Papers by Keyword: Titania (TiO2)

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Authors: Ree Ho Kim, Sang Ho Lee, Jung Hun Lee, Young Min Kim
Abstract: Rainwater utilization has great potentials for recovering hydrological cycles, for buffering extreme run-off situations in the watercourses, and for reducing the costs for water supply in urban area. However, little information is available on the water qualities and runoff properties of collected rainwater, which is critical for efficient design and maintenance strategies of rainwater harvesting facilities. In this study, characteristics of rainwater collected in a rainwater harvesting system were examined in terms of pollutant concentrations. Based on these results, TiO2 photocatalysts were applied on the roof surface as a novel coating material to improve the quality of collected rainwater. The analysis of rainwater samples shows that the contamination by turbidity, conductivity, and color occurs during the catchment process, which may result in troubles for further use. The roof coating technique developed in this study appeared to be effective in increasing the wash-off of pollutants and improving the water quality in roof runoff because of its increased hydrophililicy as well as photocatalytic reactivity. Further research is required on trace pollutants such as endocrine disruptors to estimate and minimize health risk in rainwater harvesting.
Authors: Xin Ping Lin, Fu Qiang Huang, Wen Deng Wang, Zhi Chao Shan, Jian Lin Shi
Abstract: A series of layered-structure Bi-based oxychlorides such as BiOCl, Bi3O4Cl, Na0.5Bi1.5O2Cl, Bi4NbO8Cl and MBiO2Cl (M = Ca, Sr, Ba, Cd, Pb) used as efficient photocatalysts. Among them, Bi3O4Cl (Eg = 2.79 eV), Na0.5Bi1.5O2Cl (Eg = 3.03 eV), Bi4NbO8Cl (Eg = 2.38 eV) and PbBiO2Cl (Eg = 2.45 eV) are visible-light-responsive. The powders synthesized by solid state reactions were characterized by X-ray diffraction (XRD) and UV-Vis diffuse reflection spectrum. Their photocatalytic activities were evaluated by the degradation of methyl orange. The results generally show that the UV-induced photocatalytic performances of the novel oxychloride catalysts are better than or comparable to that of anatase TiO2. The high photocatalytic performance of Bi-based oxychlorides is mainly ascribed to the presence of strong internal static electric fields between layers.
Authors: Ching Song Jwo, Chien Chih Chen, Ho Chang, Sih Li Chen, Chi Hsiang Lin
Abstract: This research carries out an inexpensive, rapid and novel exercise, which is applied to perform the photocatalyst decomposition effectiveness of Methanol and Ethanol in gaseous form. The major devices of this applicable measurement developed by this practice are only utilizing ultraviolet-visible spectrophotometer and quartz cuvette, and the experimental procedures are straightforward and speedy. In the conduct experiments, Methanol and Ethanol with a specific concentration is initially injected into an enclosed quartz cuvette. Then the cuvette is put in ultraviolet- visible spectrophotometer to measure the Methanol and Ethanol concentration, so as to obtain an unique UV absorbance spectrum at its particular concentration. In the conduct experiments of measuring photocatalyst decomposition efficiency, the self-made (SANSS) nanocatalyst TiO2 is initially coated in the quartz plate, and put into the quartz. Then a specific concentration of methanol alcohol and ethanol is injected into the quartz cuvette under the UV irradiation exposure, so as to carry out photodecomposition of Methanol and Ethanol experiment. After that, the cuvettes are then put into the ultraviolet-visible spectrophotometer for measuring the absorbance intensity of UV spectrums in order to produce degradation chart. The preliminary results point out that the self-made nanocatalyst TiO2 has exceptionally outstanding decomposition efficiency which further points out the fact that, when UV irradiation for 60minutes, the gaseous Methanol can be reduced to 3.8% of the original sample, and the gaseous Ethanol can be reduced to 6% of the original sample. But when exercising with commercial nanocatalyst TiO2 to undergo the same process exactly under the same circumstances, the residue gaseous concentration can only be reduced to 17% and 16% of the gaseous Methanol and Ethanol original sample.
Authors: Angela Hardmann, F.H. Hayes
Authors: Guan Qin Chen, Zhang Lian Hong
Abstract: Low frequency ultrasonic treatment was applied to desorb surface organics from the surface of nanosized TiO2 photocatalyst, which was prepared by hydrothermal method using a mixture of different amounts of Ti(OBu)4, ethanol, acetone and pyridine raw materials. The UV-Vis, TG-DTA and GC-MS analysis were used to investigate the surface organics. It was found that the absorption intensity around 250nm in UV-Vis spectra of the upper transparent solution, which represents the amount of organics desorbed from the TiO2 surface, increased with increasing treatment time. Along with the TG-DTA and GC-MS analysis, the kinds and amounts of partial surface organics were roughly clarified, and these organics may correspond with the photocatalytic degradation rate for methyl orange (MO) solution under visible light irradiation (≥450nm).
