Des oxydes semi-conducteurs, en particulier TiO2 commercialement disponible ou des échantillons mésoporeux synthétisés, ont été testés comme photocatalyseurs de l'oxydation ménagée et aérobie d'alcools dans l'acétonitrile sous UV. L'alcool benzylique a été oxydé principalement en benzaldéhyde (rendement = 60%) en présence de TiO2-P25. Malheureusement, ce catalyseur tend à se désactiver. Le rôle du dioxygène dans le processus d'oxydation a été souligné après avoir testé différents solvants. Les alcools aliphatiques ont également été étudiés. Ainsi, le cyclohexanol a donné principalement de la cyclohexanone (rendement = 70%). Parallèlement, une approche colloïdale a été développée pour déposer les nanoparticules d'oxyde de titane sur des supports de silice mésoporeux SBA-15 transparents aux UV afin d'éviter les phénomènes d'agrégation lors des tests. Après optimisation de leur synthèse (quantité d'eau, nature de l'acide et de l'alcool), des nanoparticules sphériques non cristallines stables de 5 nm de diamètre ont été obtenues. En utilisant la méthode d'imprégnation à "deux solvants", ces dernières ont été introduites avec succès dans les mésopores de deux échantillons de SBA-15, l'un avec un diamètre moyen des pores de 6 nm, l'autre de 8. Les analyses MET ont souligné que le matériau SBA-15 avec les pores les plus grands a conduit à l'incorporation de davantage de nanoparticules. A priori, les interactions silice / oxyde de titane dans les matériaux résultants semblent favorables puisque les quantités inférieures de TiO2 dans les tests de photocatalyse correspondants ont conduit à de meilleurs taux de conversion que ceux obtenus avec P25 ou la suspension mère de colloïdes. / A series of metal oxides semiconductors, including commercially available TiO2 or synthesized mesoporous samples, were tested as photocatalysts for the aerobic mild oxidation of alcohols in acetonitrile under UV. Benzyl alcohol, used as a reference, was oxidized mainly into benzaldehyde. Best yield (60%) was obtained with TiO2-P25. Unfortunately, this catalyst tended deactivate with time. The role of dioxygen solubility in the oxidation process was emphasized through the test of different solvents. Aliphatic alcohols were also studied. Among them, cyclohexanol gave mainly cyclohexanone with a yield of 70%. Parallely, a colloidal approach was developed for the deposition of titanium oxide nanoparticles on UV transparent mesoporous silica supports in order to take advantage of their important specific surface area and avoid aggregation phenomena during the photocatalysis tests. After optimizing the synthesis protocol (amount of water, nature of the acid and alcohol), spherical, non-crystalline stable nanoparticles with 5 nm diameter were obtained. Using the “two-solvents” impregnation method, these particles were successfully introduced in the mesopores of two SBA-15 silica samples differing by their mean pore diameter (either 6 or 8 nm). TEM measurements emphasized that the SBA-15 material with the largest pores led to the incorporation of more nanoparticles in its mesopores. Clearly, silica/ titanium dioxide interactions in the resulting materials appeared to play a positive role since lower amounts of TiO2 in the corresponding photocatalysis tests led to improved conversion rates of benzylalcohol compared to those performed with P25 or the parent suspension of colloids.

