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[ES] La demanda de agua y la contaminación del agua son dos problemas ligados no solo de los últimos años sino también para el futuro. Mucho se ha hecho en el pasado para eliminar los contaminantes emergentes (CEC) de los sistemas acuáticos, utilizando diferentes tipos de técnicas; entre ellos, los mediados por luz han obtenido gran atención en los últimos años, debido a su alta eficiencia y sus bajos costos. Entre todas estas técnicas, se han desarrollado Procesos Avanzados de Oxidación y Reducción (AOPs y ARPs, respectivamente) para eliminar eficientemente las CECs. En detalle, en esta tesis se ha investigado el uso de moléculas orgánicas como fotocatalizadores en combinación con luz solar y visible; La riboflavina y la eosina Y han sido seleccionadas como fotocatalizadores por sus diferentes propiedades químicas: la primera es una molécula natural, conocida por sus propiedades oxidativas, mientras que la segunda es un colorante sintético. El objetivo principal de esta tesis doctoral fue investigar la degradación de varias clases de CEC mediante el uso de fotocatalizadores orgánicos y luz visible. En detalle, se monitorearon las tendencias de degradación de cada CEC frente al tiempo en diferentes condiciones de trabajo, con el fin de encontrar el mejor sistema de fotodegradación. Además, se investigó el mecanismo de funcionamiento mediante la determinación de los principales fotoproductos y mediante el estudio de las especies reactivas generadas, involucradas en los procesos. Se realizaron pruebas de toxicidad adicionales para tener una visión general de todos los participantes del sistema. Al final, toda la información se combinó para postular un mecanismo de degradación hipotético para todos los CEC. Más concretamente, la tesis se podría dividir en dos partes principales: en los capítulos 3 y 4 se llevó a cabo la oxidación de CECs, mientras que en los capítulos 5 y 6 se evaluaron las condiciones reductoras. En detalle, en los capítulos 3 y 4, se oxidaron tres compuestos farmacéuticos en presencia de riboflavina acetilada (RFTA) y luz visible. Específicamente, se investigaron carbamazepina, atenolol y noscapina en condiciones oxidativas. Los estudios de fotodegradación de los compuestos iniciales y de sus fotoproductos fueron importantes para comprender su oxidación natural en los sistemas acuosos naturales. Todas las vías oxidativas se consideraron en un mecanismo de degradación hipotético final. Además, en los capítulos 5 y 6, se investigó la fotodegradación de algunos ejemplos de estabilizadores UV de benzotriazol (BUVS). Los BUVS son compuestos muy recalcitrantes, que no se ven afectados en condiciones oxidativas. En consecuencia, se probaron múltiples sistemas fotocatalíticos y, finalmente, varios BUVS se degradaron en condiciones reductoras en presencia de RFTA o eosina Y (EOY) como fotocatalizadores, un donante de sacrificio como DABCO y luz visible. Al igual que en los capítulos anteriores, las mediciones fotoquímicas fueron necesarias para determinar la principal ruta de degradación y las especies químicas reactivas involucradas en el proceso. Se han realizado experimentos adicionales en presencia de otros donantes de sacrificio y agua marina para recrear un entorno natural real para estudios futuros. / [CA] La demanda d'aigua i la contaminació de l'aigua són dos problemes lligats no sols dels últims anys sinó també per al futur. Molt s'ha fet en el passat per a eliminar els contaminants emergents (CECs) dels sistemes aquàtics, utilitzant diferents tipus de tècniques; entre ells, els mediats per llum han obtingut gran atenció en els últims anys, a causa de la seua alta eficiència i els seus baixos costos. Entre totes aquestes tècniques, s'han desenvolupat Processos Avançats d'Oxidació i Reducció (AOPs i ARPs, respectivament) per a eliminar eficientment les CECs. Detalladament, en aquesta tesi s'ha investigat l'ús de molècules orgàniques com fotocatalizadores en combinació amb llum solar i visible; la riboflavina i l'eosina I han sigut seleccionades com fotocatalizadores per les seues diferents propietats químiques: la primera és una molècula natural, coneguda per les seues propietats oxidatives, mentre que la segona és un colorant sintètic. Detalladament, es van monitorar les tendències de degradació de cada CEC enfront del temps en diferents condicions de treball, amb la finalitat de trobar el millor sistema