Orientador: José Roberto Guimarães / Tese (doutorado) - Universidade Estadual de Campinas, Faculdade de Engenharia Civil, Arquitetura e Urbanismo / Made available in DSpace on 2018-08-23T01:48:16Z (GMT). No. of bitstreams: 1 Silva_CaioAlexandreAugustoRodriguesda_D.pdf: 5160272 bytes, checksum: ae6b16aeb8851a3f7a722c3a4fb1e054 (MD5) Previous issue date: 2013 / Resumo: Nesse trabalho foi avaliada a degradação de flumequina (500 ?g L-1) por processo físico (fotólise-UV254), químico (peroxidação-H2O2) e oxidativos avançados (fotoperoxidação-UV/H2O2, fotocatálise heterogênea-UV/TiO2, reagente de Fenton-Fe(II)/H2O2, foto-Fenton-UV/Fe(II)/H2O2, eletroquímico e foto-eletroquímico) em um reator fotoquímico de recirculação em batelada. Os processos UV/H2O2 (CH2O2 inicial = 1,0 mmol L-1) e a fotocatálise (CTiO2 suspensão = 0,62 mmol L-1) foram os processos mais eficientes, reduzindo cerca de 85% da flumequina em 15 min de reação. A fotólise provocou a degradação da flumequina em 91,2% em 60 min de ensaio, enquanto que o processo foto-Fenton 94%, quando usados 10,0 e 0,25 mmol L-1 de H2O2 e Fe(II), respectivamente. Por outro lado, a peroxidação (CH2O2 = 1,0 mmol L-1) e o reagente de Fenton (CFe(II) = 2,0 mmol L-1 e CH2O2 = 0,5 mmol L-1) não atingiram mais de 10% e 40 % de degradação, respectivamente, após 60 min de reação. Os processos eletroquímico e foto-químico atingiram aproximadamente 82 e 85% de degradação da flumequina, após 60 min de reação quando aplicado 45 mA cm-2. A diminuição da atividade antimicrobiana das soluções submetidas aos processos oxidativos avançados foi proporcional à concentração residual da flumequina na solução. Não foi observada atividade antimicrobiana residual nas soluções submetidas aos seguintes processos oxidativos avançados e condições: UV/ H2O2 (CH2O2 = 1,0 mmol L-1, 30 min de reação), UV/TiO2 (CTiO2 = 0,62 mmol L-1, 30 min de reação), foto-Fenton (CFe(II) = 0,25 mmol L-1 e CH2O2 = 10 mmol L-1, 60 min de reação) e foto-eletroquímico (45 mA cm-2 e 60 min de reação). Os intermediários formados foram monitorados em 10, 15 e 30 min de reação nos processos oxidativos avançados e fotólise, e foi observado que os intermediários propostos possuíam uma atividade antimicrobiana menor que a flumequina. A eficiência dos processos UV/ H2O2 e UV/TiO2 (1,0 mmol L-1 e 0,62 mmol L-1 de H2O2 e TiO2) foi próximo a 100%, removendo totalmente a atividade antimicrobiana da solução / Abstract: This work evaluated the degradation of flumequine (500 ?g L-1) by physical process (photolysis-UV254), chemical process (H2O2 - peroxidation) and advanced oxidation processes (photoperoxidation - UV/H2O2, heterogeneous photocatalysis - UV/TiO2, Fenton's reagent - Fe(II)/H2O2, photo-Fenton - UV/Fe(II)/H2O2) in a batch-recirculation photochemical reactor. The processes UV/H2O2 (CH2O2 = 1.0 mmol L-1) and photocatalysis (CTiO2 suspension = 0.62 mmol L-1) are the most efficient ones, reducing about 85% of the flumequine in 15 min of reaction time. The photolysis caused 91.2% of flumequine degradation after 60 min of assay, while the photo-Fenton process degraded 94% of the drug when used 10.0 and 0.25 mmol L-1 of H2O2 and Fe(II), respectively. Moreover, peroxidation (CH2O2 = 1,0 mmol L-1) and Fenton's reagent (CFe(II) = 2.0 mmol L-1 and CH2O2 = 0.5 mmol L-1) did not achieve more than 10% and 40% degradation, respectively, after 60 min of reaction. Eletrochemical and photo-eletrochemical processes degraded about 82% and 85%, respectively, after 60 min of reaction at 45 mA cm-2. The decrease of the solutions antimicrobial activity subjected to advanced oxidation processes was proportional to the residual concentration of flumequine in the solution. There was no residual antimicrobial activity in the solutions subjected to the following advanced oxidation processes and conditions: UV/H2O2 (CH2O2 = 1.0 mmol L-1, 30 min of reaction), UV/TiO2 (CTiO2 = 0.62 mmol L-1, 30 min of reaction), photo-Fenton (CFe(II) = 0.25 mmol L-1 and CH2O2 = 10 mmol L-1, 60 min of reaction) and photo-eletrochemical (45 mA cm-2, 60 min of reaction). The intermediates formed were monitored at 10, 15 and 30 min of reaction in photolysis and advanced oxidation processes, where it was observed that the proposed byproducts owned a lower antimicrobial activity than flumequine. The efficiency of the processes UV/H2O2 and UV/TiO2 (1.0 mmol L-1 and 0.62 mmol L-1 of H2O2 and TiO2, respectively) was close to 100%, entirely removing the antimicrobial activity of the solution / Doutorado / Saneamento e Ambiente / Doutor em Engenharia Civil

