Příprava a charakterizace oxidů kovů na bázi Ti, La a N pomocí přetlakových a superkritických tekutin využitelných pro snižování znečištění životního prostředí

Abstract

This diploma thesis is focused on preparation of nanostructured oxide based on Ti, La and N by using pressurized hot water and pressurized hot/supercritical methanol, its physico-chemical characterization and investigation of its photocatalytic activity in photodegradation of model azo-dye Acid orange 7 under UV light. The goal of this work was the revelation of optimal nitrogen amount doped to La/TiO2 and optimization of processing conditions (water volume, temperature and pressure) in the way to prepare the most active N-La/TiO2 photocatalyst in photodegradation of azo-dye Acid orange 7. Nanostructured N-La/TiO2 powder photocatalyst was prepared by processingof gel precursor synthesized via sol-gel method, controlled in the reverse micellar environment of non-ionic surfactant Triton X-114, by pressurized hot water and pressurized hot or supercritical methanol. The influence of nitrogen doping (10-50 hm.%), water volume used for crystallization (1-2 l), temperature (25 250 °C) and pressure (10-30 MPa) on the purity, textural, structural, optical and photocatalytic properties of N-La/TiO2 was investigated. The purity of N-La/TiO2 was characterized by using organic elementary analysis, textural properties such as the specific surface area and pore-size distribution were determined by using nitrogen physisorption, structural properties by X-ray diffraction and optical properties by diffuse reflectance measurements in UV-Vis region. Photodegradation effect was evaluated by using UV-Vis spectrophotometry. It was found out that the doped amount of nitrogen and temperature affect significantly the texture, structure and crystallite-size of anatase in N-La/TiO2. Moreover, processing temperature affects significantly the purity and optical properties of N-La/TiO2 as well. Volume of water and pressure influence the structure of anatase in N-La/TiO2. 10 hm.% N La/TiO2 processed at 225 °C, 10 MPa, using the sequence of 1,5 l of water, 0,25 l of methanol a 0,1 l of water showed the highest photocatalytic activity in photodegradation of Acid orange 7.Using optimal processing conditions the reference TiO2, 10 hm.% N/TiO2 and 0,2 hm.% La/TiO2 photocatalysts were prepared. TiO2 dopation by nitrogen and lanthanum influence the anatase crystallite-size. Moreover, lanthanum in TiO2 influences the anatase structure. Based on the comparison of photocatalytic activity of developed photocatalysts it may be stated that 10 hm.% N-La/TiO2 shows higher photocatalytic activity than all reference photocatalysts.