Les matériaux à base de TiO2 ont déjà été très étudiés. En particulier, les films minces mésoporeux cristallins de TiO2 montrent une activité photo-catalytique élevée due à leur surface spécifique incomparable. Cependant, l'étude et l'optimisation de la photocatalyse dans un tel milieu poreux n'est pas si simple car le processus catalytique dépend de plusieurs paramètres environnementaux et structuraux. Les activités de recherche se sont essentiellement focalisées sur (i) la conception de couches mésoporeuses à base de TiO2 avec une composition et une nanostructure variée et (ii) leur mise en œuvre comme plateforme pour une étude fondamentale par ellipsométrie concernant le processus photocatalytique. Des films mésoporeux ont été produits en couplant la chimie sol-gel, et des procédés de dépôt. Parmi des outils de caractérisation analytiques, 2D-GISAXS, ellipsométrie, SEM-FEG, HR-TEM et WAXS sont notamment les techniques qui ont été utilisées pour obtenir des informations. Premièrement, un film mésoporeux de TiO2 a été analysé par ellipsométrie in-situ pour des investigations fondamentales sur les cinétiques de son processus photocatalytique dans l'air en fonction de la composition environnementale et du polluant organique. La grosse quantité d'information obtenue a d'ailleurs permis la proposition de mécanismes de photo-dégradation dans les conditions étudiées. Dans la seconde partie, des films minces mésoporeux mixtes TiO2/SiO2 avec des propriétés optiques ajustables ont été préparées. Une étude structurale a été conduite sur le réseau et la composition des films poreux. L'ellipsométrie a été également mis en œuvre pour étudier leur le activité photocatalytique. / TiO2-based materials have been extensively studied as potential material to be used in photocatalysis. In particular crystalline mesoporous thin films exhibit increased photocatalytic activities due to their exceptionally high surface area. However the study and the optimization of the photocatalysis in such porous media is not easy to be done due to the fact that the catalytic process is highly dependent from several environmental and structural parameters. The research activities of this thesis were essentially focused on (i) the fabrication of mesoporous TiO2-based photoactive thin films with tunable composition and nanostructure and (ii) their utilization as platform for fundamental study of the photocatalytic process by ellipsometry. The mesoporous films with tunable nanostructure will be fabricated by coupling sol-gel chemistry and highly controlled liquid deposition techniques. Among modern analytical tools, 2D-GISAXS, ellipsometry and ellipso-porosimetry, SEM-FEG, HR-TEM and WAXS, were used to obtain a large set of relevant information. In the first part, a model TiO2 mesoporous film was analysed by ellipsometry for fundamental investigations of the photocatalytic process kinetics in air as function of the environmental and the organic pollutant. The information obtain by ellipsometry has allowed the proposition of photodegradation mechanisms in the studied conditions. In the second part, composite mesoporous TiO2/SiO2 films with tunable optical properties were fabricated by sol-gel chemistry. A structural study on the films porous network and composition was conducted. In-situ ellispometry was also used to study the photocatalytic activity.

L'objectif de la thèse est de mieux comprendre les mécanismes de dégradation photocatalytique se produisant sous air ou sous azote en étudiant la disparition, la minéralisation et les produits intermédiaires d'une molécule simple l'acide acétique. Les réactions sont réalisées sous ces deux atmosphères afin de se placer dans des conditions de dépollution ou de génération d'énergie. L'étude est réalisée en phase gazeuse et sous flux en prenant comme molécule organique une molécule simple l'acide acétique. Dans un premier temps nous avons étudié la dégradation de l'acide acétique en utilisant le photocatalyseur de référence, TiO2 P25. Quel que soit le flux gazeux de réaction, air ou N2, nous avons montré que la réaction de décarboxylation est la première étape de la disparition de l'acide acétique. Cependant, le sort du groupe méthyle dépend du gaz porteur et du débit molaire (en d'autres termes de la concentration du polluant en phase gazeuse). Le mécanisme de dégradation se produisant à la surface du photocatalyseur est alors représenté pour expliquer l'importance de ce mécanisme comparé à celui faisant intervenir les radicaux hydroxyles. La schématisation du mécanisme inclut la régénération du photocatalyseur et la formation possible de H2O2, lequel a été observé dans la littérature. Il est également noté que la sélectivité d'éthane observé sous flux d'air augmente avec la concentration en polluant