Orientador: José Roberto Guimarães / Dissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Engenharia Civil, Arquitetura e Urbanismo / Made available in DSpace on 2018-08-19T19:11:27Z (GMT). No. of bitstreams: 1 Barbosa_IzabelaMajor_M.pdf: 2150780 bytes, checksum: 874939a28cdf8546758349402fb228e2 (MD5) Previous issue date: 2012 / Resumo: A abamectina é uma avermectina amplamente utilizada como antiparasitário na pecuária. Os processos selecionados para degradação do fármaco veterinário foram fotólise (UV), peroxidação (H2O2), peroxidação assistida por luz ultravioleta (UV/H2O2), reagente de Fenton e foto-Fenton. A concentração inicial de abamectina foi de 500 ?g L-1 e cada ensaio teve duração de 600 segundos... Observação: O resumo, na íntegra, poderá ser visualizado no texto completo da tese digital / Abstract: Abamectin is widely used as a pest control in livestock. Photolysis (UV), peroxidation (H2O2), peroxidation assisted by ultraviolet light (UV/H2O2), Fenton's reagent and photo- Fenton were selected for the degradation of this veterinary drug. The initial concentration of abamectin was 500 ?g L-1 and each test was carried out during 600 seconds....Note: The complete abstract is available with the full electronic digital thesis or dissertations / Mestrado / Saneamento e Ambiente / Mestre em Engenharia Civil

Orientador: José Roberto Guimarães / Tese (doutorado) - Universidade Estadual de Campinas, Faculdade de Engenharia Civil, Arquitetura e Urbanismo / Made available in DSpace on 2018-08-21T02:45:49Z (GMT). No. of bitstreams: 1 DalBosco_SandraMaria_D.pdf: 1640850 bytes, checksum: 320db8502d6cebf6f31820fec9e7739d (MD5) Previous issue date: 2012 / Resumo: Neste trabalho foi avaliada a degradação de ivermectina em solução aquosa (500 ?g L-1) pelos processos de peroxidação, fotólise, peroxidação assistida por luz ultravioleta, reagente de Fenton, foto-Fenton, fotocatálise com TiO2 em suspensão, eletroquímico e fotoeletroquímico. A peroxidação foi ineficaz independentemente da concentração de H2O2 utilizada (0,5 - 10 mmol L-1). A fotólise e a peroxidação assistida por luz ultravioleta apresentaram eficiências superiores a 98% em 300 s de reação (dose de 1.410 mJ cm-2). No processo de degradação Fenton, quando utilizado 1,0 mmol L-1de Fe(II) e 5,0 mmol L-1 de H2O2, a eficiência máxima foi de 80% em 60 s. No foto-Fenton as degradações atingiram 99 % em 600 s de reação. Na fotocatálise com TiO2 em suspensão houve uma degradação de 90% para uma dose de radiação de 1.410 mJ cm-2, e 97% para 2.820 mJ cm-2. No processo eletroquímico em 60 s de reação a eficiência foi entre 50 e 60%, e em 600 s entre 60 e 70% em todas as condições de densidade de corrente elétrica (13,6 a 40,9 mA cm-2) e concentrações de eletrólito suporte (0,01 a 0,25 mmol L-1 de K2SO4) avaliadas. O processo fotoeletroquímico apresentou eficiência de degradação próxima a 95% em 300 s de reação, independentemente das concentrações de eletrólito suporte e densidades de corrente elétrica empregadas. De forma geral, as reduções da toxicidade aguda, utilizando-se o microcrustáceo Daphnia similis como organismo-teste, foram diretamente proporcionais às eficiências de degradação. Ao final de 600 s não foi observada toxicidade nas soluções submetidas aos processos de fotólise, peroxidação assistida por luz ultravioleta, reagente de Fenton (1,0 e 5,0 mmol L-1 de Fe(II) e H2O2, respectivamente), foto-Fenton (todas as condições avaliadas) e fotocatálise com TiO2/H2O2 (0,12 e 0,01 mmol