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 E. coli and Gram-positive S. aureus 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 E. coli and S. aureus was achieved starting from a bacterial concentration of 1 × 10⁶ CFU/mL. A 99.9% removal of E. coli and a 99.8% removal of S. aureus 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 total coliforms and 8 CFU/mL E. coli. The bacteria were photocatalytically inactivated within 30 min.