Ces dernières années, les problèmes d’environnement et de dépollution sont devenus cruciaux. En particulier, les industries textiles sont une source très importante de pollution des milieux aquatiques. De 60 à 70 % des colorants de l’industrie textiles contiennent une ou plusieurs fonctions azoïques et sont pour la plupart d’entre eux toxiques, mutagènes et cancérigènes. L’objectif de la thèse a été d’évaluer l’efficacité du procédé photocatalytique pour éliminer des colorants anioniques et cationiques seuls ou en mélange en présence de dioxyde de titane et d’argile pontée au titane, synthétisé au laboratoire. Trois colorants sont étudiés comme modèle le bleu de Méthylène (BM), le noir Rémazol 5 (NR5) et le réactif rouge 2 (RR2). La première partie du travail est une étude cinétique de l’adsorption, de la dégradation et de la minéralisation de ces colorants à différents pH. Plusieurs conclusions émergent (1) l’isotherme d’adsorption n’est pas une isotherme de Langmuir (2) aucune corrélation n’est observée entre les quantités adsorbées et les vitesses de dégradation et (3) à forte concentration en colorants, une partie de la lumière est absorbée et la vitesse de dégradation diminue. La seconde partie du travail concerne l’étude du mélange des deux colorants anioniques. L’influence du rapport molaire, du pH et de la concentration initiale sur l’isotherme d’adsorption, la cinétique de décoloration et de minéralisation des deux colorants dans le mélange sont étudiés et comparés à celle obtenues pour les colorants pris individuellement. Aucun complexe n’est formé. Des compétitions entre les deux colorants sont observées après saturation de la surface de TiO2. Au-delà de la saturation du catalyseur un ralentissement de la minéralisation du COT et des hétéroatomes est observé. La troisième partie de l’étude est dédiée à l’étude de la préparation, caractérisation et propriétés photocatalytique de l’argile pontée au TiO2 (MMT-TiO2) et du matériau composite : argile pontée au TiO2 dopée avec de l’argent (MMT-TiO2/Ag). Cette étude est réalisée sur le colorant cationique (BM) et le colorant anionique (NR5). Une adsorption totale du colorant BM est observée, contrairement au NR5 qui ne s’adsorbe pratiquement pas, suggérant une adsorption par liaison ionique. L’argile pontée dopée ou non ne présente pas des propriétés photocatalytiques plus importantes que celle de TiO2 mais joue un rôle important sur l’adsorption des colorants cationiques, ce qui favorise leur élimination de la solution aqueuse. La présence d’Ag diminue les propriétés d’adsorption et de photocatalyse de l’argile pontée. / The problems of environment become crucial. In particular, textile industries are important sources of pollution of the aquatic system. 60% to 70% of dyes used in these textiles industries are azo dyes containing one or more; some of them are toxic, mutagenic and carcinogenic compounds. The aim was to evaluate the efficiency of photocatalytic processed for the elimination of anionic and cationic dyes alone or in combination with titanium dioxide and clay pillared with titanium, synthesized in the laboratory. The photocatalytic processing is interesting because solar flux can be used. Three dyes were studied as model: methylene blue (BM), black Remazol 5 (NR5) and reactive red 2 (RR2). The first part of this work is a kinetic study of adsorption, degradation and mineralization of these dyes at different pH. Several conclusions emerge (1) the adsorption isotherm is not of Langmuir type(2) no correlation exists between the quantities adsorbed and the degradation rates and (3) at high concentration, a part of UV is absorbed by the dye and the degradation rate decreases. The second part of the work involves the study of the mixture of two anionic dyes. The concentration of both dyes in the mixture, the influence of molar ratios, pH and initial concentration on the adsorption isotherm, kinetics of decolorization and mineralization of the two dyes in the mixture are compared to that obtained for the individual dyes. No complex is formed and competition between the two dyes occurs only after saturation of the photocatalyst surface. Beyond the saturation of the catalyst a slower mineralization of TOC and heteroatoms are observed. The third part deals with the preparation, characterization and photocatalytic properties of TiO2 pillared clay (MMT-TiO2) and of a composite material: TiO2 pillared clay doped with silver (MMT -TiO2/Ag), performed on the cationic dye (MB) and the anionic dye (NR5). A total adsorption of the BM dye is observed. Constrasting with the NR5 adsorption suggesting an adsorption by ionic bond. The pillared clay doped or not with silver but favors the elimination of dyes from the aqueous solution by adsorption. The presence of silver reduces the adsorption properties and photocatalysis properties of the pillared clay.

Disorders of the central nervous system (CNS) continuously pose problems for current therapeutics. In part, this is due to the uncertainty of underlying pathophysiological changes that give rise to specific disorders. Parkinson’s disease (PD) specifically is a neurodegenerative CNS disorder with unknown origins of dopaminergic degeneration in the substantia nigra. Current therapies are reactive in nature and no existing neuroprotective therapies are available. Two hypotheses have been proposed to contribute to dopaminergic degeneration in PD: endoplasmic reticulum (ER) stress and oxidative stress. This thesis investigates molecular targets involved in each of these responses (mesencephalic astrocyte-derived neurotrophic factor (MANF) and cyclin-dependent 5 (CDK5)/p25 respectively) to support a multi-hit hypothesis in PD neural degeneration. Using behavioural and biochemical analysis, a reduction in MANF was found to participate in the ER stress hypothesis and CDK5/p25 hyperactivation is a viable neuroprotective target related to the oxidative stress hypothesis. Both pathways are evidenced in PD pathology and this thesis proposes specific targets for both pathways in the development of necessary neuroprotective therapies. Subsequently, included in this thesis is a chapter about the unmet pharmacological alleviation of negative and cognitive symptom domains in another CNS disorder of unknown pathophysiology: schizophrenia (SZ). These untreated symptoms are thought to be caused by irregularities in the signalling of multiple neurotransmitter systems. This chapter investigates the role of synapsin II, a protein involved in regulating signalling of multiple neurotransmitters, in manifesting negative and cognitive SZ symptoms and analyzes brain glucose metabolism. Reduced synapsin II levels were consistently implicated in the underlying physiology, and therefore synapsin II is proposed as a potential pharmacological target for these unmedicated symptomologies. Overall this thesis uses interrelated studies to propose novel molecular targets to address unmet therapeutic needs based on evidence of their involvement in the pathophysiology of PD and SZ. / Thesis / Doctor of Philosophy (PhD) / Brain diseases like Parkinson’s disease (PD) and Schizophrenia (SZ) are difficult to treat because their cause has not been discovered. PD shows degeneration of cells in the brain but the cause for degeneration is unknown. This makes developing treatments to protect cells from dying difficult. Two pathways are suggested to cause cell death in PD. This thesis proposes that both pathways are responsible for degeneration through a combined effort. Here, both pathways are shown to lead to cell death resembling PD and specific molecules are suggested as targets for developing protective treatments. Like PD, SZ has symptoms that cannot be treated because the cause is unclear. A protein was investigated for producing SZ-like symptoms and found to have potential for treatment design. This thesis aims to understand molecular changes in the brain leading to PD, with a look at SZ and how they can be used for better treatment design.