et correspond à la réaction de deux radicaux méthyl. Comme précédemment la formation de ce composé en surface du TiO2 est proposée. L'étude des produits de dégradation de l'acide acétique marqué par du carbone 13 sur le groupe carbonyle (CH313COOH) suggère que l'acétone et l'acétaldéhyde ne proviennent pas de la réduction du groupe carboxylique. Dans une seconde étape l'impact du flux photonique et de l'humidité en présence de TiO2 P25 et l'effet de différents TiO2 commerciaux sur la conversion et plus particulièrement la distribution des produits intermédiaires ont été étudiés. La comparaison de l'efficacité de différents TiO2 commerciaux a été discutée en considérant la présence de phase rutile, la nature des espèces actives, la surface spécifique de TiO2, le nombre de groupes OH à la surface des catalyseurs, la présence d'impuretés et la porosité des matériaux. Notre étude s'est ensuite focalisée sur la détermination de l'efficacité d'échantillons de TiO2 modifiés par ajout d'or afin d'améliorer la séparation des charges et ainsi la dégradation de polluant en présence d'air ou la formation de produit en présence de flux d'azote. Deux séries de Au/TiO2 avec les mêmes charges d'or (~ 0,16% en poids) ont été préparées par les deux méthodes: pyrolyse laser et pyrolyse par pulvérisation de flamme (Au-TiO2 LP et Au-TiO2 FSP). Les résultats ont montré que la présence d'or améliore l'activité photocatalytique dans l'air dans le cas des échantillons préparés par pyrolyse laser alors qu'aucun effet n'est observé avec les catalyseurs préparés par pyrolyse à flamme (FSP). Ce résultat s'explique en considérant la taille des nanoparticules d'or plus petite dans le cas des échantillons obtenus par pyrolyse laser. L'effet inverse est observé sous atmosphère de N2, la présence d'or diminue de plus de moitié la dégradation de l'acide acétique mais favorise la formation d'éthane. Ce résultat est discuté en considérant la présence d'or sous forme cationique. Malheureusement, par XPS, il n'a pas été possible d'observer d'or probablement dû à sa faible quantité. L'impact du dopage à l'azote de TiO2 LP et Au-TiO2 LP a également été étudié. Ce dopage diminue l'efficacité de cet échantillon. Finalement des études préliminaires ont été conduite d'une part sur l'efficacité de textile lumineux photocatalytique pour dégrader l'acide acétique afin d'améliorer les rendements quantiques et d'autre part sur les efficacités de catalyseurs Ag/TiO2 lesquels, outre diminué la pollution organique permettrait également l'inactivation des microorganismes / The objective of the thesis is to better understand the mechanisms of photocatalytic degradation occurring under air or under nitrogen by studying the disappearance, mineralization and intermediate products of a simple molecule acetic acid. The reactions are carried out under these two atmospheres in gas phase and dynamic mode in order to place themselves under conditions of depollution or of energy generation. Firstly, we studied the degradation of acetic acid using the reference photocatalyst, TiO2 P25. Regardless of the atmosphere, air or N2, we have shown that the decarboxylation reaction is the first step in the disappearance of acetic acid. However, the fate of the methyl group depends on the carrier gas and the molar flow rate (in other words, the concentration of the pollutant in the gas phase). The mechanism of degradation occurring on the surface of the photocatalyst is then represented to explain the importance of this mechanism compared to that involving the hydroxyl radicals. The schematization of the mechanism includes the regeneration of the photocatalyst and the possible formation of H2O2, which has been observed in the literature. The study of the degradation products of acetic acid labelled with carbon 13 on the carbonyl group (CH313COOH) suggests that acetone and acetaldehyde do not result from the reduction of the carboxylic group. In a second step, the impact of photonic flux and moisture in the presence of TiO2 P25 as well as the effect of different commercial TiO2 on the conversion and more particularly the distribution of the intermediate products have been studied. Comparison of the effectiveness of different commercial TiO2s was discussed by considering the presence of rutile phase, the nature of the active species, the specific surface area of TiO2, the number of OH groups on the surface of the catalysts, the presence of impurities and the porosity of the materials

