Development of TiO₂ Films by Sol–Gel/Sedimentation for the Inactivation of Multidrug-Resistant Escherichia coli and Salmonella Typhimurium in Greywater

Crystalline TiO₂ films were synthesized on hydrophilic glass substrates by Peroxo sol–gel and sedimentation (S1–S4) and compared with conventional sol–gel protocols (S5–S10). The films were deposited on soda-lime glass and characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDS), and UV–Vis absorption. Photocatalytic activity was evaluated through the inactivation of multidrug-resistant Escherichia coli and Salmonella Typhimurium, and the removal of chemical oxygen demand (COD) from greywater under UV irradiation. The obtained films exhibited anatase crystallinity, crystallite sizes of ~60 nm, and grain sizes between 1.5 and 3.0 µm. S1 films showed a bandgap of 3.26 eV (380 nm). Under UV exposure, S1 reduced E. coli and S. Typhimurium by 4.78 and 3.00 Log₁₀ units, respectively, at pH 5.0 after 30 min, while COD decreased to 380 mg L⁻¹ compared to 433 mg L⁻¹ with UV photolysis alone. Increasing TiO₂ loading and extending irradiation to 120 min further enhanced bacterial inactivation (93 and 78% for E. coli and S. Typhimurium), COD (33%), NH₄⁺ (90%), and H₂S (89%) oxidation, outperforming UV-light controls. These results indicate that S1 films exhibited superior crystallinity, photocatalytic performance, and bacterial inactivation compared to other protocols, although complete mineralization was not achieved.