CDK5 est une protéine kinase exprimée de façon ubiquitaire et activée principalement dans le système nerveux central, ou elle joue un rôle important dans la transmission synaptique, la guidance axonale et la migration cellulaire, la plasticité synaptique et le développement neuronal. CDK5 est associée à la protéine p35 au niveau de la membrane cellulaire, et activée par clivage calpaine-dépendant de cette dernière en p25, ce qui conduit à la relocalisation de CDK5/p25 dans le cytoplasme cellulaire. CDK5/p25 phosphoryle de nombreux substrats dont la protéine Tau, contribuant ainsi à l’apparition de plaques neurofibrillaires responsable des pathologies neurodégénératives comme Alzheimer et Parkinson, lorsqu’elle est hyperactivée. Plus récemment, l’expression et l’hyperactivation de CDK5 a été décrite comme impliquée dans le développement de cancers et en particulier de tumeurs cérébrales. Toutefois aucune approche ne permet actuellement de détecter et de mesurer l’activité de CDK5/p25 directement dans des cellules vivantes, au sein des tissus et des tumeurs concernées, dû à un manque d’outils fiables et sensibles pour quantifier les changements dynamiques de son activité kinase. Par ailleurs, peu d’inhibiteurs sont actuellement disponibles pour inhiber CDK5/p25, de manière spécifique, la plupart ciblant la poche de fixation de l’ATP.Le premier objectif de ma thèse a consisté à développer un biosenseur d’activité fluorescent de nature peptidique appelé CDKACT5 qui rapporte l’activité kinase de CDK5/p25 recombinante et dans des extraits cellulaires de manière dynamique et réversible suivant stimulation ou inhibition de cette kinase. Une fois caractérisé et validé in vitro, le biosenseur a été appliqué à la détection d’altérations de CDK5/p25 dans différentes lignées cellulaires de glioblastome dans des essais fluorescents d’activité kinase. Enfin CDKACT5 a été introduit dans des cellules neuronales vivantes afin de suivre les changements dynamiques d’activité de CDK5/p25 par microscopie de fluorescence et vidéo microscopie.Le deuxième objectif de ma thèse a consisté à développer un biosenseur fluorescent conformationnel dans le but d’identifier des inhibiteurs non compétitifs de l’ATP ciblant la boucle d’activation de CDK5. Le biosenseur CDKCONF5 a été exploité pour réaliser un criblage haut débit de trois chimiothèques de petites molécules. Les touches identifiées ont été validées et caractérisées in vitro, pour déterminer leur potentiel inhibiteur dans des tests d’activité kinase et de prolifération cellulaire, ainsi que leur mécanisme d’action. Ces molécules constituent des candidats prometteurs pour une chimiothérapie sélective du glioblastome. / CDK5 is a protein kinase ubiquitously expressed but mainly activated in the central nervous system, where it plays an important role in neuronal functions such as synaptic transmission, axonal guidance and migration, synaptic plasticity and neuronal development. CDK5 is associated with p35 protein at the cell membrane, then activated by calpain-mediated cleavage of p35 into p25, which promotes relocalization of CDK5/p25 into the cytoplasm. CDK5/p25 phosphorylates a wide variety of substrates including Tau, thereby contributing to appearance of neurofibrillary plaques responsable for neurodegenerative pathologies such as comme Alzheimer’s et Parkinson’s, when hyperactivated. More recent studies suggest that CDK5 expression and hyperactivation are involved in glioblastoma during cell invasion and CDK5 expression has been reported to be correlated with the pathological grade of gliomas. However there are currently no tools available to monitor CDK5/p25 activity in its native cellular environment, in tissues or in tumours, due to an overall lack of reliable tools to quantify dynamic changes in its kinase activity in a sensitive and continuous fashion. Furthermore, few inhibitors are currently available to target CDK5/p25 in a specific fashion and most of them are ATP competitive inhibitors.The first goal of my thesis was to develop a fluorescent peptide biosensor named CDKACT5, that specifically reports on recombinant CDK5/p25 and on endogenous CDK5 activity in cell extracts in a dynamic and reversible fashion following stimulation or inhibition of this kinase. Once validated in vitro, this biosensor was applied to detect alterations in CDK5/p25 activity in different glioblastoma cell lines in fluorescent kinase activity assays. Finally CDKACT5 was introduced into cultured neuronal cells to monitor dynamic changes in CDK5/p25 activity by fluorescence imaging and time-lapse microscopy.The second goal of my thesis project consisted in developing a conformational fluorescent biosensor to identify non-ATP competitive inhibitors targeting the activation loop of CDK5. CDKCONF5 was implemented to perform a high throughput screen of three small molecule libraries. The hits identified were validated and characterized to determine their inhibitory potential in kinase activity and proliferation assays, as well as their mechanism of action. These compounds constitute promising for selective chemotherapy in glioblastoma.