This study investigated the application of advanced oxidative processes for the homogeneous and heterogeneous degradation of a tanning effluent. The catalytic activity of a solid oxide containing manganese was evaluated in the heterogeneous systems. The experiments were performed in a photocatalytic batch reactor in laboratory scale. The solid used was the commercial product Birm®, consisting mainly of crystalline silica, silicate, aluminum and manganese dioxide. The adsorption results using Birm® in synthetic sewage adjusted to the models of Langmuir and Freundlich and established that the adsorption capacity of the Birm ® is low. The synthetic and real tannery effluents were assessed by the degradation kinetics of photochemical homogeneous (H2O2/UV) processes and heterogeneous (UV/H2O2/Birm®) at different pH, concentration of H2O2 and catalyst. The degradation kinetics of the ES followed in law and kinetics order of pseudofirst showing that the Birm® presented no catalytic activity in appreciable color degradation of the synthetic effluent. But when the solid was evaluated for the degradation of the real tannery effluent, it proved to be active, with kinetics of degradation occurring more efficiently than the homogeneous system (H2O2/UV) one. In both effluents there was a catalytic decomposition of hydrogen peroxide. However, the decomposition in ES resulted in inactive products for the catalytic oxidation or free radicals, which possibly were disabled in difusional ways and didn t react with the effluent. The increasing of the concentration of nitrate and sulfate also demonstrated a good the treatment of tanning effluent. / Este estudo investigou a aplicação de processos oxidativos avançados, homogêneos e heterogêneos, na degradação de efluentes líquidos industriais de couro sintético e real. O efluente sintético é uma solução aquosa do corante de couros Acid Orange G. O efluente real é oriundo da indústria de processamento de couro, coletado após o decantador secundário do tratamento por lodos ativados. Os experimentos foram realizados em reator fotocatalítico descontínuo em escala de laboratório. O sólido utilizado como catalisador heterogêneo é um composto comercial denominado Birm®, constituído principalmente de sílica cristalina, silicato de alumínio e dióxido de manganês. A adsorção do efluente sintético sobre o Birm® ajustou-se aos modelos de Langmuir e de Freundlich e, o sólido apresentou baixa capacidade adsortiva. As cinéticas de degradação dos efluentes pelos processos fotoquímicos homogêneo (H2O2/UV) e heterogêneo (UV/H2O2/Birm®) foram avaliadas em diferentes valores de pH, concentração de H2O2 e de catalisador. Os resultados estabeleceram o modelo cinético de pseudoprimeira ordem para a degradação do efluente sintético. O Birm® apresentou atividade catalítica apenas para o efluente de curtume, apesar de a decomposição catalítica do peróxido de hidrogênio ter ocorrido em ambos efluentes. Supõe-se que essa atividade foi potencializada pela diversidade de compostos orgânicos presentes no efluente de curtume. A degradação deste efluente também foi comprovada pelo aumento das concentrações de sulfato e nitrato.

Algal infestation in water bodies causes the release of soluble organic compounds that impact negatively on the taste and odour of the water. With increasing pollution in water bodies and increasing nutrient loading from agricultural activities, most water reservoirs in South Africa and around the world have become affected by this problem. In this study, an advanced oxidation process (AOP), namely, photocatalysis was evaluated for its potential to degrade aromatic compounds; and taste and odour causing bi-cyclic compounds originating from algae. Semiconductor photocatalysis is an environmentally friendly technology requiring no chemical inputs which is capable of completely mineralising organic pollutants to CO2 and H2O thereby eliminating production of unwanted by-products. Although processes involved in the photo-degradation have been reported for a wide range of pollutants, the degradative pathway in this process has not been fully established. In this study, compounds including phenol, 2-chlorophenol, 4-chlorophenol and nitrophenol were successfully eliminated from simulated wastewater. Degradation of geosmin at an environmentally significant initial concentration of 220 ng/L to levels below the lowest detectable concentration was achieved with an optimum catalyst concentration of 60 mg/L at a rate of 14.78 ng/L/min. Higher catalysts loading above 60 mg/L resulted in a decrease in degradation rates. An increase in initial geosmin concentration resulted in a decrease in rates. Ionic species commonly found in surface waters (HCO3 -, and SO4 2-) significantly reduced the efficiency of geosmin degradation. Degradation of geosmin produced acyclic intermediates from ring fission tentatively identified as 3,5-dimethylhex-1-ene, 2,4-dimethylpentan-3-one, 2-methylethylpropanoate and 2-heptanal. The results obtained indicate that the degradation of organic pollutants in aqueous solution is