Authors: Juan Liao, An Chun Mo, Hong Kun Wu, Jing Chao Zhang, Yu Bao Li, Guo Yu Lv
Abstract: Since bacterial accumulation surrounding biomaterials has pathogens known to cause the biomaterials centered infection, it may be important to develop some kind of biomaterial with antibacterial activity as well as biocompatibility. This study focused on evaluating the antibacterial activity of silver-hydroxyapatite/ Titania nanoparticles (Ag-nHA/nTiO2) against oral bacteria with agar dilution method. Bacteria were seeded on agar plate containing antibacterial material with different concentrations after incubation of 48 hours. The antibacterial activity was demonstrated by MICs. The MICs of Ag-nHA/nTiO2 ranged between 1000μg/ ml and 7500μg /ml under anaerobic conditions. And it also exhibited remarkable antibacterial activity to all the aerobe bacteria (MIC≤500μg/ml). On the other hand, the antibacterial activities of Ag-nHA/nTiO2 differentiate to some extent with the bacterial strains. This Ag-nHA/nTiO2 exhibited remarkable antibacterial activity to anaerobic and aerobe bacteria. This antibacterial effect may reduce the potential for bacterial colonisation of oral biomaterials with Ag-nHA/nTiO2.
Authors: Tie Zhang, Dong Bin Zhu, Chun Guang Wang, Xin He
Abstract: An Ag-Ce-TiO2 composite film was prepared by incorporating Ag in the Ce-TiO2 films with an impregnation method through photoreduction. The bactericidal activity of the Ag-Ce-TiO2 composite film and the effect of deposition of silver and doping cerium in the different irradiations on the antibacterial performance were assessed against Escherichia coli (E. coli). TIhrough characterization of X-ray diffraction (XRD), X-ray photoelectronic spectra (XPS) and UV/VIS diffusive reflectance spectra (DRS), it was found that the Ag-Ce-TiO2 composite film was composed of predominant anatase titania, cerium oxides (in the form of Ce2O3/CeO2) and silver nanoparticles. Moreover, the bactericidal activity of the Ag-Ce-TiO2 composite film and the effect of deposition of silver and doping cerium in the different irradiations on the antibacterial performance were assessed against Escherichia coli (E. coli). The results show that the Ag-Ce-TiO2 composite film has much higher antibacterial efficiency than that of glass and pure TiO2 film either in the room light or in the dark. Therefore, this composite film is promising in applications of antimicrobial and self-clean technologies.
Authors: Hidekazu Tanaka, Ikuyo Higashio, Keiichi Watanabe, Yoko Suyama
Abstract: Fibrous TiO2 with ca. 0.16 mm in width and 5 - 6 cm in length was prepared by drying a suspension of monodispersed anatase particles at 363 K in air. The TiO2 fibers thus obtained were thermally treated at the temperatures ranging from 363 to 1273 K for 1 h in air. Elevating the treating temperature increases the crystallinity of anatase phase and reduces the specific surface area from 98 to 5 m2/g due to the sintering of particles. The rutile phase appears at 1273 K by transformation of anatase phase. A photocatalytic activity of the fibers was examined by decomposition of methylene blue (MB) in water under UV irradiation centered at 365 nm. The fibers decomposed the MB in aqueous media under UV irradiation, indicating that the fibers possess a high photocatalytic activity. The catalytic activity is considered to be enhanced on increasing the crystallinity of anatase phase, nevertheless, that decreased with generation of rutile phase.
Authors: Jong Oh Kim, Jong Tae Jung, Won Youl Choi
Abstract: This study was conducted to evaluate the applicability of photocatalytic metal membrane system for the treatment of humic acid and heavy metals in aqueous solution. The catalysts, TiO2 powder P25 Degussa and metal membrane with 0.5 μm nominal pore size were used for experiments. Removal efficiency of humic acid and heavy metals increased with the increase of TiO2 dosage, however decreased over 0.3 g/L of TiO2 dosage. The addition of H2O2 as an oxidation reagent had a positive effect for the removal rate of humic acid and heavy metals. Metal membrane with stainless steel seemed to be quite stable to UV light with oxidation reagent in long-term operational periods over 6 months. Moreover, TiO2 particles can be effectively separated from the treated water by membrane rejection and the permeation flux was also enhanced by the combination of photocatalytic reaction.
Authors: A.P.P. Fontanesi, J.M. Cavenaghi, Vania Caldas de Sousa
Abstract: Dopants such as Ta2O5 play a major role in the formation of barriers at the grain boundary in TiO2 varistors, increasing their nonlinear coefficient and decreasing their breakdown electric field. This paper discusses the microstructural and physical properties of Ta- and Cr-doped TiO2 systems in which imported tantalum oxide was replaced with an equivalent Brazilian raw material. Preliminary results confirm that this national oxide can be utilized to obtain electroceramics such as varistors.
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