O demorado tratamento térmico, comum no preparo de fotocatalisadores e sua imobilização em substratos, foi contornado nesta tese, em que se investigaram duas estratégias de modificação de eletrodos de ouro com TiO2 P25. A primeira consiste em promover a formação de uma nanocamada pela simples exposição do metal por 1 min à suspensão aquosa de TiO2 (10 g L-1 em HCl 0,1 mol L-1); na segunda, deposita-se uma pequena alíquota (5 ou 8 µL) da suspensão diretamente no substrato (drop coating) para secá-lo em seguida por irradiação com lâmpada incandescente (60 W a 20 cm), obtendo-se bons resultados de uma a três camadas depositadas. Comprovou-se grande aumento da estabilidade da suspensão aquosa e duplicação da atividade fotocatalítica do nanofilme de TiO2 em decorrência da repulverização de P25 comercial em almofariz, melhoria inalcançável por sonicação da suspensão. O tamanho de partícula médio obtido por DLS para o TiO2 disperso em meio de HCl 0,1 mol L-1 atingiu 103±3 nm, enquanto que o filme depositado na superfície do ouro (observado por MEV e caracterizado por EDS) não ultrapassou 100 nm de espessura, sendo dominado por partículas de diâmetro de 20 (anatase) a 30 nm (rutilo), observadas por MET. A estabilidade da suspensão é susceptível ao ânion do ácido utilizado, sendo que resultados igualmente satisfatórios foram obtidos com HCl e HclO4 0,1 mol L-1, enquanto que para a mesma concentração de H2SO4 o TiO2 sofreu sedimentação rápida e o eletrodo preparado com a suspensão apresentou fotoatividade 10x menor. Filmes de espessuras bastante distintas (100 nm e 2 m) depositados a partir de suspensão 10 g L-1 por contato e drop coating com gota de 5,0 µL, respectivamente, foram comparados em relação à sua capacidade de transporte de elétrons e resposta eletroquímica ao Fe(CN)6 3 1,0 mmol L-1, sendo que a carga líquida formal de oxidação do EDTA 1,0 mmol L-1 é apenas 50 % maior para o filme 20x mais espesso, além de gerar distorções consideráveis nas ondas voltamétricas do sistema-sonda reversível em relação ao filme nanométrico e à superfície polida. Com eletrodos modificados pelo protocolo otimizado de drop coating (8,0 µL de TiO2 2 g L-1), testou-se o efeito da presença de diferentes eletrólitos de suporte (ácidos 0,1 mol L-1) em processos anódicos de fotooxidação em geral. A curva de decaimento da fotocorrente iph com o tempo pode ser descrita por uma equação de decaimento exponencial duplo iph = i0 + A1 exp(k1t) + A2 exp( k21t), permitindo distinguir as contribuições da fotocorrente de oxidação da água (i0) e de termos referentes a dois tipos de sítio superficiais, sendo um de cinética rápida e outro de cinética lenta. A seguinte ordem foi determinada para a fotocorrente total inicial (iph0 total) dos eletrólitos: HNO3 > HClO4 > HCl > H1SO4 > H3PO4 e as explicações propostas para tal se embasam na adsortividade dos ânions no TiO2 e na reatividade dos respectivos traps formados. O mesmo modelo de ajuste matemático foi utilizado para avaliar a fotoatividade do eletrodo modificado pela sua irradiação sucessiva e repetida em HNO3 0,1 mol L-1 (sem EDTA), sendo observada redução significativa principalmente nos parâmetros relativos aos sítios de reação e, assim, sugere-se um impedimento dos mesmos através, p. ex., da formação de peróxidos superficiais. Na presença também de EDTA, a carga líquida total despendida na sua fotooxidação se mantém relativamente constante nas sucessivas irradiações. Por fim, os experimentos de fotooxidação do EDTA sob varredura de potencial revelaram uma região de relação linear entre a fotocorrente e o potencial aplicado ao eletrodo modificado com TiO2 que se estende até a região de saturação de fotocorrente ser atingida, comportamento compatível com filmes nanoparticulados porosos não-dopados. A inclinação da região linear aumenta em função da [EDTA], como se os valores de condutância (di/dE) se elevassem dependendo da reação interfacial. Ajuste de modelo matemático hiperbólico correlacionando a (foto)resistência do filme em função da fotocorrente de saturação R = R0 + kIsph1, fornece resistência ôhmica do filme R0 de 5,0 kΩ e uma constante atrelada ao fotopotencial de 237 mA Ω. Já a curva monotônica de fotocorrente de saturação (Isph) com a [EDTA] apresenta comportamento linear até cerca de 0,7 mmol L-1, sugerindo-se que nessa região o controle por transporte de massa é a etapa limitante do processo global. Acima dessa concentração o coeficiente angular diminui gradualmente à medida que a reação de cinética de captura das lacunas passa a ser o determinante até um limite máximo (aparentemente 5,0 mmol L-1 de EDTA, nas condições do experimento) onde a disponibilidade de lacunas fotogeradas passa a governar. / The lengthy thermal treatment is a common step during the preparation and immobilization of photocatalysers on substrates, which by the way, was overcome in this thesis by the investigation of two strategies of modification of gold electrodes with P25 TiO2. The first one consists in promoting the formation of a nanolayer by the simple exposure of the metal surface to an aqueous suspension of TiO2 (10 g L-1 on 0.1 mol L-1 HCl) during 1 min; the second involves the deposition of a small drop (5 or 8 L) of the suspension on the gold substrate (drop coating) and its drying by irradiation with an incandescent lamp (60 W at 20 cm far), with worthy results also for two or three deposited layers. The stability of this aqueous suspension was appreciably improved by the repulverization of commercial P25 in a grinding mortar. As a consequence the photocatalytic activity conferred to the electrode by the formation of the TiO2 nanofilm doubled. Such improvements cannot be attained by bath sonication of the suspension. The average particle size determined by DLS for the TiO2 dispersed in 0.1 mol L-1 HCl was 103±3 nm, while the film deposited on the surface of gold consisted of particles of 20 nmn (anatase) and 30 nm (rutile) characterized by TEM and barely achieved a thickness of 100 nm (characterized by SEM and EDS). The stability of the modifying suspension is susceptible to the type of anion of the electrolyte. Good results were found with 0.1 mol L-1 HCl and HClO4, but not with 0.1 mol L-1 H2SO4. This last medium causes fast sedimentation of TiO2 and generates electrodes with one tenth of the photoactivity achieved with the other acids. The effect of film thickness on the photoactivity was evaluated for films with 100 nm and 2.0 µm prepared from a 10 g L-1 TiO2 suspension by the contact and drop coating (5 µL) strategies, respectively. The electron transport across both films and the electrochemical response for the 1.0 mmol L-1 Fe(CN) 63- probe was compared. The formal net charge for the 1.0 mmol L-1 EDTA oxidation was only 50 % higher for the 20x thicker film that also considerably distorts the voltammetric waves of the aforementioned reversible probe. The