as a result of synergic action from hydroxyl radicals, positive holes and direct photolysis by UV radiation, though the predominant pathway of degradation is via hydroxyl radicals in solution. Major aromatic intermediates of phenol degradation include catechol, resorcinol and hydroquinone produced in the order catechol > resorcinol > hydroquinone. All three are produced within 2 minutes of photocatalytic reaction of phenol and remain in solution until all phenol is degraded in aerated systems. Production of resorcinol in non-aerated systems is transient, further supporting the hydroxyl radical dominant reaction pathway. / Thesis (PhD)--University of Pretoria, 2014. / gm2014 / Chemical Engineering / unrestricted

Une opportunité attrayante consisterait à utiliser l'énergie solaire, abondante et (quasi)inépuisable, pour valoriser le CO2 en carburants. Ceci permettrait de répondre à une double préoccupation : le dérèglement climatique imputable à l’augmentation de la concentration de gaz à effet de serre dans l’atmosphère d’une part, et d’autre part la raréfaction annoncée des ressources en énergie. Les végétaux sont capables de réduire le dioxyde de carbone en composés hydrogénocarbonés et d’oxyder simultanément l’eau en dioxygène par photosynthèse. Cette étude se propose d’élaborer des matériaux capables d’absorber la lumière et d’imiter le processus naturel, notamment son schéma énergétique en Z. La création de systèmes inorganiques comportant des hétérojonctions SCp (cathode) - Métal - SCn (anode) a été envisagée pour répondre à la problématique. Deux stratégies de synthèse ont alors été mises au point afin d’élaborer différents photocatalyseurs composite SCp@M/SCn notamment Cu2O@Pt/TiO2. L’évaluation des performances photocatalytiques a permis de révéler les bénéfices apportés par la présence d’hétérojunctions en termes de séparation des charges photogénérées et de sélectivité quant à la production de composés hydrogénocarbonés par photocatalyse. Ces travaux apportent une pierre importante à l’édifice d’un procédé de « photosynthèse artificielle » / An enticing opportunity would consist in using abundant and inexhaustible solar energy to valorise CO2 into fuels. That might answer in an elegant way to environmental and energetic concerns: the global warming due to atmospheric CO2 concentration increase and the dreaded shortage of energy resources. Green plants are able to reduce carbon dioxide into hydrocarbonated compounds and to oxidise simultaneously water into dioxygen by using photosynthesis. This study will focus on the design of materials able to absorb light and to imitate this natural process and more particularly its typical energetic Z-scheme. The chosen strategy is the creation of inorganic systems with SC-p (cathode) - Metal - SC-n (anode) heterojunctions. Two synthesis strategies were elaborated to obtain composite photocatalysts SCp@M/SCn, and more particularly Cu2O@Pt/TiO2. The evaluation of photocatalytic performances reveals heterojunctions benefits in term of charge separation and selectivity for photocatalytic hydrocarbonated compounds production. This study seems to do its bit towards “artificial photosynthesis” process

Cette thèse s’inscrit dans le développement et l’optimisation d’un panel de catalyseurs dopés ou non dopés pour le traitement des eaux usées par un Procédé d’Oxydation Avancée (POA), la photocatalyse hétérogène solaire. Ce procédé de traitement tertiaire pour la dépollution de molécules organiques biorécalcitrantes est limité par l’absorption des catalyseurs dans le domaine de l’UV ne représentant que 5 % du spectre solaire reçu à la surface de la Terre. L’objectif de ce travail est de comparer les efficacités photocatalytiques sous rayonnement UV, visible et solaire dans le but d’améliorer les efficacités dans le domaine de l’UV, de développer un catalyseur exploitant efficacement le rayonnement visible et de définir les paramètres clés régissant les réponses photocatalytiques. Dans cette optique, une étude a été menée sur les catalyseurs de ZnO dopés ou non dopés. L’ensemble des catalyseurs à base de ZnO ont été synthétisé par un seul et même procédé, le sol-gel couplé à un séchage en conditions supercritiques. Les caractérisations structurales, morphologiques, chimiques, optiques et optoélectroniques ont été réalisées en vue de définir leurs paramètres physico-chimiques pour maitriser les conditions de synthèses des catalyseurs. Elles ont également montré que le ZnO dopé décale sa bande d’absorption vers le domaine du visible. Les expérimentations photocatalytiques ont été conduites à l’aide d’un banc de mesure photocatalytique dans le domaine de l’UV, du visible et du solaire. Une attention particulière est portée sur un polluant modèle, le pyriméthanil. En parallèle, ces