de fotodegradación. A més, es va investigar el mecanisme de funcionament mitjançant la determinació dels principals fotoproductos i mitjançant l'estudi de les espècies reactives generades, involucrades en els processos. Es van realitzar proves de toxicitat addicionals per a tindre una visió general de tots els participants del sistema. Al final, tota la informació es va combinar per a postular un mecanisme de degradació hipotètic per a tots els CEC. Més concretament, la tesi es podria dividir en dues parts principals: en els capítols 3 i 4 es va dur a terme l'oxidació de CECs, mentre que en els capítols 5 i 6 es van avaluar les condicions reductores. Detalladament, en els capítols 3 i 4, es van oxidar tres compostos farmacèutics en presència de riboflavina acetilada (RFTA) i llum visible. Específicament, es van investigar carbamazepina, atenolol i noscapina en condicions oxidatives. Els estudis de fotodegradación dels compostos inicials i dels seus fotoproductos van ser importants per a comprendre la seua oxidació natural en els sistemes aquosos naturals. Totes les vies oxidatives es van considerar en un mecanisme de degradació hipotètic final. A més, en els capítols 5 i 6, es va investigar la fotodegradación d'alguns exemples d'estabilitzadors UV de benzotriazol (BUVS). Els BUVS són compostos molt recalcitrants, que no es veuen afectats en condicions oxidatives. En conseqüència, es van provar múltiples sistemes fotocatalíticos i, finalment, diversos BUVS es van degradar en condicions reductores en presència de RFTA o eosina I (EOY) com fotocatalizadores, un donant de sacrifici com DABCO i llum visible. Igual que en els capítols anteriors, els mesuraments fotoquímics van ser necessàries per a determinar la principal ruta de degradació i les espècies químiques reactives involucrades en el procés. S'han realitzat experiments addicionals en presència d'altres donants de sacrifici i aigua marina per a recrear un entorn natural real per a estudis futurs. / [EN] Water request and water pollution are two bonded problems not only of the last years but also for the future. A lot has been done in the past in order to eliminate contaminants of emerging concerned (CECs) from the aquatic systems, using different kind of techniques; among them, those mediated by light have obtained great attention in the last years, due to their high efficiency and their low costs. Among all these techniques, Advanced Oxidation and Reduction Processes (AOPs and ARPs, respectively) have been developed in order to efficiently remove CECs. In detail, in this thesis the use of organic molecules as photocatalysts has been investigated in combination with solar and visible light; riboflavin and eosin Y have been selected as photocatalysts for their different chemical properties: the first is a natural molecule, well-known for its oxidative properties, while the second one is a synthetic dye. The main aim of this doctoral thesis was to investigate the degradation of various classes of CECs through the use of organic photocatalysts and visible light. In detail, degradation trends of each CEC was monitored vs time under different working conditions, in order to find the best photodegradation system. Moreover, the operating mechanism was investigated through the determination of the main photoproducts and through the study of the generated reactive species, involved in the processes. Additional toxicity tests were performed in order to have an overall view of all the participants of the system. At the end, all the information was combined to postulate an hypothetical degradation mechanism for all the CECs. More specifically, the thesis could be divided in two main parts: in chapters 3 and 4 oxidation of CECs was carried out, while in chapters 5 and 6 reductive conditions were evaluated. In detail, in chapters 3 and 4, three pharmaceutical compounds were oxidized in the presence of acetylated riboflavin (RFTA) and visible light. Specifically, carbamazepine, atenolol and noscapine were investigated under oxidative conditions. Photodegradation studies of the initial compounds and of their photoproducts were important in order to understand their natural oxidation in the natural aqueous systems. All the oxidative pathways were considered in a final hypothetical degradation mechanism. Moreover, in chapters 5 and 6, the photodegradation of a few examples of the benzotriazole UV-stabilizers (BUVSs) was investigated. BUVSs