Propõe-se, pela primeira vez, a associação do tratamento fotocatalítico de amostra, direcionado à degradação e/ou eliminação de interferentes orgânicos, com a separação analito/matriz via geração de hidretos voláteis seguida de determinação por espectrometria de absorção atômica (HG-AAS). O fotocatalisador TiO2 (P-25) foi utilizado sempre em suspensão na amostra, e como fonte de radiação UV empregou-se lâmpada de mercúrio. Duas geometrias de reator fotocatalítico foram examinadas: irradiação estacionária de amostras contidas em cubetas de quartzo (3,5 mL); e irradiação em reator tubular constituído de bobina de Teflon montada em torno da lâmpada. Para avaliar a eficiência do tratamento sob diferentes condições, utilizou-se inicialmente o sistema-modelo Cd(II)-EDTA, com detecção do Cd(II) não quelado por voltametria de pulso diferencial em eletrodo de gota pendente de mercúrio, sabidamente não influenciada pelo TiO2 em suspensão. Nos estudos com HG-AAS, focalizou-se a aplicação do tratamento fotocatalítico à decomposição da arsenobetaína (Asb), um composto modelo interessante por ser refratário aos tratamentos convencionais (micro-ondas + digestão ácida). As condições selecionadas para a etapa de HG-AAS foram: concentração de HCl, 3 mol.L-1, concentração de NaBH4, 1% m/v em NaOH 0,1 mol.L-1, volume de amostra, 0,10 mL e temperatura do atomizador de tubo de quartzo, 980 °C. Nessas condições, as curvas de calibração obtidas por HG-AAS para As(III) e As(V) na faixa de 0,020 a 0,100 mg.L-1 (20 a 100 ppb) apresentaram linearidade e sensibilidade próximas, indicando eficiência de formação similares, característica esta favorável à quantificação total de arsênio em aplicações futuras a amostra reais. Estudos preliminares mostraram que a taxa de recuperação do arsênio é maior no tratamento fotocatalítico realizado em meio alcalino, (pH=12) em razão da menor tendência à adsorção de arsênio em TiO2 nesse meio frente ao neutro e ácido. Parâmetros como o tempo de irradiação, concentração do fotocatalisador e de Asb, além da influência de O2 molecular como scavenger de elétrons também foram investigados. Nas condições selecionadas, partindo-se de uma solução de Asb 0,075 mg.L-1 em arsênio, alcançou-se recuperação aproximada de 80% mediante irradiação por 15 minutos e de 100% após 45 minutos. A decomposição da Asb pelo método fotocatalítico proposto foi confirmada por espectrometria de massa com ionização por electrospray e estudos adicionais poderão revelar se as espécies de arsênio envolvidas na geração da arsina encontram-se completamente mineralizadas. / The combination of photocatalytic sample preparation, aiming degradation of organic interferences, with analyte/matrix separation by generation of volatile hydrides followed by atomic absorption spectrometric determination (HG-AAS) is proposed for the first time in this work, mainly devoted to the investigation of total arsenic analysis. A mercury lamp served as source of UV-radiation and the photocatalyst, TiO2 (P25), was used as a suspension in the sample solution. Two geometries of photocatalytic reactor were examined: stationary irradiation of a set of samples contained in 3.5 mL quartz cuvettes (preferred one for the present application) and stopped-flow irradiation of a sample in a tubular reactor consisting of a Teflon tube coiled around the lamp. Evaluation of the digestion efficiency of the reactors under different conditions was made with help of the model system Cd(II)-EDTA, with detection of the unchelated Cd(II) by differential pulse voltammetry with the hanging mercury drop electrode, known to work in the presence of TiO2 suspension. The subsequent studies in combination with HG-AAS focused on the photocatalytic degradation of arsenobetaine (Asb), chosen as a model because it is particularly resistant to conventional treatments (microwave + acid digestion). The following conditions were established for the HG-AAS step: HCl concentration (3 mol.L-1) and NaBH4 concentration (1% m/v in NaOH 0,1 mol.L-1), sample volume (0.10 mL) and atomization temperature (980 °C). Calibration curves for As (III) and As (V) by HG-AAS in the range of 0,020 to 0,100 mg.L-1 (20 a 100 ppb) conveyed in slope and linearity, indicating the same efficiency of arsine formation from both species, favoring the total quantification of arsenic in the sample. Alkaline medium (pH=12) was preferred for the photocatalytic digestion because recoveries of arsenic were better than in neutral or acidic medium, possibly due to lower losses by adsorption of arsenic species on TiO2. The effects of parameters such as irradiation time, concentration of the photocatalyst and of arsenobetaine, as well as the influence of molecular O2 as an electron scavenger were investigated. Under selected conditions and for a starting solution of 0,075 mg.L-1 Asb an arsenic recovery of 80% approximately was obtained after 15 minutes of irradiation while full recovery required 45 minutes. The decomposition of the Asb molecule after irradiation was confirmed by electrospray mass spectrometry and a further study may reveal if the arsenic species involved in the arsine generation are fully mineralized ones.

