Experimental Evaluation and Modeling of Photocatalytic Oxidation Air Cleaners

Heterogeneous ultraviolet photocatalytic oxidation (UV-PCO), as a promising advanced oxidation technology, has been suggested as an alternative and energy efficient method to improve indoor air quality (IAQ) through the photocatalytic degradation of indoor air pollutants. However, the complicated PCO reaction mechanisms and unexpected intermediates still need to be further explored in order for this technology to be successfully applied in mechanically ventilated buildings. Two main objectives of this study include the development of methodologies to evaluate the performance of PCO systems and the development of a reliable mathematical model to fully simulate the performance of these systems. A pilot four-parallel duct system was set-up to equitably and thoroughly evaluate the performance of UV-PCO air cleaners under the conditions relevant to the actual applications for a wide range of indoor air pollutants. This study investigated the UV-PCO removal efficiency of two types of air filters (fiberglass fibers coated with TiO2 (TiO2/FGFs) and carbon cloth fibers loaded with TiO2 (TiO2/CCFs)) under ultraviolet C (UVC) and vacuum ultraviolet (VUV) illumination. A systematic parametric evaluation of the effects of various kinetic parameters, such as types of pollutants, inlet concentration, airflow rate, light intensity, and relative humidity that influence the PCO performance, was conducted. In addition, gas-phase ozonation with a variety of chemical compounds was first examined when ozone was produced by VUV. Moreover, the formation of by-products generated from incomplete conversion was investigated to evaluate its impact on IAQ. A time-dependent model was proposed for predicting the performance of an in-duct PCO air cleaner under the conditions relevant to the actual applications. A comprehensive model was developed by integrating light scattering model, reaction kinetic model, mass balance as well as optional ozonation model. The UV-PCO model and the UV-PCO ozonation integrated model were validated with experimental results; there was a good agreement between the model prediction and the experiment result. The relative rate-limiting process between physical interactions and photochemical interactions was fully investigated through simulation analysis. Depending on the physical properties of the catalyst, reactor geometries, operation conditions, as well as environmental conditions, the photochemical reaction occurring on the fixed active sites at the catalyst surface is the dominating process for this PCO system

International Lighting in Controlled Environments Workshop

Lighting is a central and critical aspect of control in environmental research for plant research and is gaining recognition as a significant factor to control carefully for animal and human research. Thus this workshop was convened to reevaluate the technology that is available today and to work toward developing guidelines for the most effective use of lighting in controlled environments with emphasis on lighting for plants but also to initiate interest in the development of improved guidelines for human and animal research

Evaluation of UV-PCO Air Cleaners Performance at Low Level VOCs Concentration

Volatile organic compounds (VOCs) constitute the vast majority of indoor air contaminants. In design of ultraviolet photo-catalytic oxidation (UV-PCO) air cleaner system, the focus must be in selecting an appropriate catalyst that can transform all contaminants to harmless gases. Some produced contaminants may promote or inhibit the photocatalytic reactions, or even lead to deactivation of the catalyst. The PCO reactions of two classes of VOCs, light alcohols and alkanes (C5-C10) were studied with different types of nano titanium dioxide catalysts. The influence of relative humidity on oxidation rate of tested VOCs was discussed in detail to establish ideal operational conditions for the selected group of VOCs. A series of laboratory experiments was conducted with a pilot four-parallel duct system setup to test the VOCs in very low concentration levels which represents a typical indoor air environment. The experiments were carried out with different types of nano TiO2 catalysts with UV lamps. A new type of titanium dioxide catalyst was specifically developed for this study to enhance the efficiency of PCO system. A systematic method was used to develop and test the synthesized photocatalysts, which helped to improve the overall performance of test system. The performance of different catalysts was studied at different humidity conditions and different VOCs concentrations. The research objective was to develop a correlation between the PCO kinetic rate constants and physical characteristics of indoor VOCs. These correlations may be employed to eliminate the need of further experiments with every individual VOCs and they also could facilitate the design process of future PCO air cleaner. The physical characteristics of VOCs were used to estimate the performance of the PCO catalysts in a steady-state environmental test condition. The photocatalytic removal efficiency of VOCs and formation of intermediates and byproducts were studied with and without ozone generation UV lamps

From 280 to 700 nm: combining solar disinfection and phycotechnology for the recovery of resources from marine fish farming streams