L-1 de TiO2 e H2O2, respectivamente) / Abstract: Ivermectin degradation (500 ?g L-1) by peroxidation, photolysis, peroxidation assisted by UV radiation, Fenton's reagent, photo-Fenton, photocatalysis with TiO2 in suspension, electrochemical, and photoelectrochemical processes were evaluated. Peroxidation was ineffective regardless of H2O2 concentration used (0.5 - 10 mmol L-1). The photolysis and peroxidation assisted by UV radiation reached 98% of degradation in 300 s of reaction (dose of 1410 mJ cm -2). The maximum efficiency in Fenton process was 80% for 60 s (1.0 mmol L-1 Fe(II) and 5.0 mmol L-1 H2O2. For photo-Fenton the degradation efficiency reached 99% in 600 s reaction. In photocatalysis assays the degradation was 90% for a radiation dose of 1410 mJ cm-2 and 97% for 2820 mJ cm-2. In the electrochemical process the efficiency ranged from 50% to 60% in 60 s of reaction and from 60% to 70% in 600 s when the current density ranged from 13.6 to 40.9 mA cm-2 (supporting electrolyte concentration of 0.01 and 0.25 mmol L-1). The photoelectrochemical process presented 95% of degradation efficiency in 300 s of reaction, regardless of the electrolyte concentrations and electrical current densities employed. In general, the acute toxicity reductions using the micro-organism Daphnia similis as organism-test were directly proportional to the efficiencies of degradation. In 600 s of the reaction, no toxicity was observed in the solution submitted to photolysis, peroxidation assisted by UV radiation, Fenton's reagent (1.0 mmol L-1 of Fe(II) and 5.0 mmol L-1 of H2O2), photo-Fenton (all conditions studied), and photocatalysis with TiO2/H2O2 (0.12 and 0.01 mmol L-1 of TiO2 and H2O2, respectively) processes / Doutorado / Saneamento e Ambiente / Doutora em Engenharia Civil

The presence of trace organic compounds (TOrCs) in wastewater effluent and surface waters has raised attention due to their health and environmental effects. Some TOrCs are naturally attenuated via biodegradation, photo-degradation and/or adsorption, but some persist in the environment as contaminants in surface and ground waters. Thus, it is crucially important to understand their transformation pathways and their mechanisms following their discharge into the environment. This work presents research in three parts: • The first part represents an investigation of photo-transformation of TOrCs (e.g., furfuryl alcohol, p-cresol, gemfibrozil) under UV254, UVA and natural sunlight, and involving reactive oxygen species including singlet oxygen, hydroxyl radicals, triplet excited states, and specific inorganic radicals that are created by effluent organic matter (EfOM). Singlet oxygen was the only ROS, generated from effluent organic matter (EfOM) that mainly contributed to the photo-transformation of these selected TOrCs. A comprehensive mechanism and complementary kinetic model were proposed to predict the trajectories of TOrC removals via reaction with singlet oxygen. Simulations built on predicted quantum efficiencies accounted for light shading and competitive effects. Agreement between measurements and simulations was excellent. • The second part of the dissertation summarizes expected removal efficiencies for fifty-five TOrCs in alternative engineered and natural treatment processes including conventional biological treatment, advanced oxidation processes (AOP), reverse osmosis (RO), granular activated carbon (GAC), and sunlight photolysis. • The last section of the dissertation follows the trajectories of a series of TOrCs and total estrogenic activity in the Santa Cruz River, following their discharge from a wastewater treatment plant in the Tucson area. The study suggests that some TOrCs tend to persist in the environment while others experience photo (or other) transformations that diminish their concentrations or activities with distance and time of travel in the river. The attenuation of estrogenic activity was dependent on sunlight and the presence of specific (unidentified) wastewater components.