Des films multicouches à base de nanoparticules de TiO2 et d’Ag ont été construits sur des substrats modèles et des textiles via la technique du Layer-by-Layer (LbL). Les films à base de nanoparticules de TiO2 construits sur substrats modèles ont montré un comportement photocatalytique non conventionnel pour la minéralisation de l’acide formique en phase gaz sous irradiation UV-A, et une minéralisation très importante a été obtenue avec un film possédant une unique couche de nanoparticule de TiO2. Ces films ont également montré des propriétés biocides sous irradiation UV-A. La mise en œuvre d’une méthode one-pot, combinant la synthèse photo-induite des nanoparticules d’Ag et dépôt de la couche de TiO2 par LbL, a permis la synthèse de nanoparticules d’Ag directement au sein des films et une exaltation très importante des propriétés photocatalytiques des films. Les méthodes de constructions ont été transférées avec succès sur textiles. Les films restent photocatalytiquement actifs et biocides sous irradiation UV-A après plusieurs cycles de lavages. / TiO2 and Ag nanoparticle multilayered films were constructed on model substrates and textiles via Layer-by-Layer (LbL) assembly. The TiO2 nanoparticle based films constructed on model substrates showed a non-conventional photocatalytic behaviour for gas phase formic acid mineralisation upon UV-A irradiation, and a high mineralisation was obtained for a single layer TiO2 nanoparticle film. These films also showed biocidal properties upon UV-A irradiation. The elaboration of a one-pot method, combining the photo-induced synthesis of Ag nanoparticles and the LbL deposition of TiO2 nanoparticle layer, allowed the direct synthesis of Ag nanoparticles within the films and a high enhancement of the film photocatalytic properties. The construction methods were successfully transfered on textile surfaces. The films were photocatalytically active and biocidal under UV-A irradiation after several washing treatment cycles.

Afin de réduire la teneur en soufre des essences, l’hydrodésulfuration transforme les molécules soufrées en hydrocarbures en présence d’un catalyseur supporté (métaux de transition sulfurés : MoS2) et dopé (Co, Ni). Cette phase active, déposée sur des nanoparticules, présente un nombre plus important de défauts, sites actifs essentiels à la catalyse. Les nanoparticules ont un ratio S/V élevé, une grande réactivité de surface avec une juste utilisation des quantités de métaux. L’objectif de ce projet de thèse est de synthétiser des catalyseurs nanométriques de type coeur@coquille possédant une meilleure activité catalytique qu’un simple mélange mécanique de deux métaux sulfurés. Le coeur est composé de Fe3O4 ou de nanodiamants et la coquille de MoS2, NiMoS, CoMoS ou NiCoMoS, supporté sur du TiO2 ou de la γ-Al2O3. Une réaction modèle (HDS du thiophène) a été utilisée afin d’évaluer l’activité catalytique et d’optimiser la structure du catalyseur. L’étude portera sur les paramètres de synthèse et l’effet de la taille du coeur, la synthèse utilisée, les interactions entre le coeur et la coquille, le support, la (co)– promotion (Ni/Co) et l’activation par la température. / In hydrodesulfurization of fossil fuels, the sulfur levels are reduced by sulfur extraction from hydrocarbons by using supported catalysts (MoS2), doped (Co, Ni). Ultra-deep hydrodesulfurization will be achieved by improving new catalysts. Nanoparticles are a promising candidate with their high S/V ratio and permit to use the precise amount of metallic sulphide. The aim of this thesis is the synthesis of core@shell nanometric catalyst with improved activities. Core composed of Fe3O4 or nanodiamonds will be surrounded by a shell formed of MoS2, NiMoS, CoMoS or NiCoMoS, supported on TiO2, γ-Al2O3. Model reaction (thiophene) has allowed to compare conversion rates between each catalyst. Additionally, characterizations have provided a better understanding of the HDS catalyst structure and performances. Some factors have been investigated such as the size of the core, theinteractions between the core and the shell, the type of synthesis, the support chosen, the synergetic effect with doping ions and also the activation of the catalyst at low temperature.

Made available in DSpace on 2014-12-17T15:42:13Z (GMT). No. of bitstreams: 1 WilliamGM_DISSERT.pdf: 1986302 bytes, checksum: 71e6a449a8f77e2f64a9c3908ab5410d (MD5) Previous issue date: 2013-07-30 / Coordena??o de Aperfei?oamento de Pessoal de N?vel Superior / A new self-sustainable film was prepared through the sol-gel modified method, previously employed in our research group; sodium alginate was used as the polymer matrix, along with plasticizer glycerol, doped with titanium dioxide (TiO2) and tungsten trioxide (WO3). By varying WO3 concentration (0,8, 1,6, 2,4 and 3,2 μmol) and keeping TiO2 concentration constant (059 mmol), it was possible to study the contribution of these oxides on the obtained films morphological and electrical properties. Self-sustainable films have analyzed by Fourier Transform Infrared Spectroscopy (FTIR), X-Ray Diffraction (XDR), Scanning Electron Microscope (SEM), Energy Dispersive X-ray Spectroscopy (EDS) and Electrochemical Impedance