Photocatalytic Disinfection of Selected Waterborne Pathogens by Visible Light-Active Nano Iron-Doped TiO₂ Obtained by a Sol–Gel Method

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-TiO₂) for the photocatalytic disinfection of Gram-negative <i><i>E. coli</i></i> and Gram-positive <i>S. aureus</i> under visible light. The Fe-TiO₂ 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 m²/g. A sample of undoped anatase TiO_2, obtained using the same sol-gel method and exhibiting a specific surface area of 116 m²/g, was utilized to confirm the role of Fe-doping in disinfection. The nanopowders were characterized using X-ray diffraction, N₂ 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-TiO₂ 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-TiO₂, a 99.9% removal of both <i><i>E. coli</i></i> and <i>S. aureus</i> was achieved starting from a bacterial concentration of 1 × 10⁶ CFU/mL. A 99.9% removal of <i><i>E. coli</i></i> and a 99.8% removal of <i>S. aureus</i> were achieved starting from 1 × 10⁴ CFU/mL. The Fe-TiO₂ nanomaterial was effective against high concentrations of both bacteria under visible light. Reusability was studied by recovering the Fe-TiO₂ nanoparticles and assessing their performance over three cycles. The photocatalytic disinfection effectiveness of Fe-TiO₂ nanoparticles under visible light was validated using an actual tap water sample containing 167 CFU/mL <i>total coliforms</i> and 8 CFU/mL <i><i>E. coli</i></i> . The bacteria were photocatalytically inactivated within 30 min.