Preparation And Visible Light Photocatalytic Performance Of Iodine-doped And Iodine-Nitrogen-codoped TiO₂

Visible-light-driven photocatalytic technology has attracted much attention because it is a vital step in using solar energy. TiO₂ is considered the most promising application as photocatalyst because of its chemical stability, excellent functionality, nontoxicity, relatively low price and non-secondary pollution. Normally, TiO₂ can be activated only in the UV region (<400nm), about 4% of the incoming solar energy, because of its large band gap of about 3.2 eV, any shift in the optical response of TiO₂ to the visible spectral range will have a profound positive effect on the photocatalytic efficiency . In recent years, the visible light photocatalytic oxidation technique of TiO₂ has become the highlight in the environmental protection.The content of this thesis is divided into two parts. Firstly, Iodine-doped TiO₂ nanoparticles were synthesized by sol-gel method. The prepared samples were characterized by XRD, UV-visible reflectance spectroscopy, Raman, BET, TG-DTA, XPS and electrochemistry analyses. The photocatalytic activities were evaluated by the photodegradation of methyl orange under visible irradiation. The iodine-doped TiO₂ samples showed higher photocatalytic activity than the pure TiO₂. By investigation the crystal structures, optical properties, surface structure and photocatalytic activity of various samples, we presume the oxygen vacancies and large effective surface area contributed to the visible light activity.In second part, a series of iodine-nitrogen-codoped TiO₂ photocatalysis were prepared by direct hydrolysis of tetrabutyl titanate through iodine-doping and calcined with urea. XRD, Raman, IR spectra, XPS, UV-visible reflectance spectroscopy and electrochemistry analyses were performed to characterize the behavior of these catalysts, such as optical property, dimension and structure. The effects of different iodine content, reaction time on the photocatalysis degeneration of Azithromycin (one of the macrolide antibacterial agent) Pharmaceutical Wastewater were discussed respectively. These codoped-TiO₂ photocatalysis show stronger absorption in visible light range with a red shift in the band gap transition and higher photocatalytic activity than pure nitrogen-doped TiO₂ and iodine-doped TiO₂. When the system used ENT350 as photocatalyst, the highest COD removal rate is 57% under visible light 12 hours. The high activity was ascribed to a synergetic consequence of several beneficial effects induced by the I-N-codoping, N atomes replace the oxygen lattice, surface hydroxy, oxygen vacancies and co-phase effect.