Spectroscopy (EIS). By the IR specters, it was possible identify the TiO2, and posteriorly WO3, addition has provided dislocation of alginate characteristics bands to smaller vibrations frequencies indicating an electrostatic interaction between the oxides and the polymer matrix. Diffractograms show predominance of the amorphous phase in the films. SEM, along with EDX, analysis revealed self-sustainable films showed surface with no cracks and relative dispersion of the oxides throughout the polymer matrix. From Impedance analysis, it was observe increasing WO3 concentration to 2,4 μmol provided a reduction of films resistive properties and consequent improvement of conductive properties / Um novo filme autossustent?vel foi preparado, atrav?s do m?todo sol-gel modificado, anteriormente empregado no nosso grupo de pesquisa, utilizando como matriz polim?rica o alginato de s?dio, juntamente com o plastificante glicerol, dopado com di?xido de tit?nio (TiO2) e tri?xido de tungst?nio (WO3). Variando as concentra??es do WO3 (0,8, 1,6, 2,4 e 3,2 μmol), e mantendo constante a concentra??o do TiO2 (0,59 mmol), foi poss?vel estudar a contribui??o destes ?xidos nas propriedades morfol?gicas e el?tricas dos filmes obtidos. Os filmes autossustent?veis foram caracterizados atrav?s das t?cnicas de Espectroscopia de Infravermelho com Transformada de Fourier (FTIR), Difratometria de Raios X (DRX), Microscopia Eletr?nica de Varredura (MEV), Espectroscopia de Raios X por Dispers?o de Energia (EDS) e Espectroscopia de Imped?ncia Eletroqu?mica (EIE). Atrav?s dos espectros de FTIR foi poss?vel identificar que a adi??o do TiO2 e, posteriormente, do WO3 proporciona deslocamento das bandas caracter?sticas do alginato para menores frequ?ncias de vibra??o, indicando uma intera??o eletrost?tica dos ?xidos com a matriz polim?rica. Os difratogramas evidenciaram a predomin?ncia do comportamento amorfo nos filmes. As an?lises de MEV, juntamente com as de EDS, revelaram que os filmes autossustent?veis apresentam uma superf?cie sem trincamento e de relativa dispers?o dos ?xidos ao longo da matriz polim?rica. Atrav?s da EIE observouse que o aumento da concentra??o de WO3 at? 2,4 μmol proporcionou uma redu??o do comportamento resistivo dos filmes, e consequente melhoria em suas propriedades condutoras

Le sujet de la thèse porte sur l'élaboration de nouveaux matériaux MOx (M=Ti,Zr) nanostructurés et fonctionnalisés en surface pour l'élimination des micro-polluants HAP dans des effluents aqueux. Compte tenu de la nature des polluants visés, nous avons choisi de travailler sur des fragments organiques (R) mono- ou poly-aromatiques, pouvant former des complexes de transfert de charge (π-stacking) avec les HAPs en solution, étant donné que ces interactions sont effectives en milieu aqueux. Dans le but d'obtenir un greffage efficace et pérenne, nous avons sélectionné des greffons phosphonates R-P(O)(OH)2 plutôt que carboxylates R-COOH. Ce projet a donc consisté en l'élaboration de différents ligands de type acides phosphoniques comportant au moins une insaturation via une addition d'Aza-Michael. La modification de précurseurs hétéroleptiques a pu conduire à la formation de matériaux hybrides en une seule étape par le procédé sol-gel. Cette approche moléculaire « bottom-up & one pot » a permis l'obtention de nanoparticules cristallisées (pour le titane) et fonctionnalisées en surface de façon contrôlée. Ces nanomatériaux ont ensuite été évalués, seuls ou supportés sur textiles, pour l'élimination de 16 HAP (considérés prioritaires par l'agence américaine EPA). Les matériaux nanocomposites (textiles / oxyde) fonctionnalisés ont démontré les mêmes performances d'adsorption des HAPs que les poudres hybrides nano-structurés, tout en apportant l'avantage supplémentaire de traiter efficacement de plus grands volumes d'eaux pollués en un temps plus court. Enfin ces matériaux peuvent être recyclés ce qui est totalement impossible avec les matériaux carbonés usuels du type charbon actif / The subject of the thesis concerns the elaboration of new hybrid nanomaterials Mox (M=Ti, Zr)n for the elimination of PAH micro-pollutants in aqueous effluents. Taking into account the nature of such pollutants, we chose to work on organic fragments (R) mono- or poly-aromatic, which could form complexes or transfer (p-stacking) with the HAPs in solution, given that these interactions are effective in aqueous media. In order to obtain an effective and long-lasting grafting, we selected phosphonates R-P (O)(OH)2 ligands rather than carboxylates ones R-COOH. This poject thus consisted of the elaboration of different ligands of phosphonic acid containing at least one insaturation via an Aza-Michael addition. Heteroleptic molecular precursors were obtained by reaction between metallic alkoxides and various phosphonic acids, and led us hybrid nanomaterials in a single stage by sol-gel process. This molecular approach “bottom-up & one pot” allowed the obtaining of crystallized nanoparticles (for the titanium) and the control of the surface functionalization. The performances of these nanomaterialsThe performances of these nanomaterials were then tested, alone or supported on fabrics, for the elimination of HAP (considered as priority by the American agency EPA). The results of adsorption of the HAPs on the various synthesized nanomaterials show an exceptional efficiency of materials to adsorb 16 HAPs. The nanocomposite materials (textile/oxides) demonstrated the same performances of adsorption of the HAPs as the hybrid nano-structured powders, while bringing the additional benefit to treat effectively bigger volumes of waters polluted within shorter time. Finally these materials can be recycled which is totally impossible with the usual carbon materials such as activated charcoal

