Titanium dioxide-based nanomaterials for photocatalytic water treatment

Water treatment using photocatalysis has gained extensive attention in recent years. Photocatalysis is promising technology from green chemistry point of view. The most widely studied and used photocatalyst for decomposition of pollutants in water under ultraviolet (UV) irradiation is TiO₂ because it is not toxic, relatively cheap, and highly active in various reactions.Within this thesis, unmodified and modified TiO₂ materials (powders and thin films) were prepared. Physicochemical properties of photocatalytic materials were characterized with UV-visible spectroscopy, scanning electron microscopy, transmission electron microscopy, X-ray photoelectron spectroscopy, inductively coupled plasma optical emission spectroscopy, ellipsometry, time-of-flight secondary ion mass spectrometry, Raman spectroscopy, goniometry, diffuse reflectance measurements, thermogravimetric analysis, and nitrogen adsorption/desorption. Photocatalytic activity of prepared samples in aqueous environment was tested using model compounds such as phenol, formic acid, and metazachlor. In addition, purification of real pulp and paper wastewater effluent was studied. Concentration of chosen pollutants was measured with high-performance liquid chromatography. Mineralization and oxidation of organic contaminants were monitored with total organic carbon (TOC) and chemical oxygen demand (COD) analysis. Titanium dioxide powders prepared via sol-gel method and doped with dysprosium and praseodymium were photocatalytically active for decomposition of metazachlor. The highest degradation rate of metazachlor was observed when Pr-TiO₂ treated at 450°C (8h) was used. The photocatalytic light-emitting diode-based treatment of wastewater effluent from plywood mill using commercially available TiO₂ was demonstrated to be promising posttreatment method (72% of COD and 60% of TOC was decreased after 60min of irradiation). The TiO₂ coatings prepared by atomic layer deposition technique on aluminum foam were photocatalytically active for degradation of formic and phenol; however, suppression of activity was observed. Photocatalytic activity of TiO₂/SiO₂ films doped with gold bipyramid-like nanoparticles was about two times higher than reference, which was not the case when gold nanospheres were used.