La presente Tesis Doctoral se centra en el estudio de la combinación de dos tecnologías solares para el aprovechamiento de corrientes piscícolas desde una perspectiva de economía circular. Así, se ha estudiado el uso de la desinfección solar (SODIS) como pretratamiento para reducir la carga bacteriana de una corriente piscícola y la utilización de este efluente desinfectado como medio de cultivo para la producción de microalgas y la reducción del flujo másico de nutrientes. Se ha comprobado que el uso conjunto de ambas tecnologías solares genera una corriente de agua con calidad suficiente como para ser reintroducida al sistema de producción piscícola o ser vertida con seguridad al medio natural. De manera simultánea, el proceso genera biomasa de microalgas que puede ser reintroducida al sistema como ingrediente sustitutivo de harina de pescado en piensos de engorde para peces. En primer lugar, se seleccionó el marco en el que se aplicaría posteriormente la combinación de tecnologías solares, evaluando dos sistemas productivos piscícolas diferentes, de flujo continuo (FTS) y de recirculación (RAS). Con respecto a la desinfección solar, se llegó a la conclusión que el reactor tipo raceway era el más adecuado para llevar a cabo la desinfección solar a mayor escala por motivos tecno-económicos (menor inversión inicial y requerimiento de superficie en comparación con el tradicional colector parabólico compuesto, CPC). Se determinó que para desinfectar las corrientes estudiadas con concentración de bacterias (Vibrio spp.) de 103 UFC mL-1, la concentración óptima de peróxido de hidrógeno fue de 1.25 mg L-1. En estas condiciones se obtiene una eliminación superior al 99 % en t30 = 44 min (dosis = 22 Wh m-2), no observándose recrecimiento posterior ni efecto tóxico del oxidante residual sobre el posterior cultivo de microalgas. En el caso del cultivo de microalgas, se estudiaron un total de 6 especies (Nannochloropsis gaditana, Pavlova lutheri, Isochrysis galbana, Tetraselmis chuii, Phaeodactylum tricornutum, Chaetoceros gracilis) y un bloom a escala de laboratorio (18 L), obteniéndose productividades de entre 7 y 71 mg L-1 d-1 y velocidades de consumo de nitrógeno disuelto de entre 0,15 y 12,6 mg L-1 d-1. Gracias a los datos obtenidos a escala de laboratorio se diseñaron y construyeron dos reactores raceway, uno para desinfección solar (1000 L) y otro para el cultivo de microalgas (6000 L). Se situaron en la instalación de producción de 450 t año-1 de lenguados de la empresa Cultivos Piscícolas Marinos S.A. (CUPIMAR), empleándose como alimentación la corriente de purga del RAS enriquecida con 1 mg L-1 de fósforo. Se cultivó T. chuii debido a una mayor productividad (15 – 78 mg L-1 d-1) y concentración de proteínas (36 – 50 %) y se caracterizó tanto el efluente como la biomasa de microalgas generados a escala piloto. Se formularon dos piensos para lenguados incluyendo un 10 y un 20 % de biomasa algal (T. chuii), reduciendo el contenido en harina de pescado en un 25 %. En los ensayos de engorde de juveniles de lenguado con ambos piensos experimentales, no se encontraron diferencias significativas en la tasa de crecimiento ni en la composición proximal del pescado producido con respecto al control. El análisis tecno-económico mostró que el tratamiento del caudal de purga del RAS de una planta de producción de lenguados (Solea senegalensis) mediante una combinación de tecnología de microalgas y pretratamiento con desinfección solar tendría un coste de 0,52 € m-3, comparable con el coste de tratamiento de las aguas residuales urbanas. Además, gracias al ingreso que supondría la venta de la biomasa generada, este coste podría verse reducido hasta 0,33 € m-3.This Doctoral Thesis is focused on investigating two solar technologies for the use of fish farm streams from a circular economy perspective. Thus, the use of solar disinfection (SODIS) has been studied as a pretreatment to reduce the bacterial load of a fish stream and the use of this effluent as a culture medium for the production of microalgae and the reduction of the mass flow of nutrients. The combined use of both solar technologies will generate a water stream of sufficient quality to be reintroduced to the fish production system or to be safely discharged to the natural environment and, simultaneously, produce microalgae biomass that can be reintroduced to the system as a substitute ingredient for fishmeal in fish feed. First, two different fish production systems, flow through system (FTS) and recirculation aquaculture system (RAS), were studied to produce microalgae. The results indicate that the raceway type reactor is the optimum for solar disinfection on a larger scale for techno-economic reasons (lower initial investment and surface area requirement compared to the traditional compound parabolic collector, CPC). It was determined that, for disinfection of the studied streams, with bacteria concentration (Vibrio spp.) between 102 - 106 CFU mL-1 , the optimum concentration of hydrogen peroxide is 1 - 10 mg L-1 , oxidant concentrations that do not inhibit the subsequent biological process. In the case of microalgae culture, a total of six species (Nannochloropsis gaditana, Pavlova lutheri, Isochrysis galbana, Tetraselmis chuii, Phaeodactylum tricornutum, Chaetoceros gracilis) and a bloom were studied at laboratory scale (18 L), obtaining productivities between 7 and 71 mg L-1 d-1 and dissolved nitrogen consumption rates between 0.15 and 12.6 mg L-1 d-1 . Thanks to the data obtained at laboratory scale, two raceway reactors were designed and constructed, one for solar disinfection (1000 L) and the other for microalgae cultivation (6000 L). They were located in a 450 t year-1 sole production facility of Cultivos Piscícolas Marinos S.A. (CUPIMAR), using the RAS purge stream enriched with phosphorus up to 1 mg L-1 as culture medium. T. chuii was cultured due to higher productivity (15 - 78 mg L-1 d-1) and protein concentration (36 - 50 %), and both the effluent and the microalgae biomass generated at pilot scale were characterised. Two sole feeds were formulated, including 10 and 20 % algal biomass (T. chuii), reducing the fishmeal content by 25 %. In juvenile sole fattening trials with both experimental feeds, no significant differences were found in the growth rate and proximal composition of the fish produced concerning the control. The techno-economic analysis shows that the treatment of the RAS purge flow from a sole (Solea senegalensis) production plant using a combination of microalgae technology and pre-treatment with solar disinfection would cost 0,52 € m-3, comparable to the cost of urban wastewater treatment. Moreover, due to the income from the sale of the biomass produced, this cost could be reduced to 0,33 € m-3.Esta Tesis Doctoral ha sido realizada en el Grupo de Investigación Tecnología del Medio Ambiente (TEP-181) del Plan de Investigación Andaluz y gracias al contrato pre-doctoral de Personal Investigador en Formación (PIF) de la Universidad de Cádiz (UCA/REC01VI/2017). El trabajo experimental ha sido financiado por el proyecto AGL2016-80507-R, “Gestión eficiente y sostenible de efluentes en acuicultura marina mediante tecnología solar (Proyecto SUNRAS), del plan estatal de investigación científica y técnica y de innovación 2013 – 2016 del Ministerio de Economía y Competitividad, con periodo de ejecución 2017 – 2020