are very recalcitrant compounds, not affected under oxidative conditions. Consequentially, multiple photocatalytic systems were tested and finally, various BUVSs were degraded under reductive conditions in the presence of RFTA or eosin Y (EOY) as photocatalysts, a sacrificial donor as DABCO and visible light. As in the previous chapters, photochemical measurements were necessary to determine the main degradation pathway and the reactive chemical species involved in the process. Additional experiments in the presence of other sacrificial donors and marine water have been performed in order to recreate a real natural environment for future studies. / Pavanello, A. (2022). Novel Mechanistic Insights on the Photoredox Degradation of CECs Using Organic Photocatalysts [Tesis doctoral]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/191002

In this project the photodegradation of 3,5-diamino-6-chloro-N-(2-(methylamino)ethyl)pyrazine-2-carboxamide was studied. A hypothetical degradation pattern for the compound was proposed and the aim of the project was to study the formed secondary photodegradants and to, if possible, structure elucidate some of these compounds. In order to do this, the parent compound was photodegraded in two steps, where a primary photodegradant was isolated using semi-preparative supercritical fluid chromatography (SFC) and then further degraded into the secondary photodegradants. The photodegradation was first carried out in aqueous solution, where the parent compound was irradiated in UV-A light of 300-400 nm. This resulted in a primary photodegradant with a molecular ion of m/z = 227, where the chloride in position 6 of the pyrazine group had been replaced by a hydroxyl group. During the large scale photodegradation, prior to the preparative purification, the yield of primary photodegradant was very low due to the photodegradation being dependent on both sample volume and concentration and due to the primary photodegradant also being unstable in aqueous solution at room temperature. Due to the above mentioned difficulties the parent compound was photodegraded in methanol instead of water in order to avoid the freeze-drying process where a lot of the primary photodegradant was lost. This resulted in a primary photodegradant with a molecular ion of m/z = 241, where the chloride had been replaced by a methoxy group instead of a hydroxyl group. This compound was more stable which allowed workup by rotary evaporation, instead of freeze-drying, before the preparative purification. This primary photodegradant was isolated using semi-preparative SFC on a Viridis® BEH Prep OBD TM column (250 x 30 mm, 5 µm) and a Luna HILIC column (250 x 30 mm, 5 µm) with MeOH/NH3 100/1 v/v as organic modifier. About 1.2 mg material was isolated and further photodegradation tests in ordinary water and 18O-water were conducted. Some secondary photodegradants were observed in LC-MS analyses, and their element compositions were proposed by accurate mass results. Fundamental structures for these compounds were proposed. Further structural investigational analyses are needed for confirmation in the future.

A lercanidipina (LER) é uma dihidropiridina bloqueadora de canais de cálcio disponível comercialmente como uma mistura racêmica, ou seja, uma mistura equimolar dos enantiômeros (R)-LER e (S)-LER. Os efeitos farmacológicos da LER residem essencialmente no enantiômero (S)-LER, e estudos in vitro mostram que este enantiômero apresenta cerca de 100-200 vezes maior afinidade pelos canais de cálcio que o enantiômero (R)-LER. Consequentemente, os efeitos farmacodinâmicos da LER são devidos, principalmente, ao enantiômero (S)-LER. Neste sentido, fármacos racêmicos são exaustivamente estudados, para avaliar suas propriedades farmacocinéticas e farmacodinâmicas estereosseletivas e verificar se existem vantagens na produção do enantiômero puro. Além disso, devido às diferenças na atividade dos enantiômeros, é imprescindível realizar o controle de qualidade enantiosseletivo destas formulações. Associado a isto, as moléculas pertencentes a esta classe de fármacos são fotossensíveis. Assim, o objetivo deste trabalho foi desenvolver e validar um método enantiosseletivo para análise da LER e aplicá-lo no controle de qualidade de formas farmacêuticas e também avaliar sua fotodegradação. A análise enantiosseletiva da LER e aplicação no controle de qualidade de formas sólidas foi realizado por eletroforese capilar (CE) utilizando tampão acetato de sódio 200 mmol L-1, pH 4,0 como eletrólito de corrida, adicionado de TM-?