effect of different supporting electrolytes (0.1 mol L-1 acids) on the anodic photooxidation processes in general was tested with electrodes modified by an optimized drop coating protocol (8.0 µL of 2 µg L-1 TiO2). The curve describing the photocurrent decay in function of time might be ascribed to an equation of double exponential decay iph = i0 + A1 exp(k1t) + A2 exp (k2t), which allows the distinction of the contribution of water oxidation (i0) from terms of two types of surface sites: a kinetically fast site and a slow one. The total initial photocurrent (iph0 total) of the following electrolytes decays in the order: HNO3 > HClO4 > HCl > H2SO4 > H3PO4; explanations comprise the adsorbability of each respective anion on TiO2 and the reactivity of the corresponding traps formed. Similar curve fitting applied to the data of photoactivity of the gold electrode during successive irradiations of its surface in 0.1 mol L-1 HNO3 (absence of EDTA) revealed that sites reactivities underwent considerable reduction. It is suggested that during repetitive experiments the sites are impaired by the formation of surface peroxides. However, in the presence of 1.0 mmol L-1 of EDTA, the formal net charge of oxidation of the organic species remains almost unaltered. Ultimately, the experiments concerning the photooxidation of EDTA under linear potential scan revealed a region of linear relation between the photocurrent and the potential applied to the electrode modified with a TiO2 film (nanometric or micrometric), which holds until the saturation photocurrent is attained. This behavior is typical for porous non-doped nanoparticulate electrodes. The slope of the linear region increase somewhat with the EDTA concentration, as though the conductance values (di/dE) were raised depending on the interfacial reaction rate. The fitting of a hyperbolic model R = R0 + kIsph-1 for the correlation of the (photo)resistence (R) of the film with the photocurrent of saturation (Isph) allows the estimation of an ohmic resistance of 5.0 kΩ, and a photopotential related constant of 237 mA Ω. The curve of correlation between Isph and the [EDTA] is linear fit until 0.7 mmol L-1, suggesting that in this initial region the mass transport to the interface is the limiting step of the global process. Above that concentration, the slope of the curve is gradually reduced as the kinetic of capture of the holes becomes the determining step and from 5.0 mmol L-1 on an asymptotic Isph is reached (under the conditions of the experiments), where the holes photogeneration might start governing.

A atrazina (ATZ) é um herbicida utilizado em larga escala no Brasil de forma intensiva em culturas de cana-de-açúcar, milho e sorgo. A ATZ possui caráter persistente e recalcitrante, de forma que os tratamentos convencionais de efluentes não são capazes de removê-lo. Nesse contexto, os processos oxidativos avançados, como a fotocatálise heterogênea, têm se mostrado eficientes para remoção deste poluente. Este trabalho tem por objetivo avaliar o desempenho dos fotocatalisadores TiO2 P25 e C-TiO2 Kronos vlp 7000 modificado com carbono para a degradação do pesticida atrazina em solução aquosa, utilizando um reator fotoquímico com coletor parabólico composto irradiado por um simulador solar. Os catalisadores TiO2 P25 e C-TiO2 Kronos foram caracterizados por meio de difração de raios-X, espectroscopia de infravermelho, área superficial específica BET e análise de reflectância difusa. As concentrações de TiO2 P25 e C-TiO2 Kronos empregadas foram 500 e 100 mg L&-1, respectivamente. Os resultados obtidos mostraram significativa remoção de ATZ ao final de 120 minutos (100; 98; 98; 93; 86% para concentrações iniciais de ATZ de 1; 5; 10; 20 e 30 mg L-1, respectivamente) com emprego do catalisador TiO2 P25. No entanto, as análises de carbono orgânico total (COT) indicaram que não houve mineralização significativa da ATZ, com valores inferiores a 20% com o uso do TiO2 P25. Para o catalisador C-TiO2 Kronos não se obteve remoção importante da ATZ ao final de 120 minutos de experimento, quando comparado com o TiO2 P25. Neste caso, o catalisador C-TiO2 Kronos permitiu obter remoções do pesticida de 37; 35; 38; 39 e 45%, aproximadamente, para as concentrações iniciais de ATZ de 1; 5; 10; 20 e 30 mg L-1, respectivamente. Apesar disso, o catalisador C-TiO2 Kronos apresentou melhor desempenho em mineralizar a ATZ a CO2 e H2O em relação ao proporcionado pelo TiO2 P25, com aproximadamente 38% de mineralização. O modelo de Langmuir-Hinshelwood (LH) constitui uma aproximação adequada para a cinética de degradação da atrazina para ambos os catalisadores estudados, com valores de Kr e Kads iguais a 1,54 mg L-1 min-1 e 15,47 L mg-1, respectivamente, para o catalisador TiO2 P25 e de 1,34 mg L-1 min-1 e 132,95 L mg-1, respectivamente para o catalisador C-TiO2 Kronos vlp 7000. / Atrazine (ATZ) is a widely used herbicide in Brazil, where it is intensively applied in sugarcane, corn and sorghum cultivations. However, conventional wastewater treatments are not able to remove ATZ due to its persistent and recalcitrant properties. Advanced oxidation processes, such as heterogeneous photocatalysis, have been proved effective for the removal of this pollutant. This study aims to evaluate the performance of TiO2 P25 and carbon-modified TiO2 Kronos vlp 7000 photocatalysts in the degradation of ATZ in aqueous systems using a tubular photochemical reactor equipped with a compound parabolic collector (CPC) irradiated by simulated solar light. Catalysts TiO2 P25 and C-TiO2 Kronos were characterized by X-ray diffraction, infrared spectroscopy, BET analysis and diffuse reflectance analysis. The concentrations of TiO2 P25 and C-TiO2 Kronos were 500 and 100 mg L-1, respectively. For TiO2 P25, the results showed significant ATZ removals after 120 minutes of irradiation (100; 98; 98; 93; 86% for initial ATZ concentrations of 1; 5; 10; 20, and 30 mg L-1, respectively). In contrast, the total organic carbon (TOC) analyses indicated that no significant ATZ mineralization occurred, with values lower than 20% for TiO2 P25. In comparison with TiO2 P25, C-TiO2 was not able to completely remove ATZ at the end of 120 minutes of irradition. In this case, pesticide removals of about 37; 35; 38; 39 and 45% were obtained for initial ATZ concentrations of 1; 5; 10; 20, and 30 mg L-1, respectively. Nevertheless, C-TiO2 Kronos showed better performance for ATZ mineralization to CO2 and H2O in comparison with TiO2 P25, with approximately 38% total carbon organic removal. The Langmuir-Hinshelwood (LH) model was shown to be an appropriate approximation for the degradation kinetics of atrazine for both catalysts, with values of Kr and Kads equal to 1.54 mg L-1 min-1 and 15.47 mg L-1, respectively, for the P25 TiO2 and 1.34 mg L-1 min-1 and 132.95 mg L-1, respectively, for C-TiO2 Kronos vlp 7000.

