Anatase TiO2 has attracted a lot of attention due to its applications as a photocatalyst in water and air treatment technologies. However, its large band gap energy (⁓3.2 eV) limits its application only to UV light. Also, anatase TiO2 suffers from high electron/hole recombination, which diminishes its photocatalytic activity. Therefore, different methods have been employed to decrease its band gap energy and reduce the recombination of the charge carriers. One of the methods is to incorporate impurities as dopants in its crystal lattice. Different metal and non-metal dopants have been studied for this aim. Among the different choices, Fe3+ has showed a great potential to improve the photocatalytic activity of TiO2 under visible light irradiation. Firstly, the d orbitals of Fe3+ interact with the 3d orbitals of Ti4+ generating intermediate band gap energy levels to facilitate excitation of electrons under visible light by a red shift in the absorption of light. Secondly, Fe3+ can interact with both electrons and holes to produce Fe2+ and Fe4+ trapping the charge carriers and reducing their recombination rate. Fe2+ and Fe4+ can release the electron and hole and revert back to the Fe3+. The released charge carriers migrate to the surface of the nanoparticles to initiate the photocatalytic reactions. However, it was found that the photocatalytic activity of Fe-TiO2 is not as high as expected. Therefore, in this research study I investigated the cause for its low photocatalytic activity and found methods to improve it. The Fe-TiO2 was synthesized using a facile sol-gel method and its structure and properties were characterized by different instrumental techniques. Using TEM and HRTEM an amorphous layer was seen on the surface of the nanoparticles. This layer characterized using XPS and EDX was composed of iron oxide layers. This layer was contaminating the surface of the nanoparticles where the photocatalytic reactions take place. Moreover, the contamination layer was acting as a recombination center for the electrons and holes. To the best of our knowledge, no previous study was conducted to investigate the effect of an iron oxide contamination layer on the photocatalytic activity of Fe-TiO2 nanoparticles. This layer was removed using a concentrated HCl solution confirmed using HRTEM and XPS. Also, using DRS it was shown that its removal does not effect the optical properties of the Fe-TiO2 confirming that the acid treatment process did not influence the doped Fe3+ in the TiO2 crystal lattice. The degradation of methelyne orange (MO), a representative pollutant, was increased from 25% to 98% under visible light irradiation. Also, in order to achieve the highest performance of the photocatalyst, it was necessary to study the parameters of the photocatalytic activity and the degradation efficiency. Therefore, experiments using a phenol solution, another representative pollutant, were conducted to investigate and optimize the effects of the catalyst load, reaction time, initial concentrating of the pollutant and pH. The degradation efficiency of the phenol solution was found to increase from 31% to 57% by the removal of the contamination layer and by controlling the pH of the solution. / Graduate

>Magister Scientiae - MSc / The heterogeneous photocatalytic oxidation of dinitrogen to nitrate, NO3 and/or nitrite, no2 using peroxy species of titanium (IV) in aqueous suspensions has been investigated. The photocatalysts used were titanium peroxide and Degussa p25 TiO2 pretreated with H2O2. These photocatalysts were investigated by SEM and FTIR spectroscopy.