-CD (2, 3, 6-O-metil-?-ciclodextrina) 10 mmol L-1 como seletor quiral, na temperatura de 15 °C e 25 kV de tensão. Os parâmetros de desempenho analítico, linearidade, precisão, exatidão, limite de quantificação e detecção, seletividade e robustez foram avaliados e estão de acordo com os requisitos preconizados pelos guias oficiais. O método foi aplicado para análise de comprimidos comerciais contendo LER, e mostrou ser adequado para quantificação das amostras, apresentando valores de coeficiente de variação (CV, %) e erro relativo (E, %) inferiores a 5 %. Além disso, foi avaliada a fotoestabilidade dos enantiômeros da LER na mistura racêmica e também dos enantiômeros separados, quando expostos à luz UVC (254 nm) e visível, por HPLC. A separação dos enantiômeros da LER foi alcançada empregando a coluna quiral Chiralpak® AD 250 × 4,6 mm, partículas de 10 ?m e fase móvel composta por hexano-etanol-dietilamina (97:3:0,3, v/v/v) e vazão de 1,0 mL min-1. O método foi validado e aplicado nos estudos de fotodegradação em soluçãos-padrão de LER. Em relação à exposição na luz UVC (254 nm) e visível foi observada degradação significativa dos enantiômeros da LER após 0,5 h de exposição. Além disso, os produtos de degradação foram caracterizados por LC/MS/MS e foi observada que a principal fragmentação ocorre no anel dihidropiridínico, assim como para outros fármacos desta classe, formando piridinas sem efeitos farmacológicos. / Lercanidipine (LER) is a dihydropyridine calcium channel blocker commercially available as a racemic mixture, or an equimolar mixture of enantiomers (R) and LER (S)-LER. The pharmacological effects of LER essentially reside in the enantiomer (S)-LER, and in vitro studies show that this enantiomer has about 100-200 times greater affinity for calcium channels that the enantiomer (R)-LER. Consequently, the pharmacodynamic effects of LER are due mainly to the enantiomer (S)-LER. Thus, racemic drugs are extensively studied to evaluate their pharmacokinetic and pharmacodynamic properties stereoselective and check if there are advantages in the production of pure enantiomer. Moreover, due to differences in the activity of the enantiomers is essential to perform quality control enantioselective these formulations. Additonally, the molecules of this class of drugs are photosensitive. The objective of this study was to develop and validate a method for enantioselective analysis of LER and apply it in the quality control of pharmaceutical forms and also evaluate their photodegradation. The enantioselective analysis of LER and application in quality control of solid forms was performed by capillary electrophoresis (CE) using sodium acetate buffer 200 mmol L-1, pH 4.0 as background electrolyte, 10 mmol L-1TM-?-CD (2, 3, 6-O-methyl-?-cyclodextrin) as chiral selector, at temperature of 15 °C and 25 kV voltage. The analytical parameters, linearity, precision, accuracy, limit of quantification and detection, selectivity and robustness were evaluated and accordance with the requirements recommended by official guideline. The method was applied for the analysis of commercial tablets containing LER, and proved to be suitable for quantification of the samples, with of CV (%) and E (%) less than 5%. In addition, the photostability was evaluated on the LER enantiomers and racemic mixture of the enantiomers also separated when exposed to UVC (254 nm) and visible light by HPLC. Separation of enantiomers of LER was achieved using the chiral column Chiralpak ® AD 250 × 4.6 mm, particles of 10 micrometres and a mobile phase composed of hexane-ethanol-diethylamine (97:3:0.3 v/v/v ) and flow rate of 1.0 mL min-1. The method was validated and applied in studies of photodegradation of standard solutions of LER. The method was validated and applied in studies of photodegradation in soluçãos standard of LERR With relation to UVC exposure (254 nm) and visible light, significant degradation was observed after 0.5 hour exposure of the solution containing the racemic mixture and after 1 h of exposure the solution containing the isolated enantiomers of LER. Also, the degradation products were characterized by LC/MS/MS and it was observed that the major fragmentation occurs in dihydropyridine ring, as well as other drugs of this class, forming pyridines no pharmacological effects.