A atrazina (ATZ) é um herbicida utilizado em larga escala no Brasil de forma intensiva em culturas de cana-de-açúcar, milho e sorgo. A ATZ possui caráter persistente e recalcitrante, de forma que os tratamentos convencionais de efluentes não são capazes de removê-lo. Nesse contexto, os processos oxidativos avançados, como a fotocatálise heterogênea, têm se mostrado eficientes para remoção deste poluente. Este trabalho tem por objetivo avaliar o desempenho dos fotocatalisadores TiO2 P25 e C-TiO2 Kronos vlp 7000 modificado com carbono para a degradação do pesticida atrazina em solução aquosa, utilizando um reator fotoquímico com coletor parabólico composto irradiado por um simulador solar. Os catalisadores TiO2 P25 e C-TiO2 Kronos foram caracterizados por meio de difração de raios-X, espectroscopia de infravermelho, área superficial específica BET e análise de reflectância difusa. As concentrações de TiO2 P25 e C-TiO2 Kronos empregadas foram 500 e 100 mg L&-1, respectivamente. Os resultados obtidos mostraram significativa remoção de ATZ ao final de 120 minutos (100; 98; 98; 93; 86% para concentrações iniciais de ATZ de 1; 5; 10; 20 e 30 mg L-1, respectivamente) com emprego do catalisador TiO2 P25. No entanto, as análises de carbono orgânico total (COT) indicaram que não houve mineralização significativa da ATZ, com valores inferiores a 20% com o uso do TiO2 P25. Para o catalisador C-TiO2 Kronos não se obteve remoção importante da ATZ ao final de 120 minutos de experimento, quando comparado com o TiO2 P25. Neste caso, o catalisador C-TiO2 Kronos permitiu obter remoções do pesticida de 37; 35; 38; 39 e 45%, aproximadamente, para as concentrações iniciais de ATZ de 1; 5; 10; 20 e 30 mg L-1, respectivamente. Apesar disso, o catalisador C-TiO2 Kronos apresentou melhor desempenho em mineralizar a ATZ a CO2 e H2O em relação ao proporcionado pelo TiO2 P25, com aproximadamente 38% de mineralização. O modelo de Langmuir-Hinshelwood (LH) constitui uma aproximação adequada para a cinética de degradação da atrazina para ambos os catalisadores estudados, com valores de Kr e Kads iguais a 1,54 mg L-1 min-1 e 15,47 L mg-1, respectivamente, para o catalisador TiO2 P25 e de 1,34 mg L-1 min-1 e 132,95 L mg-1, respectivamente para o catalisador C-TiO2 Kronos vlp 7000. / Atrazine (ATZ) is a widely used herbicide in Brazil, where it is intensively applied in sugarcane, corn and sorghum cultivations. However, conventional wastewater treatments are not able to remove ATZ due to its persistent and recalcitrant properties. Advanced oxidation processes, such as heterogeneous photocatalysis, have been proved effective for the removal of this pollutant. This study aims to evaluate the performance of TiO2 P25 and carbon-modified TiO2 Kronos vlp 7000 photocatalysts in the degradation of ATZ in aqueous systems using a tubular photochemical reactor equipped with a compound parabolic collector (CPC) irradiated by simulated solar light. Catalysts TiO2 P25 and C-TiO2 Kronos were characterized by X-ray diffraction, infrared spectroscopy, BET analysis and diffuse reflectance analysis. The concentrations of TiO2 P25 and C-TiO2 Kronos were 500 and 100 mg L-1, respectively. For TiO2 P25, the results showed significant ATZ removals after 120 minutes of irradiation (100; 98; 98; 93; 86% for initial ATZ concentrations of 1; 5; 10; 20, and 30 mg L-1, respectively). In contrast, the total organic carbon (TOC) analyses indicated that no significant ATZ mineralization occurred, with values lower than 20% for TiO2 P25. In comparison with TiO2 P25, C-TiO2 was not able to completely remove ATZ at the end of 120 minutes of irradition. In this case, pesticide removals of about 37; 35; 38; 39 and 45% were obtained for initial ATZ concentrations of 1; 5; 10; 20, and 30 mg L-1, respectively. Nevertheless, C-TiO2 Kronos showed better performance for ATZ mineralization to CO2 and H2O in comparison with TiO2 P25, with approximately 38% total carbon organic removal. The Langmuir-Hinshelwood (LH) model was shown to be an appropriate approximation for the degradation kinetics of atrazine for both catalysts, with values of Kr and Kads equal to 1.54 mg L-1 min-1 and 15.47 mg L-1, respectively, for the P25 TiO2 and 1.34 mg L-1 min-1 and 132.95 mg L-1, respectively, for C-TiO2 Kronos vlp 7000.