Visible light-driven photocatalysis has shown considerable potential in the area of clean and renewable energy, as well as in wastewater treatment. This thesis describes the synthesis, characterization and applicability of a visible-light active photocatalyst, bismuth oxybromide (BiOBr). The photocatalytic activity of BiOBr was investigated through its preparation via hydrothermal and solvothermal synthesis routes under various conditions. Hydrothermal catalyst was prepared using non template based method while for solvothermal synthesis CTAB was used as a template. Parameters of temperature and time of thermal treatment were optimized for each synthesis method and overall tests for catalyst dosage and recyclability were performed. An overall optimal route leading to high photocatalytic performance was also proposed based on the obtained results. Studies were also conducted to examine the applicability of optimally synthesized BiOBr in drinking water applications by studying catalyst-mediated disinfection of E. coli and degradation of phenol. Favourable results were obtained, confirming the prospective application of BiOBr as a viable photocatalyst for disinfection. Furthermore, the potential of enhancing BiOBr to further improve its performance is described through synthesis of a novel PdCl2/BiOBr based photocatalyst. Overall, the performance of BiOBr under various conditions in this study establishes its potential as a holistic photocatalyst and merits further development.

Due to their potential health impact on human beings and ecosystems, persistent trace organic compounds (TOrCs) have aroused concern from both the public and professionals. In particular, the discharge of pharmaceuticals, endocrine disrupters, disinfection byproducts and other TOrCs from wastewater treatment plants into the environment is an area of extensive current research. This work studies the fate and treatments of TOrCs, with emphases on advanced oxidation processes (AOPs). This work presents predicted removal efficiencies of a variety of engineered and natural processes for 55 frequently encountered TOrCs in treated wastewater, based on previously reported data and using existing predictive models. Correlations between physicochemical and biological properties of TOrCs and treatment performance were explored. Removal of TOrCs in all processes investigated in this study was found to be sensitive to matrix effects. Heuristic guidelines for selection of sequenced treatment processes for TOrCs management were established. A field reconnaissance of natural process of TOrCs was conducted by analyzing the occurrence and fate of a suite of TOrCs, as well as estrogenic activity in water and sediments in the Santa Cruz River, an effluent-dependent stream in Tucson, Arizona. Some TOrCs, including contributors to estrogenic activity, were rapidly attenuated with distance of travel in the river. TOrCs that have low biodegradability and low octanolwater partitioning coefficients were less removed. Results of independent experiments indicated potential indirect photodegradation of estrogenic compound by reactive species generated from photolysis of effluent organic matter. Utilizing advanced oxidation processes (AOPs) as tertiary water and wastewater treatment is an option to prevent discharge of TOrCs into the environment. Compared to conventional AOPs, the ability of generating hydroxyl radicals (•OH) without additional doses of hydrogen peroxide (H2O2) or ozone makes ultraviolet (UV) photolysis of ferric hydroxo complexes a novel AOP, especially in acidic environments. A Fe(III)/UV254 kinetic model, which combines Fenton-like mechanism, and photolyses of Fe3+, FeOH2+ and H2O2 was proposed and experimentally validated to predict Fenton-like and H2O2 direct UV254 photolysis scenarios, individually. Nevertheless, the model underestimated the ferrous ion development during Fe(III)/UV254 photolysis, perhaps due to the overprediction of the oxidation of Fe2+ by •OH. The UV/H2O2 AOP was also studied in this work. A predictive kinetic model was developed to evaluate process efficiency of oxidation of p-cresol by UV/H2O2 photolysis based on a complete reaction mechanism, including reactions of intermediates with •OH. Results of this study highlight the significance of consideration of radical scavenging effects by the byproducts from oxidation of organic matter in model prediction performance.