Efluentes contendo resíduos perigosos ou substâncias orgânicas recalcitrantes são geradas em uma ampla variedade de processos industriais. O manejo inadequado destes efluentes pode causar contaminação das águas superficiais e subterrâneas. O seu tratamento por processos convencionais muitas vezes não é eficiente, por vezes impedindo o despejo ou reutilização de águas em unidades industriais. Os processos oxidativos avançados têm sido o foco de vários estudos em busca de alternativas viáveis para o tratamento de águas residuais contendo contaminantes orgânicos tóxicos, ou recalcitrantes. No presente estudo, o processo foto-Fenton é abordado, com a utilização de luz solar como fonte de fótons. O estudo consistiu de uma etapa de experimentos em um reator solar provido de coletores parabólicos compostos (CPC), ligados a um tanque agitado equipado com lâmpadas elétricas. Este sistema de operação foi utilizado em diferentes configurações, como operação em batelada ou contínuo, com variação de área irradiada por luz solar e com variação da potência total das lâmpadas no tanque. Na maior parte dos experimentos, com o reator operando em regime batelada, mais de 90% do carbono orgânico dissolvido (COD) foi removido em menos de 3 horas de irradiação solar, um desempenho equivalente ao de reatores baseados em fontes de luz artificial. Os dados experimentais foram usados no ajuste de modelos matemáticos empíricos baseados em redes neurais para simulação da taxa de remoção de COD em função das condições experimentais. Este modelo foi combinado com balanços de massa, que permite simular o desempenho do reator para diferentes valores das variáveis operacionais e de projeto. Os resultados das simulações do modelo mostraram boa concordância com os dados experimentais para a maioria dos casos. Além de evidenciar a relação entre as variáveis de processo, os resultados obtidos possibilitam identificar aspectos importantes no projeto de reatores baseados em radiação solar para tratamento de efluentes. / Wastewaters containing hazardous, or recalcitrant organic substances are generated in a wide variety of industrial processes. The inadequate management of these effluents can cause contamination of underground and surface water. Their treatment by conventional processes may not be technically efficient, and usually prevents effluents from being discarded or reused in industrial processing units. Photochemical advanced oxidation technologies can be a feasible alternative for wastewater treatment. In this study the photo-irradiated Fenton process is considered, with the aim of utilizing solar radiation as a photon source to the process. The study comprised experiments carried out in a solar reactor based on compound parabolic collectors (CPC) connected to a stirred tank equipped with electric lamps. This reaction system operated under different conditions, and different configurations (continuous and batch operation, different solar irradiated area, different electric power for the light sources in the stirred tank). In general, the performance of the solar reactor was similar to the performance of reactors based on electric light sources (for instance, in batch operation more than 90% of the dissolved organic carbon in solution (DOC) was removed in less than 3 hours). The experimental results were used to fit a neural network-based mathematical model to simulate the DOC removal rate as a function of the experimental conditions. This model was combined with mass balances, enabling to simulate the reactor performance for different values of the operating and design variables. The model results showed good agreement with most of the experiments. The simulation results enabled to evaluate the effect of the variables included in the study, and to identify important aspects related to reactor performance under different conditions of solar radiation and electric energy sources.

The solar radiation in general and UV radiation in particular has been recognized to stimulate plant litter decomposition through photochemical mineralization of photosensitive organic molecules, such as lignin, facilitating microbial decomposition, with great relevance role in dryland ecosystems where microbial activity is low, however little is known about how photodegradation could influence other ecosystems without moisture limitations and under what conditions may be favored, therefore the mechanisms has not yet been established. Decomposition in tropical ecosystem is a complex process and can be induced by a number of environmental factors with certain differences when compared to arid and semi-arid ecosystems. To assess the mechanisms underlying UV-B photodegradation, we designed a 300 days field experiment at a tropical ecosystem with high levels of annual precipitation and exposure litter to three levels of radiation combined with a biocide treatment. Results show that the removal of UV-B radiation decelerated plant litter decomposition during the later stage compared to litter exposure to full sun, however shaded litter had similar mass loss compared to litter exposed to full sun. Furthermore, differences in the decay constant among radiation treatments due to UV-B effect is independent of lignin loss. Overall, our study suggest that UV-B contributes to the plant litter decomposition through carbon losses, however, had no effect on nitrogen, neither lignin nor cellulose loss. However, more studies are needed in order to investigate the positive and negative effects of UV exposure on microbial activity in tropical ecosystems. / A radiação solar em geral e a radiação ultravioleta (UV) em particular têm sido reconhecida por estimular a decomposição da serapilheira através da mineralização fotoquímica de moléculas fotossensíveis, como a lignina, facilitando a decomposição microbiana, com um papel de grande relevância em ecossistemas áridos onde a atividade microbiana é baixa, no entanto pouco se sabe como a fotodegradação pode influenciar outros ecossistemas como por exemplo os mais úmidos e sob quais condições a fotodegradação é favorecida, portanto os mecanismos ainda não foram estabelecidos. Decomposição em ecossistemas tropicais é um processo complexo e pode ser influenciado por vários fatores ambientais e com certas diferenças quando comparada com ecossistemas áridos e semiáridos. Para avaliar os mecanismos subjacentes à fotodegradação via radiação UV-B, um experimento de campo de 300 dias foi estabelecido em um ecossistema tropical com alto índice de precipitação anual onde a serapilheira foi exposta a três níveis de radiações diferentes, combinada com um tratamento com biocida. Resultados mostram que a remoção da radiação UV-B desacelerou a decomposição da serapilheira durante o último estágio do experimento comparado com a serapilheira exposta a radiação ambiente, no entanto a serapilheira quando sombreada teve perda de massa similar à exposta a radiação ambiente. Além disso, diferenças na taxa de decaimento entre os tratamentos de radiação devido ao efeito da radiação UV-B foram independentes da perda de lignina. No geral, nosso estudo sugere que a radiação UV-B contribui com a decomposição da serapilheira através da perda de carbono, no entanto não teve efeito na perda de massa de nitrogênio, lignina e celulose. Portanto, mais estudos são necessários para investigar o efeito positivo e negativo da exposição à radiação UV-B na atividade microbiana e na decomposição da serapilheira em ecossistemas tropicais.