O demorado tratamento térmico, comum no preparo de fotocatalisadores e sua imobilização em substratos, foi contornado nesta tese, em que se investigaram duas estratégias de modificação de eletrodos de ouro com TiO2 P25. A primeira consiste em promover a formação de uma nanocamada pela simples exposição do metal por 1 min à suspensão aquosa de TiO2 (10 g L-1 em HCl 0,1 mol L-1); na segunda, deposita-se uma pequena alíquota (5 ou 8 µL) da suspensão diretamente no substrato (drop coating) para secá-lo em seguida por irradiação com lâmpada incandescente (60 W a 20 cm), obtendo-se bons resultados de uma a três camadas depositadas. Comprovou-se grande aumento da estabilidade da suspensão aquosa e duplicação da atividade fotocatalítica do nanofilme de TiO2 em decorrência da repulverização de P25 comercial em almofariz, melhoria inalcançável por sonicação da suspensão. O tamanho de partícula médio obtido por DLS para o TiO2 disperso em meio de HCl 0,1 mol L-1 atingiu 103±3 nm, enquanto que o filme depositado na superfície do ouro (observado por MEV e caracterizado por EDS) não ultrapassou 100 nm de espessura, sendo dominado por partículas de diâmetro de 20 (anatase) a 30 nm (rutilo), observadas por MET. A estabilidade da suspensão é susceptível ao ânion do ácido utilizado, sendo que resultados igualmente satisfatórios foram obtidos com HCl e HclO4 0,1 mol L-1, enquanto que para a mesma concentração de H2SO4 o TiO2 sofreu sedimentação rápida e o eletrodo preparado com a suspensão apresentou fotoatividade 10x menor. Filmes de espessuras bastante distintas (100 nm e 2 m) depositados a partir de suspensão 10 g L-1 por contato e drop coating com gota de 5,0 µL, respectivamente, foram comparados em relação à sua capacidade de transporte de elétrons e resposta eletroquímica ao Fe(CN)6 3 1,0 mmol L-1, sendo que a carga líquida formal de oxidação do EDTA 1,0 mmol L-1 é apenas 50 % maior para o filme 20x mais espesso, além de gerar distorções consideráveis nas ondas voltamétricas do sistema-sonda reversível em relação ao filme nanométrico e à superfície polida. Com eletrodos modificados pelo protocolo otimizado de drop coating (8,0 µL de TiO2 2 g L-1), testou-se o efeito da presença de diferentes eletrólitos de suporte (ácidos 0,1 mol L-1) em processos anódicos de fotooxidação em geral. A curva de decaimento da fotocorrente iph com o tempo pode ser descrita por uma equação de decaimento exponencial duplo iph = i0 + A1 exp(k1t) + A2 exp( k21t), permitindo distinguir as contribuições da fotocorrente de oxidação da água (i0) e de termos referentes a dois tipos de sítio superficiais, sendo um de cinética rápida e outro de cinética lenta. A seguinte ordem foi determinada para a fotocorrente total inicial (iph0 total) dos eletrólitos: HNO3 > HClO4 > HCl > H1SO4 > H3PO4 e as explicações propostas para tal se embasam na adsortividade dos ânions no TiO2 e na reatividade dos respectivos traps formados. O mesmo modelo de ajuste matemático foi utilizado para avaliar a fotoatividade do eletrodo modificado pela sua irradiação sucessiva e repetida em HNO3 0,1 mol L-1 (sem EDTA), sendo observada redução significativa principalmente nos parâmetros relativos aos sítios de reação e, assim, sugere-se um impedimento dos mesmos através, p. ex., da formação de peróxidos superficiais. Na presença também de EDTA, a carga líquida total despendida na sua fotooxidação se mantém relativamente constante nas sucessivas irradiações. Por fim, os experimentos de fotooxidação do EDTA sob varredura de potencial revelaram uma região de relação linear entre a fotocorrente e o potencial aplicado ao eletrodo modificado com TiO2 que se estende até a região de saturação de fotocorrente ser atingida, comportamento compatível com filmes nanoparticulados porosos não-dopados. A inclinação da região linear aumenta em função da [EDTA], como se os valores de condutância (di/dE) se elevassem dependendo da reação interfacial. Ajuste de modelo matemático hiperbólico correlacionando a (foto)resistência do filme em função da fotocorrente de saturação R = R0 + kIsph1, fornece resistência ôhmica do filme R0 de 5,0 kΩ e uma constante atrelada ao fotopotencial de 237 mA Ω. Já a curva monotônica de fotocorrente de saturação (Isph) com a [EDTA] apresenta comportamento linear até cerca de 0,7 mmol L-1, sugerindo-se que nessa região o controle por transporte de massa é a etapa limitante do processo global. Acima dessa concentração o coeficiente angular diminui gradualmente à medida que a reação de cinética de captura das lacunas passa a ser o determinante até um limite máximo (aparentemente 5,0 mmol L-1 de EDTA, nas condições do experimento) onde a disponibilidade de lacunas fotogeradas passa a governar. / The lengthy thermal treatment is a common step during the preparation and immobilization of photocatalysers on substrates, which by the way, was overcome in this thesis by the investigation of two strategies of modification of gold electrodes with P25 TiO2. The first one consists in promoting the formation of a nanolayer by the simple exposure of the metal surface to an aqueous suspension of TiO2 (10 g L-1 on 0.1 mol L-1 HCl) during 1 min; the second involves the deposition of a small drop (5 or 8 L) of the suspension on the gold substrate (drop coating) and its drying by irradiation with an incandescent lamp (60 W at 20 cm far), with worthy results also for two or three deposited layers. The stability of this aqueous suspension was appreciably improved by the repulverization of commercial P25 in a grinding mortar. As a consequence the photocatalytic activity conferred to the electrode by the formation of the TiO2 nanofilm doubled. Such improvements cannot be attained by bath sonication of the suspension. The average particle size determined by DLS for the TiO2 dispersed in 0.1 mol L-1 HCl was 103±3 nm, while the film deposited on the surface of gold consisted of particles of 20 nmn (anatase) and 30 nm (rutile) characterized by TEM and barely achieved a thickness of 100 nm (characterized by SEM and EDS). The stability of the modifying suspension is susceptible to the type of anion of the electrolyte. Good results were found with 0.1 mol L-1 HCl and HClO4, but not with 0.1 mol L-1 H2SO4. This last medium causes fast sedimentation of TiO2 and generates electrodes with one tenth of the photoactivity achieved with the other acids. The effect of film thickness on the photoactivity was evaluated for