expérimentations ont été couplées à un modèle cinétique. Les nanoparticules de Zn1-xMxO (M : Ca, Al, Li, V, In, Co, P…) présentent des réponses photocatalytiques prometteuses dans le domaine du visible. Une corrélation a également été mise en évidence entre les propriétés physico-chimiques des catalyseurs et l’efficacité à produire des radicaux. Par ailleurs, une étude plus approfondie a été menée sur le Zn0,90Ca0,10O. Cette étude révèle la présence de défauts structuraux jouant un rôle essentiel sur les réponses photocatalytiques. / This thesis is part of the development and optimization of a doped and undoped panel of catalysts for the treatment of waste water based on an Advanced Oxidation Process (AOP), solar heterogeneous photocatalysis. This tertiary process for bio-recalcitrant organic molecules clean up is limited by the catalysts absorption in the UV range which represent only 5 % of the solar spectrum received on the earth surface. The aim is to compare photocatalytic efficiency under UV, visible and solar irradiation in order to improve efficiency in the UV range, to develop a catalyst which operates effectively under visible irradiation and to define key parameters governing the photocatalytic activities. In this context, a study is performed on doped or undoped ZnO based catalysts. All of ZnO based catalysts are synthesized by the same process, the sol-gel process under supercritical drying conditions. Structural, morphological, chemical, optical and optoelectronical characterizations is carried out to define their physico-chemical parameters in order to control the synthesis conditions of these catalysts. Doped ZnO also showed an absorption edge shift toward the visible range. Photocatalytic experiments are carried out with a photocatalysis optical bench in the UV, visible and solar range. Particular attention is paid on a model pollutant, pyrimethanil. In parallel, these experiments are coupled to a kinetic model. Nanoparticles of Zn1-xMxO (M : Ca, Al, Li, V, In, Co, P…) showed encouraging photocatalytic activities in the visible range. A correlation is showed between the physico-chemical properties of the catalysts and the radicals production efficiency. Furthermore, an extensive study is done on Zn0,90Ca0,10O. This study reveals the presence of structural defects playing a main role on the photocatalytic activities.

La pollution de l'air intérieur est un enjeu majeur pour la santé humaine. Pour réduire les concentrations de polluants des milieux confinés, notre étude s'est basée sur la conception et les tests d'un nouveau média photocatalytique innovant composé de textile rendu lumineux grâce à la présence de fibres optiques microstructurées. Le textile est rendu photocatalytique après ajout de TiO2 en suivant différentes méthodes de dépôt. Les fibres optiques ont alors deux rôles fondamentaux : premièrement d'être le support du catalyseur et deuxièmement d'être le moyen d'amener le rayonnement UVA au coeur du lit photocatalytique. La rencontre des trois constituants de la photocatalyse, les photons UV, le catalyseur et le polluant, est alors favorisée par l'utilisation de ce type d'échantillon. Les propriétés structurales et optiques de ce nouveau matériau ont été caractérisées par des analyses de surface (microscopie otique et microscopie électronique à balayage environnementale (MEBE)), des mesures d'irradiance UV et des analyses permettant de localiser le TiO2 à la surface de l'échantillon (Raman et MEB‐EDX). L'influence de différents paramètres tels que la structure textile, la méthode de dépôt, les caractéristiques d'irradiation, les débits molaires sur la dégradation de deux composés organiques volatiles, le formaldéhyde et le toluène, a été étudiée et corrélée aux propriétés physicochimiques du matériau / The indoor air pollution is a major challenge for human health. To reduce the concentrations of pollutants in confined area, our study is based on the design and testing of a new innovative photocatalytic media composed of textile which is lighted with microstructured optical fibres. The textile becomes photocatalytic after the coating of TiO2 with different methods. The optical fibers have then two fundamental roles: first to be the catalyst support and secondly to be the light transmission support from the source into the photocatalytic bed. The meeting of the three constituents of photocatalysis (UV photons, catalyst and pollutants) is then enhanced by the use of this type of sample. The structural and optical properties of this new material were characterized by surface analysis (optical microscopy and electronic secondary electron microscopy (ESEM)), with measurements of UV irradiance and methods to determinate the location of the TiO2 on the sample surface (Raman spectroscopy and EDX‐SEM). The influence of different parameters such as textile structure, coating method, irradiation characteristics, molar flow on the degradation of two volatile organic compounds, formaldehyde and toluene, was studied and correlated to the physical‐chemical properties of the material