Ce travail s’intéresse à la synthèse de films minces composites Zn-Si-O et Ti-Si-O à l’aide d’un procédé hybride combinant le dépôt de silice par PECVD (Plasma Enhanced Chemical Vapour Deposition) à partir du précurseur organométallique hexaméthyldisiloxane (HMDSO-Si2C6H180), et la pulvérisation réactive de zinc ou de titane. L’élaboration de revêtements dont la composition s’échelonne d’un oxyde métallique ZnOx ou TiOx à la silice est rendue possible en agissant sur le débit du précurseur. L’ajout de silicium dans le revêtement fait évoluer sa morphologie de colonnaire à dense. De plus un phénomène de compétition entre les composantes PECVD et pulvérisation du procédé est mis en évidence. Ainsi la mesure des vitesses de dépôt en fonction du débit d’HMDSO permet de déterminer les valeurs de débits critiques de précurseurs à partir desquelles le dépôt de silice par PECVD est initié, et pour lesquelles le recouvrement de la cible par le dépôt de silice se produit. Les caractérisations des revêtements montrent que ceux-ci sont constitués, dans une zone proche de l’interface avec l’acier d’un mélange d’oxydes non stoechiométriques qui diffère de manière importante d’un mélange ZnO+SiO2 ou TiO2+SiO2. Pour les revêtements de type Ti-Si-O le titane est en excès dans la zone proche de l’interface tandis que dans les revêtements de type Zn-Si-O le silicium est en excès. On observe alors une décroissance progressive de la concentration atomique respectivement de titane et de silicium lorsqu’on approche de la surface du revêtement. Ces évolutions peuvent être reliées à un effet de l’augmentation de la température dans la première phase de l’élaboration, qui agit sur la cinétique de dépôt par PECVD et conditionne l’état de contamination de la cible / The present work deals with the synthesis of Zn-Si-O and Ti-Si-O composite thin films by a hybrid process. The coatings are prepared by combining PECVD (Plasma Enhanced Chemical Vapour Deposition) of silicon oxide from hexamethyldisiloxane (HMDSO-Si2C6H180) and reactive sputtering of a zinc or a titanium target. Any composition of the deposited layer can be obtained from zinc oxide or titanium oxide to silicon oxide, by controlling the HMDSO flow rate in the reactor. The morphologies evolve from columnar to dense by adding silicon in the coating. Moreover, a competitive deposition process takes place between PECVD and sputtering. The critical flow rates above which the PECVD silicon oxide deposition takes place on the substrate and on the target can be described from measurements of the thin film deposition rates as a function of the HMDSO flow rate. The coating caracterisations show that they are, near the coating-substrate interface, made of a mixture of non-stoechiometric oxides whose composition is different from a ZnO+SiO2 or a TiO2+SiO2 mixing. Titanium and silicon are in excess near the coating-substrate interface, respectively in the Ti-Si-O and Zn-Si-O thin films. Then the atomic concentrations of titanium and silicon progressively decrease when reaching the surface of the thin film. These behaviours are correlated with an increase of the temperature during the first phase of deposition that increases the PECVD deposition kinetics and determines the contamination state of the target

Ce travail rapporte l'élaboration par voies humides (sol-gel, précipitation) et sèche (mécanosynthèse) de photocatalyseurs originaux à l’état de poudre pure ou supportées sur des fibres de palygorskite (Pal), composant d’une argile brute naturelle d’origine marocaine. TiO2 seul, non dopé ou dopé au soufre, et couplé avec CuO fut utilisé comme composant actif principal. Ag2CO3 fut également étudié comme composant alternatif en raison de sa forte activité dans le domaine du visible. Ces photocatalyseurs furent testés pour la dégradation de polluants modèles anionique (orange G, OG) et cationique (rouge neutre, RN) en milieux aqueux, sous irradiation artificielle UV, Visible et Solaire, ainsi que sous ensoleillement naturel extérieur. Les caractérisations multi-échelles effectuées sur les différents photocatalyseurs développés ont essentiellement démontré : - L’immobilisation par sol-gel de nanoparticules (NPs) de TiO2 et CuO sur Pal avec formation d’hétérojonctions entre ces oxydes, produisant une activité photocatalytique sous UV avérée mais toutefois trop limitée ; - La formation par précipitation de nanocomposites à base de NPs Ag2CO3 déposées sur les fibres de Pal. Selon la durée de maintien des réactifs en digestion et un protocole de cycles thermiques couplés à du vieillissement sous atmosphère de CO2, il a été possible d’obtenir Ag2CO3 