Maintaining a constant supply of clean drinking water is among the most pressing global challenges in our time. About one-third of the population is affected by the water scarcity and it can only get worse with climate change, rapid industrialization, and the population growth. Even though nearly 70 percent of the planet is covered by water, the consumable freshwater content is only 2.5 percent of it. Unfortunately, the accessible portion of it is only 1 percent. Even so, most of the freshwater bodies are choked with pollution. Considering the vast availability of saline water on the planet and the increasing wastewater generation, seawater desalination, and wastewater treatment and recycling seem to have the potential to address current water-related issues. Therefore, it is necessary to find efficient techniques for seawater desalination and wastewater treatment. The use of nanostructured materials for these applications is becoming a popular approach due to the unique chemical and physical properties they possess compared to bulk materials Solar energy is the cleanest and most abundant renewable natural resource available. Materials for solar photothermal energy conversion are highly sought after for their cost savings, clean environment, and broad utility in providing water heating and/or steam for many applications including domestic water heating and solar-driven desalination. Extensive research efforts have been made to develop efficient solar absorbers with characteristics such as low weight, low thermal conductivity, broad solar absorption and porosity to be able to float on water to provide more efficient and cost-effective solar steam generation systems. Metal NPs have been proposed to take advantage of the high efficiency of the photothermal energy conversion associated with surface plasmon resonance absorption. Nanostructured carbon-based materials such as graphene oxide, carbon nanotubes, carbonized biomass are also in use due to their excellent photothermal energy conversion ability over the range of the visible and near infra-red region of the electromagnetic spectrum. In this dissertation, five projects based on the utility of nanostructured materials for desalination, photocatalysis and water treatment will be discussed. The first three projects involve the fabrication and design of plasmonic and carbon-based photothermal materials for applications in solar steam generation, water desalination, and wastewater treatment. In the fourth project, a unique shape of ZnO nanostructure was synthesized for photodegradation of organic dyes in industrial wastewater. The final project demonstrates the shape-controlled synthesis of iron carbide nanostructures and composite materials of aminated graphene oxide for the removal of Cr(VI) from wastewater.