Orientadores: Peterson Bueno de Moraes, Christiane de Arruda Rodrigues Ragnini / Dissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Tecnologia / Made available in DSpace on 2018-08-27T04:30:52Z (GMT). No. of bitstreams: 1 Souza_EdivaldoLuisde_M.pdf: 3079610 bytes, checksum: a78db6078a721c74f963b944bae72f47 (MD5) Previous issue date: 2015 / Resumo: A sociedade e seus processos produtivos têm gerado e lançado quantidades elevadas e diversificadas de compostos orgânicos, inorgânicos e biológicos no meio ambiente. Juntamente com as emissões naturais, houve um grande acúmulo destes materiais nos diferentes compartimentos ambientais. A produção e o uso de medicamentos, como hormônios e antibióticos contribuíram muito para a ampliação deste quadro. Por serem persistentes não são totalmente metabolizados nos seres vivos e acabam sendo excretados e lançados em corpos receptores. Os mecanismos naturais de degradação e métodos de tratamento convencionais de efluentes não são suficientemente eficientes na remoção completa destes compostos; em função disso, é necessário o desenvolvimento e aplicação de tecnologias alternativas para a redução destes impactos. Entre estas tecnologias podemos citar os Processos Oxidativos Avançados (POA) que são mais eficientes para o tratamento destes tipos de efluentes. Objetivamos neste trabalho desenvolver, caracterizar e utilizar eletrodos nanoestruturados de TiO2 para a confecção de um reator fotoeletroquímico para a degradação do antibiótico amoxicilina e do citrato de sildenafil, este último, princípio ativo do medicamento Viagra®, submetidos à radiação UV e solar. Foram desenvolvidos eletrodos nanoestruturados com TiO2 sobre substrato de titânio, a partir de processos de anodização eletroquímica, na qual foram variados diferentes parâmetros que influenciaram nas características dos nanotubos de TiO2 desenvolvidos. Os nanotubos formados foram avaliados por Microscopia Eletrônica de Varredura quanto ao comprimento, espessura de parede e homogeneidade de distribuição. Testou-se contra-eletrodos de platina, Anodo Dimensionalmente Estável (ADE), níquel, aço-inoxidável 304 e 316L e obteve-se nanotubos de TiO2 com comprimentos entre 100 e 650 nm. Observou-se na maioria dos eletrodos nanoestruturados uma distribuição homogênea dos nanotubos. Visando a obtenção de nanoestruturas mais fotoativas, realizou-se cristalização por aquecimento em estufa. Na cristalização dos nanotubos, as análises de Difratometria de Raios-X evidenciaram intenso sinal no ângulo 2? próximo a 25º para todas as amostras significando que os nanotubos de TiO2 se cristalizaram na fase anatase, a qual é mais fotoativa. A degradação de amoxicilina apresentou rendimento de aproximadamente 85% em um intervalo de 4 horas de tratamento, enquanto que o rendimento na degradação do citrato de sildenafil foi de aproximadamente 88%, para um volume de amostra de 160,0 mL etanol/água destilada à 20% V/V em Na2SO4 0,1 M, concentração do fármaco de 10,0 mg L-1, lâmpada de vapor de mercúrio, WUV=13 W/m2, disposição horizontal dos eletrodos, distância de 3,0 mm entre lâmpada e ânodo de TiO2, cátodo de platina em tela, tensão de 1,5 volts, anodo de titânio nanoestruturado obtido a partir de contra-eletrodo de ADE 70%TiO2/30%RuO2 com d = 5,0 mm a 700 rpm e t = 120 min, 2 horas de tratamento. As nanoestruturas apresentaram-se com baixa resistência mecânica em relação à aplicação de valores de potencial elétrico superiores a 1,5 V. No entanto, abaixo destes valores, as estruturas de TiO2 mostraram-se altamente estáveis em relação à durabilidade. A eletrólise apresentou eficiência insignificante na degradação do fármaco citrato de sildenafil, sendo então aplicado um potencial aos eletrodos para fotoassistir ao processo fotocatalítico o qual se mostrou fortemente dependente da drenagem eletrônica / Abstract: The modern society and its production processes have generated and released high amounts of synthetic organic compounds which accumulate in different environmental compartments. The production and use of drugs such as hormones and antibiotics have greatly contributed to the expansion of this problem. Due to persistent-profile of these drugs, they are not completely metabolized and the conventional Wastewater Treatment Plants are not fully effective for the removal of these compounds. Thus, the development and application of alternative technologies is needed. In the other hand, the Advanced Oxidation Processes (AOP) has been effective