Os poluentes orgânicos emergentes (POE) são compostos químicos presentes numa variedade de produtos comerciais como medicamentos, produtos de higiene, agrotóxicos, surfactantes, dentre outros, podendo ser encontrados em matrizes ambientais e biológicas. Esses poluentes não são usualmente monitorados ou ainda não possuem legislação regulatória correspondente, mas apresentam risco à saúde humana e ao meio ambiente. Dentre esses POE, podemos destacar o nonilfenol etoxilado, um surfactante não-iônico utilizado no desengraxe alcalino da indústria de galvanoplastia. Esse surfactante possui uma recalcitrância e toxidade que aumenta com a diminuição do número de grupos etoxilados, processo que ocorre quando ele é biodegradado. Alguns dos produtos da biodegradação são o nonilfenol com 4, 3, 2 ou 1 grau de etoxilação e nonilfenol, este considerado disruptor endócrino imitando o hormônio natural 17β-estradiol. Tratamentos convencionais de efluentes e água não são eficientes para degradação completa desses compostos. O emprego de processos mais eficientes, como processos oxidativos e oxidativos avançados tais como a Eletrólise (E), Fotólise direta (F), Fotocatálise heterogênea (FH) e a fotoeletrooxidação (FEO), tecnologias limpas que utilizam o elétron e o fóton como reagentes, têm sido proposto como opção para a degradação desses compostos, evitando assim a contaminação dos recursos hídricos. Este trabalho foi realizado com uma solução baseada na composição de um efluente industrial contendo nonilfenol etoxilado com 4 graus de etoxilação. Os ensaios de FEO foram realizados em triplicata, variando-se a densidade de corrente, potência de lâmpada e o tempo de tratamento. Além disso, foram realizados, para efeito de comparação e elucidação de mecanismos, ensaios de eletrólise, fotólise direta e fotocatálise heterogêna. As amostras coletadas antes e após os processos oxidativos foram caracterizadas por diferentes métodos analíticos e por toxicidade. Verificou-se que no tempo de tratamento de 240 minutos as diferentes configurações de FEO não foram suficientemente eficazes na degradação de todo o poluente que se encontra na solução inicial, entretanto, a configuração FEO3 não gerou metabólitos mais tóxicos, não apresentou diferença de germinação e de crescimento de raiz, não apresentando também citotoxicidade e genotoxicidade em alface e em cebola, apresentando toxicidade apenas em peixes em uma concentração de 70,71%, o que pode ser evitado com o aumentando do tempo de tratamento, à vista disso, o processo de FEO torna-se uma opção na degradação do nonilfenol etoxilado e de outros POE, evitando assim que esses atinjam os recursos hídricos. / The emerging organic pollutants (POE) are chemical compounds present in a variety of commercial products such as medicines, toiletries, pesticides, surfactants, among others, can be found in environmental and biological matrices. These pollutants are usually not monitored or have no corresponding regulatory legislation, but present risk to human health and the environment. POE Among these, we highlight the nonylphenol ethoxylate, one non-ionic surfactant used in degreasing alkaline electroplating industry. This surfactant has a recalcitrance and toxicity increases with the decrease of the number of ethoxylate groups, a process which occurs when it is biodegraded. Some of the products of biodegradation are nonylphenol with 4, 3, 2 or 1 degree of ethoxylation of nonylphenol and this considered endocrine disruptor mimicking the natural hormone 17β -estradiol. Conventional treatment of sewage and water are not efficient for complete degradation of these compounds. The use of more efficient processes, such as oxidation and advanced oxidation processes such as direct photolysis (F), Electrolysis (E), heterogeneous photocatalysis (FH) and photoelectrooxidation (FEO), clean technologies that utilize the electron and photon reagents have been proposed as an option to the degradation of such compounds, thereby avoiding the contamination of water resources. This work was carried out with a solution based on the composition of an industrial effluent containing nonylphenol ethoxylate with 4 degrees of ethoxylation. FEO assays were performed in triplicate, by varying the current density lamp power and treatment time. In addition, we performed, for comparison and elucidation of mechanisms, testing electrolysis, photolysis and photocatalysis heterogenous. The samples collected before and after the oxidative processes were characterized by different analytical methods and toxicity. It was found that treatment time of 240 minutes, the FEO different configurations were not efficient enough to degrade any pollutants that is in the initial solution, however, the configuration FEO3 not more toxic metabolites generated no significant difference in seed germination and root growth, no significant cytotoxicity and genotoxicity also in lettuce and onion, showing toxicity on fish only at a concentration of 70.71 %, which can be avoided by increasing treatment time, the sight, the process of FEO becomes an option in the degradation of nonylphenol ethoxylate and other POE, thus preventing it reaches the water.

