The Preparation, Characterization And Application Of Doped TiO₂ Photocatalyst

To improve photocatalytic ability of TiO₂ catalyst, N or Fe ions were involved in the crystal of TiO₂ via sol-gel method used urea or Fe(NO₃)₃·9H₂O as the doping which brought the visible-light sensitization of TiO₂ catalyst, and studied the different effect mechanism of nonmetal and metal doping. To evaluate the research of industrialisation application, the photooxidation of industrial waste was carried out in a series of experiments. The primary study was listed as following:(1) Calcined at 400℃in air atmosphere, as-prepared N/TiO₂ catalysts are entirely anatase phase. The surface of as-prepared N/TiO₂ catalyst is 109.1 m²Â·g^-1. average pore size is 69.9 nm, and the grain pathway is about 17.7 nm. Better surface structural improve the adsorption power of the pollutants, and the catalysts show high photocatalytic activity. The optimum N-content in N/TiO₂ is dertermined as 2.98 at.%. Moreover, the light absorption of as-prepared N/TiO₂ shows red-shift to 435 nm, the band gaps is determined to be 2.85 eV. The nitrogen atom enters into the TiO₂ lattice, occupies the position of oxygen atom, forms the bond of N-Ti-O, narrows the band gaps and makes as prepared N/TiO₂ shifted into the visible ragion.(2) In as-prepared Fe/TiO₂ catalysts, the optimum Fe-content is dertermined as 0.64 at.%. The Fe-doping not only depresses the grain growth of TiO₂ particles, but also reduces the phase transformation temperature of anatase to rutile. Calcined at 300℃in air atmosphere, as-prepared Fe/TiO₂ catalysts are anatase phase, the grain pathway is about 8 nm. The surface of as-prepared Fe/TiO₂ catalysts is 91.3 m²Â·g^-1, average pore size is 57.9 nm. The existence of Fe changes the surface structure of catalysts, which consequently reduces the chance of the recombination of the photoinduced electrons and holes. Calcined in air atmosphere at the temperature of 400℃, the light absorption of as-prepared Fe/TiO₂ shows red-shift to 459 nm, the band gaps reduces to 2.7 eV. The promoting effect of Fe-doping on the photocatalytic activity could be attributed to the formation of intermediate energy level that allows Fe/TiO₂ to be activated easily in the visible area.(3) In the multiphase photocatalysis reaction system, The application of photocatalysis is studied through the photodegradation of industrial waste diluted 1 times in oxygenated aqueous suspensions containing as-prepared TiO₂. The experiment result shows: after 180 minutes' photoreaction, the degradation rate of TOC is higher than 80%. The concentration of TOC falling demonstrated the organic pollutants in the industrial waste were photodegraded. The total carbon in the system falling is due to the final outcome CO₂ departing from the reaction system, but TN has no change, this indicated the N element of the organic pollutants were not photodegraded to be N₂. The 10% degradation rate of Pb²⁺ in the industrial waste is owing to the adsorption ability of the as-prepared photocatalyst.