Certains pesticides présentent une très bonne activité biologique en serre, lorsqu’ils sont protégés du rayonnement UV, mais pas en champs lorsqu’ils sont exposés à la totalité de la lumière solaire. Une dégradation photochimique par le rayonnement UV est alors suspectée. C’est le cas de la famille de fongicides contenant un groupement oxime dont nous avons étudié en détail la photodégradation d’un point de vue expérimental et théorique. La cinétique de phototransformation de ces fongicides a été mesurée en solution et en phase solide et les photoproduits de réaction ont été identifiés et quantifiés. L’ensemble des résultats nous a alors permis de proposer un mécanisme de photodégradation. Ces fongicides subissent à la fois une photoisomérisation et une photodégradation par rupture homolytique de la liaison oxime. Le rôle de certains éléments structuraux dans ces transformations a pu être établi grâce à plusieurs analogues. Une étude de modélisation moléculaire menée en parallèle a permis de déterminer la nature des voies réactionnelles mises en jeu après l’excitation de la molécule et ainsi d’expliquer les observations expérimentales. Ce travail avait pour objectif d’améliorer la photostabilité de cette famille de fongicides par des modifications structurales tout en respectant l’activité biologique par ailleurs tout à fait remarquable de ces composés. Le remplacement de l’oxime par un oxétane préparé par une réaction de Paternò-Büchi a été envisagé. / Some pesticides present a great biological activity in green house, while they are protected from UV radiations, but not in the field, while they are exposed to the whole spectrum of solar light. A photochemical degradation by UV light is then suspected. That is the case of the group of fungicides which contain an oxim moiety and that we studied the photodegradation in detail, both from experimental and theoretical points of view. The kinetics of phototransformation of these fungicides have been mesured in solution and in the solid phase and photoproducts have been identified and quantified. These results allowed us to propose a mecanism of photodegradation. These fungicides undergo simultanously a photoisomerisation and a photodegradation by a homolytic cleavage of the oxim bond. The role of some structural elements in these transformations has been set up thanks to several analogues. A parallel study of molecular modelisation allowed the determination of the nature of reactive paths followed after the excitation of the molecule and therefore the explanation of experimental observations. The objective of this work was to improve the photostability of this group of fungicides by structural modifications while keeping the remarquable biological activity of these compounds. The replacement of the oxim moiety by an oxetane prepared by a Paternò-Büchi reaction has been considered.

Made available in DSpace on 2015-05-14T13:21:21Z (GMT). No. of bitstreams: 1 ArquivoTotal.pdf: 4033083 bytes, checksum: 6a05100e863d9679efe9792a62865701 (MD5) Previous issue date: 2013-08-22 / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior - CAPES / The present work consists in two steps the synthesis of TiO2 nanoparticles and its evaluation in the photodegradation of textile dyes. The first step involves the synthesis of TiO2 by the microwave assisted solvothermal method, using templates in order to obtain new properties for the materials, due to changes in the surface area, morphology variations and control of the crystalline phase. An usual way to produce these materials is by the use of surfactants and polymers. In the present work, four templates were used, polyethylene glycol (PEG 2000), sodium dodecyl sulfate (SDS), cetiltrimetylamonium bromate (CTAB) and carboxymethylcelulose (CMC). Synthesis were done using na ethanolic route with titanium isopropoxide (1 mol/L), containing the templates or not. Solutions were solvothermalized in the microwave reactor for different times of synthesis (1, 30 and 60 min), in order to evaluate the behavior of the material with different periods of irradiation. Materials with high surface areas and different morphologies were obtained with average particle sizes in the range of 10-30 nm. Powders were characterized by X-ray diffraction (XRD), BET surface area, infrared spectroscopy (IR), Raman spectroscopy, ultraviolet-visible spectroscopy (UV-vis) and field emission scanning electronic microscopy (FE-SEM). The second step consists in the application of the photocatalysts in the photodegradation of the remazol golden yellow dye (RNL), when the photocatalytic efficiency of the TiO2 was observed with a meaningful influence of the properties as surface area and morphology in the photodegradation activity, with about 81 % of discoloration using TiCMC. Reactions were done using a photoreactor at room temperature, with periods of 1, 2 and 4 h with characterization of the azo dye by UV-vis spectroscopy. Photodegradation efficiency was compared to the TiO2 made by Degussa, the P25 one. / O presente trabalho consiste em duas etapas a síntese de nanopartículas de TiO2 e a sua avaliação na fotodegradação de corantes têxteis. A primeira etapa envolve a síntese dos fotocatalisadores de TiO2 pelo método solvotermal assistido por micro-ondas utilizando direcionadores com o intuito de promover novas propriedades nos materiais, acarretando em mudanças na área superficial, variações morfológicas e controle da fase cristalina. Uma maneira muito usual de produção destes materiais é o uso de surfactantes e polímeros, sendo que no presente trabalho foram utilizados quatro direcionadores, polietileno glicol (PEG 2000), sulfato de sódio dodecil (SDS), brometo de cetiltrimetilamônio (CTAB) e carboximetilcelulose (CMC). As sínteses foram preparadas utilizando uma solução etanólica de isopropóxido de titânio (1 mol/L), contendo ou não os direcionadores supracitados. As soluções foram solvotermalizadas no reator de micro-ondas em diferentes tempos de síntese (1, 30 e 60 min.), visando estudar o comportamento do material com o tempo de radiação. Foi obtidos materiais com altas áreas superficiais e diferentes morfologias com tamanho médio de partículas da ordem de 10-30 nm, os pós foram caracterizados por difratometria de raios-X (DRX), análise superficial de BET, espectroscopia na região do infravermelho (IV), espectroscopia Raman, espectroscopia na região do ultravioleta visível (UV-Vis) e microscopia eletrônica de varredura com emissão de campo (FE-MEV). A segunda etapa consiste na aplicação desses fotocatalisadores na fotodegradação do corante remazol amarelo ouro (RNL), onde observamos alta eficiência fotocatalítica do TiO2 e grande influência de propriedades como área superficial e morfológica na atividade de fotodegradação, obtendo cerca de 81% de descoloração usando o TiCMC, as reações foram realizadas utilizando um fotoreator a temperatura ambiente, com tempos de 1, 2 e 4 h sendo o corante caracterizado por espectroscopia na região do ultravioleta visível. A capacidade de fotodegradação foi comparada com a atividade fotocatalítica do TiO2 degussa P25.