Orientador: José Roberto Guimarães / Dissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Engenharia Civil, Arquitetura e Urbanismo / Made available in DSpace on 2018-08-24T08:56:07Z (GMT). No. of bitstreams: 1 Peres_MarcelaSouza_M.pdf: 1942738 bytes, checksum: e568a9f4c6bc9579df4ca7bc831e9085 (MD5) Previous issue date: 2014 / Resumo: A ofloxacina é um antimicrobiano de amplo espectro frequentemente encontrado em concentrações significativas em efluentes e águas superficiais. A contínua introdução deste fármaco no meio ambiente constitui um risco potencial em longo prazo para os organismos não alvos ou para a saúde humana. Neste estudo foi avaliada a degradação da ofloxacina pelos processos oxidativos avançados (POA) peroxidação assistida por radiação ultravioleta (UV/H2O2) e fotocatálise (UV/TiO2 e UV/TiO2/H2O2). Foi avaliada também a atividade antimicrobiana residual do fármaco, utilizando a bactéria E. coli, e a toxicidade aguda (Vibrio fischeri). A concentração de ofloxacina foi monitorada utilizando-se cromatografia líquida de alta eficiência (CLAE). Os resultados obtidos indicam que os POA aplicados foram eficientes para a degradação desse fármaco. O processo UV/H2O2 alcançou degradação de 99%, após 60 min de reação. Para o processo UV/TiO2, a eficiência de degradação obtida foi de 89,3% após 60 min e a adição de peróxido de hidrogênio elevou a eficiência para 97,8%. A atividade antimicrobiana do fármaco foi reduzida consideravelmente, alcançando 95% de remoção com a aplicação do UV/H2O2 e 96% utilizando o processo UV/TiO2/H2O2. A toxicidade das amostras não aumentou no decorrer da aplicação destes POA, indicando a potencial utilização destes processos para o tratamento de soluções aquosas contendo ofloxacina / Abstract: Ofloxacin is a broad-spectrum antimicrobial agent which is frequently found in significant concentrations in wastewater and surface water. Its continuous introduction into the environment constitutes a potential risk to non-target organisms or to human health. This study evaluated ofloxacin degradation by the UV/H2O2, UV/TiO2 and UV/TiO2/H2O2 advanced oxidation process (AOPs), residual antimicrobial activity (E. coli), and acute toxicity (Vibrio fischeri). Ofloxacin concentration was monitored with HPLC analyses. The results obtained shown that AOPs applied were efficient for ofloxacin degradation. For UV/H2O2, degradation efficiency was 99% in 60 min of reaction. For UV/TiO2, degradation efficiency was 89.3% in 60 min of reaction when applied 128 mg L-1 TiO2. The addition of 1.68 mmol L-1 of hydrogen peroxide increased the degradation to 97.8%. For both processes, the antimicrobial activity was considerably reduced throughout the reaction, reaching 95% removal when UV/H2O2 was applied and 96% using the UV/TiO2/H2O2 process. The toxicity of the samples did not increase during AOP application, indicating the potential use of these processes for the treatment of aqueous solutions containing ofloxacin / Mestrado / Saneamento e Ambiente / Mestra em Engenharia Civil

En las últimas décadas, los procesos redox fotoinducidos mediados por luz visible han recibido gran atención debido a las suaves condiciones de operación en que se llevan a cabo. Como resultado, se han logrado posicionar como una alternativa más dentro de los Procesos de Oxidación Avanzada. Además, se han convertido en una metodología excepcional en síntesis orgánica, que ha abierto la puerta a nuevas rutas químicas con aplicaciones sintéticas. Sin embargo, a pesar del crecimiento del campo, se ha prestado poca atención a los mecanismos por los que operan estos procesos. El principal objetivo de esta tesis fue avanzar en la comprensión de distintos procesos fotoredox llevados a cabo empleando fotocatalizadores orgánicos. Más específicamente, se estudió la viabilidad de distintos fotocatalizadores orgánicos, y además, se realizó un estudio mecanístico detallado basado en técnicas resueltas en el tiempo. A partir de estos resultados, se estableció una metodología para determinar los puntos clave a considerar en un sistema fotoredox. En primer lugar, en la Parte I, se eligieron dos fotocatalizadores basados en sales de pirilio y tiapirilio, que operan mediante transferencia electrónica oxidativa, con distintos objetivos. En el Capítulo 3, se evaluó su aplicabilidad en la fotodegradación de dos contaminantes de la industria del corcho y se estudió el mecanismo por el que se produce dicha fotodegradación. En el Capítulo 4, se demostró la utilidad de la detección directa de todos los intermedios de vida corta derivados del TPP+ implicados en la oxidación fotocatalizada como herramienta