Phosphate Modified Mesoporous Titania: Synthesis, Characterization And Application

Mesoporous titania are new mesoporous materials, attracting research interests due to the specific synthesis, extremely large surface area large, the surface modified easily and their high thermal stability. ordered mesoporous titania presents well-defined pores and flexible framework composition, which make it a promising candidate for catalysis, adsorption, hydrogen storage and electrochemistry etc. In this thesis, a series of ordered phosphate/phosphonate and nitrogen modified mesoporous titania materials were prepared based on the free template and mixed templates.Mesoporous titania materials have been synthesized through a facile template-free method using tetrabutyl titanate as titanium source in ethanol system, which were further modified by phosphate and nitrogen, in order to improve the photocatalytic properties. Both the synthesized phosphate modified titanium oxides and the N-doped sample are amorphous with mesopores. The formation of Ti–O–P bonds during the synthesis process was revealed by the FT-IR and XPS spectra. The compounds were used for the adsorption of proteins lysozyme from buffer solution in different pH environment. The amount adsorbed depends on the pH of solution as well as on the pore volume and the composition of the adsorbent. The maximum adsorption was achieved at the isoelectric point with q_e=32.68μmol/g. The mesoporous phosphate and nitrogen doped titania materials exhibit high photocatalytic activity in photodegradation of Rhodamine B under UV and visible light irradiation. Degradation rate can reach 72% and 42% under UV and visible light respectively.Macro-mesoporous titania phosphates were synthesized with the mixed template cetyltrimethylammonium bromide (CTAB) and Octyl polyethylene glycol phenyl ether (OP-10). The prepared sample was characterized by XRD, N₂ adsorption-desorption, FT-IR. The macro-mesoporous structure was formed in water/ethanol system with surface area of 162m²/g and macropores of 1～2μm. The mesoporous structure was formed in ethanol sysytem and surface area was 272m²/g with total pore volume of 0.359 cm³/g and pore size of 3.7 nm. The material was used as adsorbent for the adsorption of lysozyme in different pH solution. The maximum adsorption was achieved at the isoelectric point with q_e=25.94μmol/g. The isotherms for the lysozyme adsorption are of type L (Langmuir isotherm). The synthesized sample was confirmed to be a kind of adsorbent for the lysozyme.Mesoporous titania materials were modified by organic phosphonate ethylene diamine tetra (methylene phosphonic acid) and diethylene triamine penta (methylenephosphonic acid) in the absence of template agents. Meanwhile, inorganic phosphate modified TiO₂ was prepared and mesoporous TiO2 was also synthesized denoted as TiO2 for comparison. The obtained samples were characterized by XRD, N₂ adsorption-desorption, UV-Vis, FT-IR. These mesoporous titania–phosphonate materials exhibited high photocatalytic activity in photodecomposition of Rhodamine B dye molecules whether under UV or visible-light irradiation and photoreduction of Cr(VI) under UV-light irradiation. Rhodamine B degradation rate can reach 72% and 42% under UV and visible light respectively. While, degradation rate of Cr⁶⁺ (10mg/L) can reach 44%. The results suggested that the synthesized mesoporous titanium phosphonate was the useful photocatalyst.