Modified nanostructured titania photocatalysts for aquatic disinfection applications

According to the SDG 6, everyone on earth should have access to safe and affordable drinking water. In sharing water-treatment technologies that leads to accomplishing this goal, it is imperative to devise ways of removing microbial contaminants such as E. coli from drinking water especially in resource-limited settings that lack centralized water supply systems. One of the approaches is bacterial disinfection of water at the point of use. In this study, the bactericidal effects of the photocatalysis of titanium dioxide-based nanoparticles under UV and visible light are explored. Pristine and silver doped nanostructured mesoporous titanium dioxide (Ag-TiO₂, TiO₂) particles with high specific surface area and average crystallite domain size of ~ 7.0-7.5 nm were prepared using the simple and cost effective sol-gel technique followed by thermal treatment. The addition of Ag⁺ ions during the hydrolysis/condensation of the Ti^(IV) molecular precursor led to homogeneous dispersion of the Ag⁺ cations on the titania matrix. The As-prepared nanoparticles were characterized using X-Ray Diffraction (XRD), Brunauer-Emmett-Teller (BET) surface area analysis, Transmission Electron Microscopy (TEM), Scanning Electron Microscopy (SEM), thermogravimetry, Fourier Transform Infra-Red (FTIR), and Raman Spectroscopy. X-ray diffraction, FTIR and Raman spectroscopy confirmed that the crystalline structure of the TiO₂ matrix corresponds to the anatase polymorph; however, the presence of the dopant led to an increase in the system disorder due to the rise in concentration of oxygen vacancies. The As-prepared nanoparticles were used for Escherichia coli (E. coli) inactivation under dark and UV-Visible light conditions. Under dark conditions, Ag doped titania and pristine titania resulted in ~ 95% and ~ 64% E. coli population inactivity while under light conditions, ~99% and ~97% degradation respectively were observed. Taken together, these results demonstrate that, the synthesized TiO₂ nanoparticles have promising applications in the light mediated point of use inactivation of bacterial contaminants in water.