para evaluar el nivel de fotodegradación. En el Capítulo 5, se empleó TPTP+ para establecer las mejores características de un fotocatalizador y la influencia de la concentración de las sustancias a oxidar en la eficiencia de los estados excitados, o en general, de los intermedios clave de vida corta. En segundo lugar, en la Parte II, en el Capítulo 6, se evaluó el potencial del Rosa Bengala en la eliminación de dos fármacos. Éste es un fotocatalizador típico en la remediación de aguas residuales conocido por actuar via mecanismo Tipo II. Se incluyó además un segundo fotocatalizador, Perinaftenona, cuyo rendimiento cuántico de oxígeno singlete es incluso mayor a Rosa Bengala. En el Capítulo 7, se llevó a cabo la fotooxidación de tres contaminantes, usando NMQ+, un fotocatalizador inusual, capaz de generar oxígeno singlete desde su estado excitado singlete. En todos los casos se pudo demostrar la mayor contribución del mecanismo Tipo I sobre el mecanismo Tipo II en la fotodegradación de los diferentes contaminantes. Finalmente, en la Parte II, el Capítulo 8 se dedicó a la reducción fotocatalítica de bromuros orgánicos, empleando Riboflavina, un colorante orgánico no metálico, como fotocatalizador. De nuevo, se prestó especial atención a la detección y comportamiento de las especies intermedias, lo que resultó de acuerdo a los datos termodinámicos. / En les últimes dècades, els processos redox fotoinduïts mitjan per llum visible han rebut gran atenció degut a les suaus condicions d'operació en que es donen. Com a resultat, s'han aconseguit col·locar com una alternativa mes dins dels Processos d'Oxidació Avançada. A més, han estat convertint-se en una metodologia excepcional en síntesi orgànica, que ha obert la porta a noves rutes químiques amb aplicacions sintètiques. No obstant això, a pesar del creixement del camp, s'ha prestat poca atenció als mecanismes pels que operen aquests processos. El principal objectiu d'esta tesi va ser avançar en la comprensió de diferents processos fotoredox duts a terme emprant fotocatalitzadors orgànics. Més específicament, es va estudiar la viabilitat de distints fotocatalitzadors orgànics, i a més, es va realitzar un estudi mecanístic al detall basat en tècniques resoltes en el temps. Amb aquests resultats, es va establir una metodologia per a determinar els punts clau a considerar en un sistema fotoredox. En primer lloc, en la Part I, es van elegir dos fotocatalitzadors basats en sals de pirili i tiapirili, els quals operen per mitjà de transferència electrònica oxidativa, amb distints objectius. En el Capítol 3, es va avaluar la seua aplicabilitat en la fotodegradació de dos contaminants de la indústria del suro i es va estudiar el mecanisme pel qual es produeix dita fotodegradació. En el Capítol 4, es va demostrar la utilitat de la detecció directa de tots els intermedis de curt temps de vida derivats del TPP+ implicats en l'oxidació fotocatalitzada com a ferramenta per avaluar el nivell de fotodegradació. En el Capítol 5, es va emprar TPTP+ per a establir les millors característiques d'un fotocatalitzador i l'influencia de la concentració de les substàncies a oxidar en la eficiència dels estats oxidats, o en general, del intermedis claus de vida curta. En segon lloc, en la Part II, en el Capítol 6, es va avaluar el potencial del Rosa Bengala en l'eliminació de dos fàrmacs. Aquest es un fotocatalitzador típic en la remediació d'aigües residuals conegut per actuar via mecanisme Tipus II. Es va incloure a més un segon fotocatalitzador, Perinaftenona, el del qual rendiment quàntic d'oxigen singlet és inclús major a Rosa Bengala. En el Capítol 7, es va dur a terme la fotooxidació de tres contaminants, usant NMQ+, un fotocatalitzador inusual, capaç de generar oxigen singlet des del seu estat excitat singlet. En tots els casos es va poder demostrar la major contribució del mecanisme Tipus I sobre el mecanisme Tipo II en la fotodegradació dels diferents contaminants. Finalment, en la Part II, el Capítol 8 es va dedicar a la reducció fotocatalítica de bromurs orgànics, emprant Riboflavina, un colorant orgànic no metàl·lic, com fotocatalitzador. De nou, es va prestar especial atenció a la detecció i comportament de les espècies intermèdies, el que va resultar d'acord amb les dades termodinàmiques. / In the last decades, photoinduced-redox processes mediated through visible light have obtained great attention due to the generally mild operating conditions that they offer. As a result, they constitute a further alternative within the so-called Advanced Oxidation processes. Besides, they are becoming an outstanding methodology in organic