Efluentes contendo resíduos perigosos ou substâncias orgânicas recalcitrantes são geradas em uma ampla variedade de processos industriais. O manejo inadequado destes efluentes pode causar contaminação das águas superficiais e subterrâneas. O seu tratamento por processos convencionais muitas vezes não é eficiente, por vezes impedindo o despejo ou reutilização de águas em unidades industriais. Os processos oxidativos avançados têm sido o foco de vários estudos em busca de alternativas viáveis para o tratamento de águas residuais contendo contaminantes orgânicos tóxicos, ou recalcitrantes. No presente estudo, o processo foto-Fenton é abordado, com a utilização de luz solar como fonte de fótons. O estudo consistiu de uma etapa de experimentos em um reator solar provido de coletores parabólicos compostos (CPC), ligados a um tanque agitado equipado com lâmpadas elétricas. Este sistema de operação foi utilizado em diferentes configurações, como operação em batelada ou contínuo, com variação de área irradiada por luz solar e com variação da potência total das lâmpadas no tanque. Na maior parte dos experimentos, com o reator operando em regime batelada, mais de 90% do carbono orgânico dissolvido (COD) foi removido em menos de 3 horas de irradiação solar, um desempenho equivalente ao de reatores baseados em fontes de luz artificial. Os dados experimentais foram usados no ajuste de modelos matemáticos empíricos baseados em redes neurais para simulação da taxa de remoção de COD em função das condições experimentais. Este modelo foi combinado com balanços de massa, que permite simular o desempenho do reator para diferentes valores das variáveis operacionais e de projeto. Os resultados das simulações do modelo mostraram boa concordância com os dados experimentais para a maioria dos casos. Além de evidenciar a relação entre as variáveis de processo, os resultados obtidos possibilitam identificar aspectos importantes no projeto de reatores baseados em radiação solar para tratamento de efluentes. / Wastewaters containing hazardous, or recalcitrant organic substances are generated in a wide variety of industrial processes. The inadequate management of these effluents can cause contamination of underground and surface water. Their treatment by conventional processes may not be technically efficient, and usually prevents effluents from being discarded or reused in industrial processing units. Photochemical advanced oxidation technologies can be a feasible alternative for wastewater treatment. In this study the photo-irradiated Fenton process is considered, with the aim of utilizing solar radiation as a photon source to the process. The study comprised experiments carried out in a solar reactor based on compound parabolic collectors (CPC) connected to a stirred tank equipped with electric lamps. This reaction system operated under different conditions, and different configurations (continuous and batch operation, different solar irradiated area, different electric power for the light sources in the stirred tank). In general, the performance of the solar reactor was similar to the performance of reactors based on electric light sources (for instance, in batch operation more than 90% of the dissolved organic carbon in solution (DOC) was removed in less than 3 hours). The experimental results were used to fit a neural network-based mathematical model to simulate the DOC removal rate as a function of the experimental conditions. This model was combined with mass balances, enabling to simulate the reactor performance for different values of the operating and design variables. The model results showed good agreement with most of the experiments. The simulation results enabled to evaluate the effect of the variables included in the study, and to identify important aspects related to reactor performance under different conditions of solar radiation and electric energy sources.