sous sa forme structurale métastable hexagonale (H) et stable monoclinique (m), ou de contrôler la proportion des 2 phases dans les composites Ag2CO3/Pal. Ces nouveaux photocatalyseurs sont actifs dans le visible et les nanocomposites biphasés H+m se sont avérés plus actifs que les monophasés. - L’élaboration par mécanosynthèse de TiO2 anatase supporté sur Pal et de TiO2 principalement anatase en coexistence remarquable avec une phase monoclinique métastable B dans le cas du dopage au soufre. TiO2-S est très actif dans le visible tandis que TiO2-Pal manifeste une activité sous UV en présentant l’avantage de pouvoir exploiter les propriétés de l’argile pour développer une multifonctionnalité (photocatalyse-adsorption). Ces photocatalyseurs sont actifs sous forme de poudres dispersés et de revêtements sous irradiation solaire. La cinétique de dégradation du polluant modèle a pu être modélisée. / This work reports the development of different photocatalysts using either wet route (sol-gel and precipitation methods) or dry route (mecanosynthesis followed by annealing). The photocatalysts are TiO2 (pure or doped with sulfur) nanoparticles (NPs), TiO2 coupled with CuO and Ag2CO3 supported on natural fibrous clay from Morocco called palygorskite (Pal). The degradation of model anionic dyes (orange G, OG) and cationic dyes (neutral red, NR) in aqueous solution were investigated under artificial radiation (UV and visible) and natural sunlight. The multi-scale chemical and structural characterization and the properties investigated on the different photocatalysts showed the following results: -Immobilization of both TiO2 and CuO NPs on palygorskite by sol-gel method. Despite the heterojunctions between these functional oxides the photocatalysts exhibit a limited activity under UV irradiation. - Elaboration of nanocomposites made of Ag2CO3 NPs deposited on Pal fibers using the precipitation method. Depending on the time of reactant digestion, the number of thermal cycles and the aging for several months, Ag2CO3 adopts remarkably, in these nanocomposites, the exclusive forms of metastable hexagonal structure (H), or the stable monoclinic one (m) or a mixture of both phases with different proportions depending on the mass ratio of Ag2CO3/Pal. All Ag2CO3-Pal nanocomposites are active in the visible range for the elimination of OG. The nanocomposites in the biphasic form H + m are more active than single phases samples either in the form H or m. - Preparation of anatase TiO2 supported on Pal and TiO2 as a mixture of mainly TiO2 anatase and a minority of a remarkable monoclinic phase B by a mechanical alloying method. The NPs surfaces of these photocatalysts are acidified by grafting the sulfate groups (SO42-) and the anionic network is lightly doped with substituting O2- by S2-. These specific characteristics have made TiO2-S very active in the visible for the degradation of OG, while TiO2-Pal composite exhibits an activity under UV. Both types of photocatalysts in the form of powders dispersed in the OG solutions have proved to be active under sunlight and as well in the form of coating. TiO2-Pal has showed allows the adsorption of cationic entities RN facilitating their subsequent photodegradation.

Tecnologias efetivas para o tratamento de águas e efluentes representam um dos grandes desafios da nossa sociedade; dentre as opções, a fotoeletrocatálise pode ser considerada como uma técnica alternativa e de interesse. Nesse contexto, o presente trabalho teve como objetivo desenvolver eletrodos de TiO2 modificados visando o tratamento fotoeletrocatalítico de interferentes endócrinos. Realizou-se inicialmente a síntese de nanotubos de TiO2 (TiO2-NT) sobre substrato de Ti metálico via anodização eletroquímica em eletrólito NaH2PO4/HF. Para minimizar as limitações inerentes ao TiO2 realizou-se a eletrodeposição de WO3 sobre os nanotubos de TiO2 (Ti/TiO2-NT/WO3) e diretamente sobre o substrato de Ti metálico. Este último revelou a formação de uma camada fina de TiO2 sobre a superfície, posterior ao tratamento térmico, formando um compósito (Ti/TiO2/WO3). A análise de difração de raios-X confirmou a formação da fase monoclínica de WO3 para ambas as sínteses e a fase anatase para os eletrodos de Ti/TiO2-NT/WO3. Para as duas sínteses, as medidas de energia dispersiva de raios-X revelaram uma quantidade crescente de W na composição dos eletrodos com o aumento do tempo de eletrodeposição. Teores elevados de W (acima de 1,2 %) apresentaram uma diminuição expressiva nos valores de fotocorrente. No entanto, baixos teores de W (entre 0,4 e 1,2 %) indicaram um aumento de 20 % nos valores de fotocorrente para os eletrodos de Ti/TiO2-NT/WO3 (20 mA cm-2) e Ti/TiO2/WO3 (17 mA cm-2) comparados aos não modificados, no potencial de +2,0 V. As análises de reflectância difusa mostraram uma baixa energia de bandgap (≈ 2,90 eV, eletrodos de Ti/TiO2-NT/WO3) e um aumento na absorção da irradiação UV-Vis. Posteriormente, os eletrodos modificados foram aplicados na oxidação fotoeletrocatalítica (FE) dos compostos bisfenol-A (BPA) e propilparabeno (PPB), sob irradiação UV-Vis. O método FE apresentou um excelente desempenho em condições ácidas, aplicando-se potencial de +1,50 