synthesis, which has opened the door to new synthetic and chemical routes. However, despite the growth of the field, little attention has been paid to the mechanisms pathways behind these processes. The main objective of this thesis was to gain deeper understanding of different photoredox processes carried out using organic photocatalysts. More specifically, the viability of several organic photocatalysts was studied, and besides, a careful mechanistic study based on time resolved techniques supported the postulated mechanisms. With this information, a methodology determining the key points to consider in a photoredox system were stablished. Firstly, in Part I, two photocatalysts based on pyrilium and thiapyrilium salts, which operate through an oxidative electron transfer, have been used with different objectives. In Chapter 3, the viability of the photodegradation of two common pollutants from cork industry and the mechanism behind it has been evaluated. In Chapter 4, the direct detection of all the TPP+ derived short-lived intermediates in the photocatalyzed oxidation of a mixture of pollutants using TPP+ was proposed as a methodology to assess the photodegradation extent. In the last chapter of Part I, Chapter 5, TPTP+ is used to stablish the best characteristics of a photocatalyst. Besides, the study claimed the influence of the concentration of the target substances in the efficiency of the excited states or, in general, of the key short-lived intermediates. Secondly, in Part II, in Chapter 6, Rose Bengal, a typical photocatalyst used in wastewater remediation, known for working via Type II mechanism, was evaluated for the removal of two common drugs. In addition, a second one, Perinaphtenone, which exhibits even a higher singlet oxygen quantum yield than Rose Bengal was tested. In Chapter 7, NMQ+, a non-typical photocatalyst able of generate singlet oxygen from its singlet excited state, was used in the photooxidation of three different pollutants. In every case, the major contribution of Type I vs Type II mechanism was demonstrated. Finally, in Part III, Chapter 8 was devoted to the photocatalytic reduction of organic bromides. In this case, Riboflavine, a non-metallic organic dye, was used as a photocatalyst. Analogously, careful attention was paid to the behavoiur of the intermediates, which were in agreement, as well as to the thermodynamics of the steps involved in the photocatalytic cycle. / Martínez Haya, R. (2018). Photoredox catalysis for environmental and chemical applications. A mechanistically-based approach [Tesis doctoral no publicada]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/114828 / TESIS

With a growing population and continuous accumulation of pollutants, water resources worldwide are quickly being depleted. Drastic improvements need to be made in both water conservation and treatment. Advanced oxidation processes (AOPs) have been developed to go above and beyond the capabilities of traditional wastewater treatment facilities to eliminate emerging contaminants from our water systems. AOPs increase the generation of hydroxyl radicals (•OH) in oxidation reactions, which are less selective and more reactive than other oxidants, such as ozone, so they are more effective at degrading persistent compounds. This study explored an AOP that utilizes ozonated multi-walled carbon nanotubes (MWCNTs) to generate •OH; past research has proven the success of this method of water treatment, showing a significant decrease in the effluent concentration of the tested compounds. However, these previous studies used a batch system with an initial aliquot of ozone, which would not be a feasible option in a commercial application. This research compares results from a semi-batch system with a continuous injection of ozone to these previous batch system studies to determine if continuous ozonation improves •OH generation capability, contaminant degradation, and the associated reaction kinetics. Results from batch studies had shown limitations to both •OH generation and contaminant degradation which were suspected to be due to ozone degradation; however, these results suggest that ozone availability is in fact not a limiting factor to •OH or contaminant degradation, and another mechanism must be at play. Further, to advance the AOP toward a commercially feasible design, a continuous flow-through system with a MWCNT embedded membrane was explored. The continuous system achieved 80% contaminant degradation in some cases, however, with varying retention times and efficiencies over time, the results were inconclusive and additional experimentation is required.