Assessment of novel Advanced Oxidation Processes for the Simultaneous Disinfection and Decontamination of Water

[ES] El mundo se enfrenta a una profunda crisis asociada al agua y la reutilización de aguas residuales urbanas (UWW), especialmente en agricultura, se presenta como una posible solución para abordar este problema. No obstante, la reutilización se debe promover dentro de unos límites mínimos de calidad del agua, los cuales pueden alcanzarse mediante la implementación de eficientes tratamientos terciaros en las actuales plantas de tratamiento de aguas residuales urbanas. En las últimas décadas, los Procesos de Oxidación Avanzada (POA), basados en la generación de especies reactivas del oxígeno altamente oxidantes y no selectivas, se han planteado como alternativa a los tratamientos convencionales para desinfección y descontaminación de agua residual. El objetivo general de este estudio es, por tanto, la evaluación de nuevos POA para desinfección y descontaminación simultánea de agua, investigando: (i) fotocatálisis heterogénea solar con ZnO modificado (Ce, Yb y Fe) y TiO2-P25 de referencia, (ii) peroximonosulfato (PMS) bajo radiación solar natural (PMS/Solar), (iii) POA basados en radical sulfato utilizando PMS y radiación UV-C (PMS/UV-C) y (iv) combinación de ZnO modificado con PMS como estrategia de tratamiento. Los objetivos biológicos y químicos analizados en este estudio fueron: tres patógenos de impacto en salud humana (dos bacterias gram-negativas Escherichia coli, Pseudomonas spp y una gram-positiva Enterococcus spp) y tres Contaminantes de Preocupación Emergente (CE) (Diclofenaco-DCF, Sulfametoxazol-SMX y Trimetoprim-TMP). La fotoactividad de ZnO modificado con Ce, Yb o Fe se evaluó a escala de laboratorio (200 mL), obteniendo buenas cinéticas de inactivación bacteriana y degradación de CE. El ZnO-Ce mostró el mejor rendimiento, no obstante, se descartó el escalado de este proceso tanto su aplicación directa, considerando su similar eficiencia en comparación con TiO2-P25 y por el alto coste del tratamiento, como en combinación con PMS, por la la liberación de Zn2+ al agua tratada. El uso directo de PMS como agente oxidante para el tratamiento de agua y UWW se ha demostrado en este estudio, aumentado su eficiencia al ser el sistema irradiado tanto con lámparas UV-C como con luz solar natural. Se han postulado diferentes mecanismos de inactivación y degradación de CE para cada tipo de irradiación: activación de PMS para generar radicales (con fotones UV-C) y la no activación o mecanismo de oxidación directo (con luz solar natural). La capacidad de los procesos PMS/Solar y PMS/UV-C se evaluó en UWW a escala de planta piloto en un Colector Parabólico Compuesto (10 L) y en una planta piloto de UV-C (80 L), respectivamente. El mejor rendimiento de tratamiento se alcanzó con una concentración de PMS de 1 mM en ambos casos, logrando una inactivación exitosa de todos los objetivos microbianos (incluyendo bacterias resistentes a antibióticos), sin observar recrecimiento bacteriano tras 48 h y eliminando de manera eficiente los CE. Por otro lado, la eliminación eficiente de genes de resistentes a antibióticos y productos de transformación se obtuvo con PMS/UV-C, mientras que éstos parámetros siguen siendo un reto a abordar en el caso del proceso PMS/Solar. En ningún caso se observó toxicidad del agua tratada para Aliivibrio fischeri, excluyendo un efecto nocivo para el medio ambiente receptor del efluente, y solo un leve efecto fitotóxico en el crecimiento de dos de las tres semillas analizadas (L. sativum y S. alba), indicando la idoneidad del efluente para su reutilización en riego. Finalmente, el análisis de costes demostró que este factor clave podría ser una barrera importante para la implementación del proceso PMS/Solar en plantas centralizadas de tratamiento de UWW. No obstante, su consideración como sistemas descentralizados asociados a pequeños volúmenes de agua en zonas con alta incidencia de radiación solar, ahorrando costes energéticos mediante el aprovechamiento de la luz solar, podría ser una opción real y asequible.[CA] El món s'enfronta a una profunda crisi associada a l'aigua i la reutilització d'aigües residuals urbanes (UWW), especialment en agricultura, es presenta com una possible solució per a abordar aquest problema. No obstant això, la reutilització s'ha de promoure dins d'uns límits mínims de qualitat de l'aigua, els quals poden aconseguir-se mitjançant la implementació d'eficients tractaments terciaris en les actuals plantes de tractament d'aigües residuals urbanes. En les últimes dècades, els Processos Avançats d'Oxidació (PAO), basats en la generació d'espècies reactives d'oxigen altament oxidants i no selectives, s'han plantejat com a alternativa als tractaments convencionals per a desinfecció i descontaminació d'aigua residual. L'objectiu general d'aquest estudi és, per tant, l'avaluació de nous POA per a desinfecció i descontaminació simultània d'aigua, investigant: (i) fotocatàlisi heterogènia solar amb ZnO modificat (Ce, Yb i Fe) i TiO2-P25 de referència, (ii) peroximonosulfat (PMS) baix radiació solar natural (PMS/Solar), (iii) POA basats en radical sulfat utilitzant PMS i radiació UV-C (PMS/UV-C) i (iv) combinació de ZnO modificat amb PMS com