V e +0,50 V para os eletrodos Ti/TiO2-NT/WO3 e Ti/TiO2/WO3, respectivamente. A mineralização dos compostos BPA e PPB foi superior a 80 % tanto para o Ti/TiO2-NT/WO3 como para o Ti/TiO2/WO3. Quanto à taxa de remoção, o BPA e PPB foram completamente removidos após 45 e 60 min, respectivamente, para os eletrodos de Ti/TiO2/WO3 e após 30 minutos para os eletrodos de Ti/TiO2-NT/WO3. Adicionalmente, os eletrodos apresentaram um baixo consumo energético e boa estabilidade química. Comparada à técnica de fotocatálise (FC), a FE revelou uma eficiência de mineralização 2 vezes superior para o Ti/TiO2-NT/WO3 e mais de 20 % superior para o Ti/TiO2/WO3. Logo, as modificações dos eletrodos de TiO2 com WO3 constituíram importantes contribuições para o desempenho dos materiais, sendo um passo importante para a aplicação em tratamentos alternativos de descontaminação de águas residuárias. Ainda foi de interesse neste trabalho propor um método para a inserção de nanotubos (TiNT) e nanofolhas (TiNS) de titanatos no interior de nanotubos de TiO2 via eletroforese. O estudo possibilitou o desenvolvimento de um método simples e eficiente para a modificação de nanoestruturas complexas. A movimentação do contra eletrodo sobre a superfície do eletrodo de trabalho, adaptado com uma escova nas laterais, reduziu a espessura da camada de TiNS/TiNT. O potencial aplicado (20 V) e a estimulação mecânica da superfície foram importantes para a incorporação das nanoestruturas dentro dos poros de TiO2-NTs. Como resultado, os eletrodos apresentaram um aumento da hidrofobicidade e uma melhora na capacidade de oxidação direta comparado ao eletrodo não modificado. / Effective technologies for the water and wastewater treatment represent a challenges for our society; among the options, the photoelectrocatalysis can be considered a promising and interesting alternative. In this context, the objective of this study was to develop modified TiO2 electrodes for the photoelectrocatalytic treatment of endocrine disruptors. The synthesis of TiO2 nanotubes (TiO2-NT) on metallic Ti substrate was carried out via electrochemical anodization in NaH2PO4 /HF electrolyte. In order to minimize the limitations inherent of TiO2, the electrodeposition of WO3 was performed on the TiO2 nanotubes (Ti/TiO2-NT/WO3) and also in the metallic Ti substrate. The deposition on the Ti metallic produced a thin layer of TiO2 on the surface, subsequent to the heat treatment, generating a composite (Ti/TiO2/WO3). The X-ray diffraction analysis (XRD) confirmed the monoclinic phase of WO3 for both the syntheses and the anatase phase of TiO2 for the Ti/TiO2-NT/WO3 electrodes. For the two syntheses, the X-ray dispersive energy (EDX) analisys indicated an increasing amount of tungsten (W) in the composition of the electrodes with increasing of electrodeposition time. High W content (above 1.2%) showed a significant decrease in the photocurrent values. However, low content of W (between 0.4 and 1.2 %) indicated an increase of 20 % in the photocurrent values for the electrodes Ti/TiO2-NT/WO3 (20 mA cm-2) and Ti/TiO2/WO3 (17 mA cm-2) compared to the unmodified ones, at the potential of +2.0 V. Difuse reflectance analysis indicated low bandgap energy (≈ 2.90 eV, Ti/TiO2-NT/WO3 electrodes) and an increase in the UV-Vis irradiation absorption. The best electrodes modified with WO3 to the both syntheses were applied in the photoelectrocatalytic oxidation (PEC) of bisphenol-A (BPA) and propylparaben (PPB) compounds, under UV-Vis irradiation. The PEC method presented an excellent performance in acidic conditions, applying a bias potential of +1.50 V and +0.50 V for Ti/TiO2-NT/WO3 and Ti/TiO2/WO3 electrodes, respectively. The mineralization of BPA and PPB compounds was greater than 80% for both Ti/TiO2-NT/WO3 and Ti/TiO2/WO3. In relation to the removal rate, BPA and PPB were completely removed after 45 and 60 min, respectively, for Ti/TiO2/WO3 electrodes and after 30 minutes for Ti/TiO2-NT/WO3 electrodes. Additionally, the electrodes presented a low energy consumption and good chemical stability. Compared to the photocatalysis (PC), the PEC was 2 times higher to the mineralization efficiency for Ti/TiO2-NT/WO3 and almost 20% higher for Ti/TiO2/WO3. Thus, the modifications of the TiO2 electrodes with WO3 represent an important contribution to the performance of materials and, therefore, a positive step for the application in alternative treatments of decontamination of wastewater. It was also of interest in this work to propose a new method for the insertion of nanotubes (TiNT) and nanosheets (TiNS) of titanates inside of TiO2 nanotubes via electrophoretic deposition. In this study was developed a simple and efficient method for the modification of complex nanostructures. The movement of the counter electrode on the surface of the working electrode, adapted with a brush on the edges, reduced the thickness of the TiNS/TiNT layer. The potential applied (20 V) and the mechanical stimulation in the surface were important for the incorporation of TiNS/TiNT into the pores of TiO2-NTs. As a result, the electrodes increased the hydrophobicity and an improvement to the direct oxidation capacity compared to the unmodified electrode.