A aplicação de semicondutores no tratamento de água e efluentes líquidos é uma tecnologia de remediação ambiental promissora, em especial para poluentes orgânicos. Entre os vários semicondutores que também são fotocatalisadores, o TiO2 é amplamente usado em aplicações ambientais, por ser inerte biológica e quimicamente, ter elevado potencial de oxidação, baixo custo e estabilidade frente à corrosão. Entretanto, o TiO2 também tem algumas desvantagens, tais como: ele é excitado apenas por luz UV e requer uma operação unitária adicional (por exemplo, filtração ou centrifugação) para o reuso do catalisador. Para contornar estas limitações, usou-se um procedimento simples para a síntese de um fotocatalisador magnético (Fe3O4/TiO2) com alta área superficial específica e atividade catalítica, quando comparado com o TiO2 P25 da Evonik. O fotocatalisador foi sintetizado através de um procedimento em três etapas: (1) Partículas α-Fe2O3 foram obtidas por precipitação de uma solução de FeCl3.6H2O 0.01 mol L-1, que foi submetida a uma hidrólise forçada à 100°C por 48 h; (2) Partículas de α-Fe2O3/TiO2 foram obtidas por heterocoagulação de oxi-hidróxidos de Ti(IV) sobre as partículas de α-Fe2O3, as quais foram calcinada a 500°C por 2 h; e (3) As partículas \"casaca/caroço\" do fotocatalisador foram obtidas por calcinação a 400°C por 1 h sob atmosfera redutora (H2). A atividade fotocatalítica do material sintetizado foi avaliada aplicando-o no descoramento de uma solução do corante Azul Ácido 9 (C.I. 42090). Os efeitos do pH e da concentração de catalisador foram estimados por meio de um planejamento fatorial 22. Foi obtido um fotocatalisador com área superficial específica de 202 m2 g-1, facilmente separável do meio reacional em aproximadamente 2 min com o auxílio de um ímã. O fotocatalisador apresentou absorção em toda a região do visível. A maior remoção de cor (54%) foi obtida com pH 3,0, 1,0 g L-1 de catalisador e 2 horas de reação. / The use of semiconductors for treating polluted waters and wastewaters is a promising environmental remediation technology, especially for organic pollutants. Among the several semiconductors that are also photocatalysts, TiO2 is extensively used for environmental application, due to its biological and chemical inertness, high oxidation power, low cost, and stability regarding corrosion. However, TiO2 also has some disadvantages, such as: it is only UV-excited and requires an additional unit operation (e.g. filtration or centrifugation) for reuse purposes. In order to work around those limitations, a simple procedure for synthesizing a magnetic photocatalyst (Fe3O4/TiO2), with high specific surface area and good photocatalytic activity when compared to Evonik\'s TiO2 P25, was used. The photocatalyst was synthesized in a three-step procedure: (1) α-Fe2O3 particles were obtained, by precipitation, from FeCl3.6H2O 0.01 mol L-1, which underwent a forced acid hydrolysis at 100°C for 48 h; (2) α-Fe2O3/TiO2 particles were obtained, by heterocoagulation, of Ti(IV) oxide species on the α-Fe2O3, followed by calcination at 500°C for 2 h; and (3) The core/shell photocatalyst particles were obtained by calcination the α-Fe2O3/TiO2 particles at 400°C for 1 h under reducing atmosphere (H2). The photocatalytic activity of the synthesized material was assessed by the color removal of an Acid Blue 9 (C.I. 42090) dye solution. pH and catalyst dosage effects were estimated by a 22 factorial design. Fe3O4/TiO2 core/shell particles with specific surface area of 202 m2 g-1were obtained. They were easily separated from the reaction medium, in approximately 2 min, with the aid of a magnet. The photocatalyst absorbed radiation throughout the visible spectrum. The greatest color removal (54%) was achieved with pH 3.0, 1.0 g L-1 of photocatalyst, and 2 h of reaction.

京都大学 / 新制・課程博士 / 博士(工学) / 甲第23389号 / 工博第4881号 / 新制||工||1763(附属図書館) / 京都大学大学院工学研究科分子工学専攻 / (主査)教授 田中 庸裕, 教授 今堀 博, 教授 佐藤 徹 / 学位規則第4条第1項該当 / Doctor of Philosophy (Engineering) / Kyoto University / DFAM

京都大学 / 0048 / 新制・課程博士 / 博士(工学) / 甲第22845号 / 工博第4785号 / 新制||工||1748(附属図書館) / 京都大学大学院工学研究科物質エネルギー化学専攻 / (主査)教授 陰山 洋, 教授 藤田 晃司, 教授 阿部 竜 / 学位規則第4条第1項該当 / Doctor of Philosophy (Engineering) / Kyoto University / DGAM

京都大学 / 0048 / 新制・課程博士 / 博士(工学) / 甲第19000号 / 工博第4042号 / 新制||工||1622(附属図書館) / 31951 / 京都大学大学院工学研究科分子工学専攻 / (主査)教授 田中 庸裕, 教授 今堀 博, 教授 阿部 竜 / 学位規則第4条第1項該当 / Doctor of Philosophy (Engineering) / Kyoto University / DFAM

京都大学 / 0048 / 新制・課程博士 / 博士(工学) / 甲第19235号 / 工博第4070号 / 新制||工||1628(附属図書館) / 32234 / 京都大学大学院工学研究科分子工学専攻 / (主査)教授 田中 庸裕, 教授 佐藤 啓文, 教授 阿部 竜 / 学位規則第4条第1項該当 / Doctor of Philosophy (Engineering) / Kyoto University / DFAM

京都大学 / 0048 / 新制・課程博士 / 博士(工学) / 甲第20385号 / 工博第4322号 / 新制||工||1670(附属図書館) / 京都大学大学院工学研究科材料化学専攻 / (主査)教授 三浦 清貴, 教授 田中 勝久, 教授 木村 俊作 / 学位規則第4条第1項該当 / Doctor of Philosophy (Engineering) / Kyoto University / DFAM

京都大学 / 0048 / 新制・課程博士 / 博士(人間・環境学) / 甲第20475号 / 人博第825号 / 新制||人||197(附属図書館) / 28||人博||825(吉田南総合図書館) / 京都大学大学院人間・環境学研究科相関環境学専攻 / (主査)教授 吉田 寿雄, 教授 内本 喜晴, 教授 田部 勢津久, 教授 加藤 立久 / 学位規則第4条第1項該当 / Doctor of Human and Environmental Studies / Kyoto University / DFAM

京都大学 / 0048 / 新制・課程博士 / 博士(工学) / 甲第21074号 / 工博第4438号 / 新制||工||1690(附属図書館) / 京都大学大学院工学研究科分子工学専攻 / (主査)教授 田中 庸裕, 教授 梶 弘典, 教授 今堀 博 / 学位規則第4条第1項該当 / Doctor of Philosophy (Engineering) / Kyoto University / DFAM