films with 100 nm and 2.0 µm prepared from a 10 g L-1 TiO2 suspension by the contact and drop coating (5 µL) strategies, respectively. The electron transport across both films and the electrochemical response for the 1.0 mmol L-1 Fe(CN) 63- probe was compared. The formal net charge for the 1.0 mmol L-1 EDTA oxidation was only 50 % higher for the 20x thicker film that also considerably distorts the voltammetric waves of the aforementioned reversible probe. The effect of different supporting electrolytes (0.1 mol L-1 acids) on the anodic photooxidation processes in general was tested with electrodes modified by an optimized drop coating protocol (8.0 µL of 2 µg L-1 TiO2). The curve describing the photocurrent decay in function of time might be ascribed to an equation of double exponential decay iph = i0 + A1 exp(k1t) + A2 exp (k2t), which allows the distinction of the contribution of water oxidation (i0) from terms of two types of surface sites: a kinetically fast site and a slow one. The total initial photocurrent (iph0 total) of the following electrolytes decays in the order: HNO3 > HClO4 > HCl > H2SO4 > H3PO4; explanations comprise the adsorbability of each respective anion on TiO2 and the reactivity of the corresponding traps formed. Similar curve fitting applied to the data of photoactivity of the gold electrode during successive irradiations of its surface in 0.1 mol L-1 HNO3 (absence of EDTA) revealed that sites reactivities underwent considerable reduction. It is suggested that during repetitive experiments the sites are impaired by the formation of surface peroxides. However, in the presence of 1.0 mmol L-1 of EDTA, the formal net charge of oxidation of the organic species remains almost unaltered. Ultimately, the experiments concerning the photooxidation of EDTA under linear potential scan revealed a region of linear relation between the photocurrent and the potential applied to the electrode modified with a TiO2 film (nanometric or micrometric), which holds until the saturation photocurrent is attained. This behavior is typical for porous non-doped nanoparticulate electrodes. The slope of the linear region increase somewhat with the EDTA concentration, as though the conductance values (di/dE) were raised depending on the interfacial reaction rate. The fitting of a hyperbolic model R = R0 + kIsph-1 for the correlation of the (photo)resistence (R) of the film with the photocurrent of saturation (Isph) allows the estimation of an ohmic resistance of 5.0 kΩ, and a photopotential related constant of 237 mA Ω. The curve of correlation between Isph and the [EDTA] is linear fit until 0.7 mmol L-1, suggesting that in this initial region the mass transport to the interface is the limiting step of the global process. Above that concentration, the slope of the curve is gradually reduced as the kinetic of capture of the holes becomes the determining step and from 5.0 mmol L-1 on an asymptotic Isph is reached (under the conditions of the experiments), where the holes photogeneration might start governing.

[pt] A busca pela diminuição da dependência de combustíveis fósseis faz com que a ciência avance, diariamente, na utilização de combustíveis ecológicos, como o H2. Uma das formas de sua obtenção é através da fotocatálise. Esse processo consiste em uma reação catalítica com o uso de energia, na forma de luz. A fotólise da água é amplamente utilizada, principalmente com luz solar como fonte luminosa, que é abundante e reduz os custos de sua produção. O desempenho desta reação depende da posição das bandas de condução (BC) e valência (BV) do fotocatalisador. O TiO2 é utilizado como fotocatalisador em diversas reações, inclusive para a produção de H2. Os fotocatalisadores utilizados na forma de pós nanométricos apresentam dificuldade de separação após a reação. A transformação do pó em um material compacto é uma alternativa para retirá-lo do meio reacional evitando perdas e custos com separação. Desse modo, a compactação do pó é uma alternativa para facilitar sua reciclagem. O principal método de sua produção é pelo processo de sinterização, que envolve temperaturas elevadas (geralmente, 75 por cento do ponto de fusão do material) e longo tempo, podendo durar até dias. Para diminuir os gastos energéticos, o processo de sinterização a frio é uma opção, que consiste na densificação do material com uso de pressão e um solvente (aquoso ou não) e, temperaturas de sinterização de até 500 Graus C. O objetivo do estudo consistiu na produção de pastilhas de TiO2, comercial, e P25, através de uma variação do método de sinterização a frio, onde aplicou-se a pressão no pó, junto com o solvente, antes de seu tratamento térmico. As pastilhas produzidas foram caracterizadas pelas técnicas de TGA/DSC, XRD, MEV, CV, e DRS. / [en] The quest to reduce dependence on fossil fuels makes science advance, daily, in the use of ecological fuels, such as H2. One of the ways to obtain it is through photocatalysis. This process consists on a catalytic reaction using energy, in the form of light. Water photolysis is widely used, mainly with sunlight as a light source, which is abundant and reduces production costs. The performance of this reaction depends on the position of the conduction (CB) and valence (VB) bands of the photocatalyst. TiO2 is used as a photocatalyst in several reactions, including the production of H2. Photocatalysts used in the form of nanometric powders have difficulty in separating after the reaction. The transformation of the powder into a compact material is an alternative to remove it from the reaction medium, avoiding losses and costs with separation. Thus, the compaction of the powder is an alternative to facilitate its recycling. The main method of its production is through the sintering process, which involves high temperatures (generally 75 percent of the material s melting point) and a long time, which can last up to days. To reduce energy costs, the cold sintering process is an option, which consists of densifying the material using pressure and a solvent (aqueous or not) and sintering temperatures of up to 500 C degrees. The aim of the study was the production of commercial TiO2 and P25 pellets, through a variant of the cold sintering method, where pressure was applied to the powder, with the proper solvent, before the heat treatment. The pellets produced were characterized by the techniques of TGA/DSC, XRD, SEM, CV, and DRS.

