /g, was utilized to confirm the role of Fe-doping in disinfection. The nanopowders were characterized using X-ray diffraction, N 2 sorption at −196 °C, diffuse reflectance UV–vis spectroscopy, X-ray photoelectron spectroscopy, electrophoretic mobility measurements, high-resolution transmission electron microscopy combined with energy-dispersive X-ray spectroscopy, and field emission scanning electron microscopy. Photocatalytic disinfection tests were conducted using 1 and 0.5 g/L Fe-TiO 2 with varying initial bacterial concentrations, with 1 g/L yielding the most promising results under the experimental conditions employed. After 240 min of treatment with 1 g/L Fe-TiO 2, a 99.9% removal of both E. coli and S. aureus was achieved starting from a bacterial concentration of 1 × 10 6 CFU/mL. A 99.9% removal of E. coli and a 99.8% removal of S. aureus were achieved starting from 1 × 10 4 CFU/mL. The Fe-TiO 2 nanomaterial was effective against high concentrations of both bacteria under visible light. Reusability was studied by recovering the Fe-TiO 2 nanoparticles and assessing their performance over three cycles. The photocatalytic disinfection effectiveness of Fe-TiO 2 nanoparticles under visible light was validated using an actual tap water sample containing 167 CFU/mL total coliforms and 8 CFU/mL E. coli . The bacteria were photocatalytically inactivated within 30 min.