Synthesis design of TiO₂ nanotubes and nanowires and photocatalytic applications in the degradation of organic pollutants in the presence or not of microorganisms

1 D TiO₂ nanomaterials (nanotubes, nanowires) were synthesized through hydrothermal treatment of TiO₂ powder (P25) in concentrated alkaline solutions (NaOH for nanotubes, KOH for nanowires) followed by calcination at varying temperatures between 400°C and 700°C Samples were characterized by HRTEM, XRD, Raman spectroscopy, and N₂ adsorption-desorption isotherms. High surface area nanotubular TiO₂ materials can maintain their 1D morphology up to a temperature of calcination of 400°C while changing their phase from hydrogenotitanate to anatase. The use of KOH leads to a retarded formation of anatase. Photocatalytic results showed that TiO₂ anatase nanotubes calcined at 400°C can degrade formic acid with a rate constant four times higher than for P25. A direct correlation between surface area and photocatalytic activity explains the much higher activity of TiO₂ anatase nanotubes. On the opposite, for the degradation of phenol, P25 remains more active. In the disinfection of water, contrary to P25, the high surface area of TiO₂ nanotubes allows the simultaneous degradation of formic acid and the inactivation of pathogen fungus showing the interest of such materials for the treatment of wastewater.