Neste trabalho focou-se na preparação de materiais com aplicação em processos de tratamento de compostos orgânicos poluentes. Especificamente, buscou-se correlacionar as propriedades físicas e químicas dos materiais com as suas respostas catalíticas nos processos de fotocatálise heterogênea e de ozonização. Empregando-se o método de precipitação, preparou-se óxidos mistos de TiO2 e CeO2 em diferentes proporções. A caracterização destes materiais mostrou uma correlação entre a formação de partículas anisotrópicas, com morfologia do tipo bastão, e a capacidade de degradação de fenol pelo processo de fotocatálise heterogênea. Em particular, obteve-se 70% de degradação de fenol para o material com 20% CeO2. A interação entre o TiO2 e CeO2 também foi estudada em materiais preparados pelo método sol-gel. A presença do CeO2 retardou a transformação do polimorfo anatásio para rutilo, bem como manteve a estrutura de poros quando os matareriais foram calcinados a 650 ºC. Esta maior estabilidade possui relação com as propriedades fotocatalíticas dos materiais calcinados. Degradou-se 77% de fenol com o fotocatalisador 0,5% CeO2. Fotocatalisadores híbridos de SiMgOx e TiO2 foram preparados pela deposição de diferentes quantidades de TiO2 em placas de sepiolitas por slip-casting. Avaliou-se os materiais híbridos na degradação de ar contaminado com tricloroetileno (TCE) pelo processo de fotocatálise heterogênea. Observou-se uma dependência entre a espessura da camada de TiO2 e a taxa de degradação e mineralização do TCE, obtendo-se até 100% de degradação do TCE. Os materiais híbridos também tiveram suas propriedades catalíticas avaliadas na fotodegradação de TCE utilizando radiação solar. A combinação das propriedades de adsorção da sepiolita e fotocatalíticas do TiO2 possibilitaram 100% de degradação do TCE via incidência de radiação solar. O estudo de materiais híbridos também foi realizado com a preparação de esferas híbridas de carbono e CeO2. Este novo material foi preparado em uma única etapa, pelo método hidrotermal, sem a necessidade de emprego de solventes orgânicos. As esferas híbridas foram aplicadas na degradação de solução aquosa de ácido salicílico pelo processo de ozonização. As esferas eram, possívelmente, formadas por um core de carbono com nanopartículas de CeO2 dispersas em sua superfície hidrofílica. O efeito sinérgico entre a estrutura de carbono e o CeO2 resultou em um aumento de 25% na mineralização da solução de ácido salicílico pelo processo de ozonização. / This study was focused on the preparation of materials applied to the treatment of organic pollutant compounds. The main idea was to correlate the physical and chemical properties of these materials with their catalytic responses in heterogeneous photocatalysis and ozonation processes. Using the precipitation method, TiO2 and CeO2 mixed oxides were prepared in different proportions. The characterization of these materials showed a correlation between the formation of anisotropic rod-like particles and the capacity of degradation of phenol by a heterogeneous photocatalysis process. It was actived 70% of phenol degradation using the material with 20% CeO2. The interaction between TiO2 and CeO2 was also studied in materials prepared by the sol-gel method. The presence of CeO2 retarded the transition from anatase to rutile polymorphic, as well as maintained the porous structure when the materials were calcinated at 650 ºC. This major stability is related to the photocatalytic properties of the calcinated materials. For instance, 77% of the phenol was degraded using the 0.5% CeO2 photocatalyst. Hybrid photocatalysts composed by SiMgOx and TiO2 were prepared by depositing different amounts of TiO2 on sepiolite plates by slip-casting method. The performances of hybrid materials were evaluated by the degradation of contaminated air with trichloroethylene (TCE) using the heterogeneous photocatalysis process. A correlation between the thickness of the TiO2 layer and the degradation and mineralization rates of TCE was observed, obtaining up to 100% degradation of the TCE. Also, the catalytic properties of the hybrid materials were evaluated by TCE photodegration using solar radiation. A combination of the adsorption properites of the sepiolite and the photocatalytic properties of TiO2 allowed up to 100% of TCE degradation under incidence of solar radiation. The study of hybrid materials was also carried out with the preparation of carbon and CeO2 hybrid spheres. This novel material was prepared in one-pot step, using the hydrothermal method, without organic solvents. The hybrid spheres were used in the degradation of aqueous solution of salicylic acid by the ozonization process. The spheres were possibly formed by a core containing carbon with CeO2 nanoparticles dispersed on their hydrophilic surface.The synergetic effect between the carbon structure and the CeO2 resulted in an increase of 25% in the salicylic acid solution mineralization.

Tecnologias efetivas para o tratamento de águas e efluentes representam um dos grandes desafios da nossa sociedade; dentre as opções, a fotoeletrocatálise pode ser considerada como uma técnica alternativa e de interesse. Nesse contexto, o presente trabalho teve como objetivo desenvolver eletrodos de TiO2 modificados visando o tratamento fotoeletrocatalítico de interferentes endócrinos. Realizou-se inicialmente a síntese de nanotubos de TiO2 (TiO2-NT) sobre substrato de Ti metálico via anodização eletroquímica em eletrólito NaH2PO4/HF. Para minimizar as limitações inerentes ao TiO2 realizou-se a eletrodeposição de WO3 sobre os nanotubos de TiO2 (Ti/TiO2-NT/WO3) e diretamente sobre o substrato de Ti metálico. Este último revelou a formação de uma camada fina de TiO2 sobre a superfície, posterior ao tratamento térmico, formando um compósito (Ti/TiO2/WO3). A análise de difração de raios-X confirmou a formação da fase monoclínica de WO3 para ambas as sínteses e a fase anatase para os eletrodos de Ti/TiO2-NT/WO3. Para as duas sínteses, as medidas de energia dispersiva de raios-X revelaram uma quantidade