for the treatment of pharmaceutical residues. This work aimed to produce, characterize and use nanostructured TiO2 electrodes and an photoelectrochemical reactor for the degradation of the antibiotic amoxicillin and sildenafil citrate, the latter, the active ingredient of Viagra©. The experiments were carried out using ultraviolet (UV) and solar radiation. Nanostructured TiO2 electrodes were developed from titanium substrate by electrochemical anodization process in which the different parameters were varied in order to verify its influence on the length, thickness and uniformity of distribution of TiO2 nanotubes formed, evaluated by Scanning Electron Microscopy. It was tested different counter-electrodes such as platinum, dimensionally stable anode (DSA), nickel, stainless-steel 304 and stainless-steel 316L and were obtained TiO2 nanotubes with lengths between 100 and 650 nm. It was observed in most nanostructured electrodes a homogeneous distribution of the nanotubes. Also, in order to obtain nanostructures more photoactive, crystallization was performed by heating in an oven. After crystallization process, analysis of X-Ray diffraction showed intense signal at 2? close to 25º for all samples, meaning that the TiO2 nanotubes were crystallized in the anatase phase which is more photoactive. Photocatalytic experiments with the Amoxicillin solution resulted in approximately 85% of degradation in 4 hours of treatment, whereas the degradation of sildenafil citrate was about 88%. The samples consisted of 160.0 mL ethanol / distilled water at 20 % V/V in 0.1 M Na2SO4, drug concentration of 10.0 mg L-1. The experimental setup consisted of a mercury vapor lamp or a solar simulator, horizontal arrangement of the electrodes and a platinum screen cathode. It was applied 1.5 volts, distance of 3,0 mm between the lamp and TiO2 nanostructured anode, obtained from the anodization using a DSA (70%TiO2/30%RuO2) counter-electrode placed at 5.0 mm, under stirring of 700 rpm over 120 minutes. The nanostructures had low strength to the application of higher electrical potential values than 1.5 V. However, below this value the TiO2 structures were more stable and with greater durability. Electrolytic process had a negligible efficiency in the degradation of sildenafil citrate; thus the applied potential was more important to help the photocatalytic process, which is strongly dependent of the electronic drainage / Mestrado / Tecnologia e Inovação / Mestre em Tecnologia

Composite materials formed from two or more functionally different materials offer a versatile avenue to create a tailored material with well defined traits. Within this dissertation research, multi-functional composites were synthesized based on organic and inorganic materials. The functionally of these composites was experimentally tested and a semi-empirical model describing the sedimentation behavior of these particles was developed. This first objective involved the fabrication of microcomposites consisting of titanium dioxide (TiO2) nanoparticles confined within porous, microgels of a thermo-responsive polymer for use in the photocatalytic treatment of wastewater. TiO2 has been shown to be an excellent photocatalyst with potential applications in advanced oxidative processes such as wastewater remediation. Upon UV irradiation, short-lived electron-hole pairs are generated, which produce oxidative species that degrade simple organic contaminants. The rapid sedimentation of these microcomposites provided an easy gravimetric separation after remediation. Methyl orange was used as a model organic contaminant to investigate the kinetics of photodegradation under a range of concentrations and pH conditions. Although after prolonged periods of UV irradiation (~8-13 hrs), the titania-microgels also degrade, regeneration of the microcomposites was straightforward via the addition of polymer microgels with no loss in photocatalytic activity of the reformed microcomposites. The second objective within this dissertation involved the systematic development of abrasive microcomposite particles containing well dispersed nanoparticles of ceria in an organic/inorganic hybrid polymeric particle for use in chemical mechanical polishing/planarization (CMP). A challenge in IC fabrication involves the defect-free planarization of silicon oxide films for successful multi-layer deposition. Planarization studies conducted with the microcomposites prepared in this research, yield very smooth, planar surfaces with removal rates that rival those of inorganic oxides slurries typically used in industry. The density and size of these ceria-microgel particles could be controlled by varying the temperature or composition during synthesis, leading to softer or harder polishing when desired.