In this paper we analyse regional growth in Central and Eastern Europe in the second half of the 1990s, a period in which pronounced disparities between a group of catching-up regions and another group of falling back regions appeared. We aim to identify the factors behind a dynamic growth performance and the weaknesses leading to poor growth and thus investigate the role of (foreign) investment, education and innovation as well as geographical factors in a model of economic growth. The key relationships proposed by this model are then estimated with empirical data for the period 1995-2000 using spatial econometric tools. We find that foreign direct investment was paramount for regional growth in that period. EU border regions and capital areas clearly outperformed others. Further, regional growth clusters have appeared. Surprisingly, the high level of secondary education in Eastern European regions played no role with growth. Higher education, in contrast served to facilitate technology transfer. (author's abstract) / Series: EI Working Papers / Europainstitut

<p>Ispitana je direktna i indirektna razgradnja odabranih&nbsp; &beta;-blokatora (metoprolol- tartarata, MET i propranolol-hidrohlorida, PRO) kao i diuretika (hidrohlortiazida, HCTZ) i njegovog stabilnog intermedijera hidrolize 4-amino-6-hlor-1,3-benzendisulfonamida (ABSA). Praćena je i kinetika razgradnje direktnom i indirektnom fotolizom uz primenu UVA, UVC, sunčevog i simuliranog sunčevog zračenja (SSZ). Najpre je ispitana&nbsp; stabilnost MET pod dejstvom SSZ, UVA, UVC, UVA/H₂O_{2 ,} i UVA/&nbsp; BrO₃^-. Dalje je ispitana efikasnost razgradnje MET pod dejstvom O₃i UVC/O_3. Identifikovano je deset intermedijera tokom UVC, O_3&nbsp;i UVC/O₃ razgradnje, pri&nbsp; čemu samo jedan ima značajno vi&scaron;u toksičnost prema algama i bakterijama u odnosu na ostale. Efikasnost fotokatalitičke razgradnje MET je ispitana u TiO₂ suspenzijama sa komercijalnim katalizatorima (Wackherr i Degussa P25). Mehanizam fotokatalitičke razgradnje je detaljno ispitan, pri&nbsp; čemu je identifikovano&nbsp; četrnaest intermedijera. EC₅₀ vrednost MET i njegovih sme&scaron;a nastalih pri fotokatalitičkoj razgradnji su određene na tri ćelijske linije sisara (H-4-II-E, HT-29 i MRC-5). Kako bi se povećala efikasnost&nbsp; rocesa fotokatalitičke razgradnje primenom komercijalnih katalizatora, ispitan je&nbsp; uticaj prisustva elektron-akceptora u suspenziji, pri čemu je upoređen uticaj O₂/H₂O₂, i O₂/ BrO₃^-&nbsp;na mehanizam razgradnje. Na osnovu teorije funkcionala gustine stekao se uvid u promene unutar molekula MET u prisustvu reaktivnih radikala. Takođe, ispitana je efikasnost nedopiranih TiO₂ , kao i dopiranih La(III) nanoprahova sintetisanih sol&minus;gel postupkom, u razgradnji MET. Uticaj temperature &nbsp;kalcinacije na fotokatalitičku efikasnost TiO 2 nanoprahova dopiranih pomoću La(III) &nbsp;ispitana je na supstratima MET i PRO, pri čemu je analiziran i uticaj strukture&nbsp; polaznog jedinjenja na&nbsp; informacija efikasnost fotokatalitičke razgradnje. Rezultati su upoređeni sa nedopiranim TiO₂nanoprahom i TiO₂Degussa P25 (pri pH-vrednosti 9). Pored toga, ispitana je kinetika i toksičnost PRO i njegovih intermedijera nastalih tokom razgradnje sa TiO₂Degussa P25. Ispitan je i uticaj strukture polaznog jedinjenja (MET, HCTZ i ABSA) na fotorazgradnju pod dejstvom&nbsp;UVA, sunčevog i simuliranog sunčevog zračenja, u odsustvu/prisustvu TiO₂ Degussa P25. Takođe, ispitan je i sinergistički efekat MET i ABSA na proces hidrolize, direktne fotolize i fotokatalize sa SSZ/TiO₂Degussa P25. Kako bi se stekao uvid u toksičnost proučavanih sistema, ispitan je njihov uticaj na rast odabranih ćelijskih linija sisara.</p> / <p>Direct and indirect degradation of selected&nbsp; &beta;-blockers (metoprolol tartrate, MET and&nbsp;propranolol hydrochloride, PRO) and also diuretic (hydrochlorothiazide, HCTZ) in &nbsp;addition to its stable hydrolysis intermediate 4-amino-6-chloro-&nbsp;&nbsp; 1,3-benzenedisulfonamide (ABSA) were investigated. The kinetics of their degradation obtained by direct and indirect photolysis under UVA, UVC, sunlight and simulated sunlight irradiation (SSI) have been followed. Firstly, the stability of MET under influence of SSI, UVA, UVC, UVA/H₂O₂ , and UVA/&nbsp; BrO₃^- has been investigated. Further, the efficiency of MET degradation under influence of O₃, and UVC/O₃ has been explored. Ten intermediates have been identified during the UVC, O₃, and UVC/O₃ treatments, while only one intermediate had significantly higher toxicity towards the algae and bacteria in respect to the others. Efficiency of&nbsp; photocatalytic degradation of MET was investigated in TiO₂ suspensions with&nbsp;commercial catalysts (Wackherr and Degussa P25). Mechanism of photocatalytic degradation was investigated in detail according to which fourteen intermediates were identified. EC 50 &nbsp;value of MET and its mixtures formed during the photocatalytic degradation has been determined at three mammalian cell lines (H-4-II-E, HT-29, and MRC-5). In order to improve the efficiency of photocatalytic degradation process applying commercial catalysts, the influence of presence of electron acceptors in suspension has been investigated and the influence of O₂/H₂O_2&nbsp;and O₂/BrO₃^- to the mechanism of degradation has been compared. Based on the density&nbsp; functional theory an insight to the changes within MET molecule in the presence of reactive radicals has been made. Also, the efficiency of bare TiO₂, as well as&nbsp;doped La(III) nanopowders synthesized by sol-gel procedure, in the degradation of&nbsp; MET has been investigated. The influence of calcination temperature on&nbsp; hotocatalytic efficiency of TiO_2&nbsp;nanopowders doped with La(III) has been studied on the MET and&nbsp; PRO substrates, and the influence of structure of the starting compound on the&nbsp; efficiency of &nbsp;photocatalytic degradation had been analyzed. Results have been&nbsp; compared with bare TiO_2&nbsp;nanopowder and TiO₂ Degussa P25 (at pH value of 9). Besides, kinetics and toxicity of PRO and its intermediates formed during the degradation with TiO₂ Degussa P25 have been investigated. The influences of starting compound&rsquo;s structure (MET, HCTZ, and ABSA) to photodegradation under UVA, sunlight and SSI, in the absence/presence of TiO₂ Degussa P25, have been investigated. Also, the synergistic effects of MET and ABSA to the process of&nbsp; hydrolysis, direct photolysis, and photocatalysis with SSI/TiO₂ Degussa P25 have been investigated. In order to get &nbsp;an insight into the toxicity of the studied systems, their influence on the growth of selected mammalian cell lines has been investigated as well.</p>