crescente de W na composição dos eletrodos com o aumento do tempo de eletrodeposição. Teores elevados de W (acima de 1,2 %) apresentaram uma diminuição expressiva nos valores de fotocorrente. No entanto, baixos teores de W (entre 0,4 e 1,2 %) indicaram um aumento de 20 % nos valores de fotocorrente para os eletrodos de Ti/TiO2-NT/WO3 (20 mA cm-2) e Ti/TiO2/WO3 (17 mA cm-2) comparados aos não modificados, no potencial de +2,0 V. As análises de reflectância difusa mostraram uma baixa energia de bandgap (≈ 2,90 eV, eletrodos de Ti/TiO2-NT/WO3) e um aumento na absorção da irradiação UV-Vis. Posteriormente, os eletrodos modificados foram aplicados na oxidação fotoeletrocatalítica (FE) dos compostos bisfenol-A (BPA) e propilparabeno (PPB), sob irradiação UV-Vis. O método FE apresentou um excelente desempenho em condições ácidas, aplicando-se potencial de +1,50 V e +0,50 V para os eletrodos Ti/TiO2-NT/WO3 e Ti/TiO2/WO3, respectivamente. A mineralização dos compostos BPA e PPB foi superior a 80 % tanto para o Ti/TiO2-NT/WO3 como para o Ti/TiO2/WO3. Quanto à taxa de remoção, o BPA e PPB foram completamente removidos após 45 e 60 min, respectivamente, para os eletrodos de Ti/TiO2/WO3 e após 30 minutos para os eletrodos de Ti/TiO2-NT/WO3. Adicionalmente, os eletrodos apresentaram um baixo consumo energético e boa estabilidade química. Comparada à técnica de fotocatálise (FC), a FE revelou uma eficiência de mineralização 2 vezes superior para o Ti/TiO2-NT/WO3 e mais de 20 % superior para o Ti/TiO2/WO3. Logo, as modificações dos eletrodos de TiO2 com WO3 constituíram importantes contribuições para o desempenho dos materiais, sendo um passo importante para a aplicação em tratamentos alternativos de descontaminação de águas residuárias. Ainda foi de interesse neste trabalho propor um método para a inserção de nanotubos (TiNT) e nanofolhas (TiNS) de titanatos no interior de nanotubos de TiO2 via eletroforese. O estudo possibilitou o desenvolvimento de um método simples e eficiente para a modificação de nanoestruturas complexas. A movimentação do contra eletrodo sobre a superfície do eletrodo de trabalho, adaptado com uma escova nas laterais, reduziu a espessura da camada de TiNS/TiNT. O potencial aplicado (20 V) e a estimulação mecânica da superfície foram importantes para a incorporação das nanoestruturas dentro dos poros de TiO2-NTs. Como resultado, os eletrodos apresentaram um aumento da hidrofobicidade e uma melhora na capacidade de oxidação direta comparado ao eletrodo não modificado. / Effective technologies for the water and wastewater treatment represent a challenges for our society; among the options, the photoelectrocatalysis can be considered a promising and interesting alternative. In this context, the objective of this study was to develop modified TiO2 electrodes for the photoelectrocatalytic treatment of endocrine disruptors. The synthesis of TiO2 nanotubes (TiO2-NT) on metallic Ti substrate was carried out via electrochemical anodization in NaH2PO4 /HF electrolyte. In order to minimize the limitations inherent of TiO2, the electrodeposition of WO3 was performed on the TiO2 nanotubes (Ti/TiO2-NT/WO3) and also in the metallic Ti substrate. The deposition on the Ti metallic produced a thin layer of TiO2 on the surface, subsequent to the heat treatment, generating a composite (Ti/TiO2/WO3). The X-ray diffraction analysis (XRD) confirmed the monoclinic phase of WO3 for both the syntheses and the anatase phase of TiO2 for the Ti/TiO2-NT/WO3 electrodes. For the two syntheses, the X-ray dispersive energy (EDX) analisys indicated an increasing amount of tungsten (W) in the composition of the electrodes with increasing of electrodeposition time. High W content (above 1.2%) showed a significant decrease in the photocurrent values. However, low content of W (between 0.4 and 1.2 %) indicated an increase of 20 % in the photocurrent values for the electrodes Ti/TiO2-NT/WO3 (20 mA cm-2) and Ti/TiO2/WO3 (17 mA cm-2) compared to the unmodified ones, at the potential of +2.0 V. Difuse reflectance analysis indicated low bandgap energy (≈ 2.90 eV, Ti/TiO2-NT/WO3 electrodes) and an increase in the UV-Vis irradiation absorption. The best electrodes modified with WO3 to the both syntheses were applied in the photoelectrocatalytic oxidation (PEC) of bisphenol-A (BPA) and propylparaben (PPB) compounds, under UV-Vis irradiation. The PEC method presented an excellent performance in acidic conditions, applying a bias potential of +1.50 V and +0.50 V for Ti/TiO2-NT/WO3 and Ti/TiO2/WO3 electrodes, respectively. The mineralization of BPA and PPB compounds was greater than 80% for both Ti/TiO2-NT/WO3 and Ti/TiO2/WO3. In relation to the removal rate, BPA and PPB were completely removed after 45 and 60 min, respectively, for Ti/TiO2/WO3 electrodes and after 30 minutes for Ti/TiO2-NT/WO3 electrodes. Additionally, the electrodes presented a low energy consumption and good chemical stability. Compared to the photocatalysis (PC), the PEC was 2 times higher to the mineralization efficiency for Ti/TiO2-NT/WO3 and almost 20% higher for Ti/TiO2/WO3. Thus, the modifications of the TiO2 electrodes with WO3 represent an important contribution to the performance of materials and, therefore, a positive step for the application in alternative treatments of decontamination of wastewater. It was also of interest in this work to propose a new method for the insertion of nanotubes (TiNT) and nanosheets (TiNS) of titanates inside of TiO2 nanotubes via electrophoretic deposition. In this study was developed a simple and efficient method for the modification of complex nanostructures. The movement of the counter electrode on the surface of the working electrode, adapted with a brush on the edges, reduced the thickness of the TiNS/TiNT layer. The potential applied (20 V) and the mechanical stimulation in the surface were important for the incorporation of TiNS/TiNT into the pores of TiO2-NTs. As a result, the electrodes increased the hydrophobicity and an improvement to the direct oxidation capacity compared to the unmodified electrode.