a estratègia de tractament. Els objectius biològics i químics analitzats en aquest estudi van ser: tres patògens d'impacte en salut humana (dos bacteris gram-negatius Escherichia coli, Pseudomonas spp i un gram-positiu Enterococcus spp) i tres Contaminants de Preocupació Emergent (CE) (Diclofenac-DCF, Sulfametoxazol-SMX i Trimetoprim-TMP). La fotoactivitat de ZnO modificat amb Ce, Yb o Fe es va avaluar a escala de laboratori (200 mL), obtenint bones cinètiques d'inactivació bacteriana i degradació de CE. El ZnO-Ce va mostrar el millor rendiment, no obstant això, es va descartar l'escalat d'aquest procés tant mitançant la seua aplicació directa o com en combinació amb PMS, considerant la seua similar eficiència en comparació amb TiO2-P25, l'alt cost del tractament i l'alliberament de Zn2+ a l'aigua tractada. L'ús directe de PMS com a agent oxidant per al tractament d'aigua i UWW s'ha demostrat en aquest estudi, augmentat la seua eficiència quan el sistema és irradiat tant amb llums UV-C com amb llum solar natural. S'han postulat diferents mecanismes d'inactivació i degradació de CE per a cada tipus d'irradiació: activació de PMS per a generar radicals (amb fotons UV-C) i la no activació o mecanisme d'oxidació directe (amb llum solar natural). La capacitat dels processos PMS/Solar i PMS/UV-C es va avaluar en UWW a escala de planta pilot en un Col·lector Parabòlic Compost (10 L) i en una planta pilot d'UV-C (80 L), respectivament. El millor rendiment de tractament es va aconseguir amb una concentració de PMS d'1 mm en tots dos casos, aconseguint una inactivació reeixida de tots els objectius microbians (incloent bacteris resistents a antibiòtics), sense observar recreixement bacterià després de 48 h i eliminant de manera eficient els CE. D'altra banda, l'eliminació eficient de gens de resistents a antibiòtics i productes de transformació es va obtindre amb PMS/UV-C, mentre que aquests paràmetres continuen sent un repte a abordar en el cas del procés PMS/Solar. En cap cas es va observar toxicitat a l'aigua tractada per a Aliivibrio fischeri, excloent un efecte nociu per al medi ambient receptor de l'efluent, i només un lleu efecte fitotòxic en el creixement de dos de les tres llavors analitzades (L. sativum i S. alba), indicant la idoneïtat de l'efluent per a la seua reutilització en reg. Finalment, l'anàlisi de costos va demostrar que aquest factor clau podria ser una barrera important per a la implementació del procés PMS/Solar en plantes centralitzades de tractament de UWW. No obstant això, la seua consideració com a sistemes descentralitzats associats a xicotets volums d'aigua en zones amb alta incidència de radiació solar, estalviant costos energètics mitjançant l'aprofitament de la llum solar, podria ser una opció real i assequible.[EN] It is well recognized that the world is facing a water crisis and the reuse of urban wastewater (UWW) in agriculture, has been gaining attention as a reliable solution to address this problem. It is mandatory to promote the safe water reuse and minimum water quality limits could be achieved by upgrading the Urban Wastewater Treatment Plants, through the addition of an efficient tertiary treatment. In the last decades, Advanced Oxidation Processes (AOPs), relying on the potential generation of highly oxidant, reactive and non-selective Reactive Oxygen Species (ROS), have been raised as alternative to conventional treatments for both water disinfection and decontamination. The general aim of this study is the assessment of novel AOPs for the simultaneous disinfection and decontamination of water, investigating (i) solar heterogeneous photocatalysis, involving modified ZnO with Ce, Yb and Fe and the benchmark TiO2-P25, (ii) peroxymonosulfate (PMS) under natural solar radiation (PMS/Solar), (iii) Sulfate radical-based AOPs (SR-AOPs) involving PMS and UV-C radiation (PMS/UV-C) and (iv) combination of the best-performing photocatalytic material with PMS (PMS/modified ZnO). The involved biological and chemical targets in this study were: three human health impact pathogens (two gram-negative bacteria Escherichia coli, Pseudomonas spp. and the gram-positive Enterococcus spp.) and three Contaminants of Emerging Concern (CECs, Diclofenac-DCF, Sulfamethoxazole-SMX and Trimethoprim-TMP). Photoactivity of modified ZnO with Ce, Yb or Fe was assessed in 200-mL vessel reactors, attaining good target's removal kinetic rates. Best performing material was ZnO-Ce, but its feasibility for a further up-scaling was discarded both as photocatalyst alone, considering the similar performances obtained, compared to TiO2-P25 and the high treatment cost, and in combination with PMS, due to the release of high amount of Zn2+. PMS alone has been proven to be an effective oxidant agent for water and UWW treatment, increasing its effectiveness when illuminated with photons from UV-C lamps and natural sunlight. Nevertheless, different inactivation and CECs degradation mechanisms have been postulated for each type of irradiation, and according to the activation of PMS (with UV-C photons) or non-activation (under natural sunlight). The capability of PMS/Solar and PMS/UV-C processes were evaluated in actual UWW at pilot plant scale in 10-L Compound Parabolic Collector and in 80L UV-C pilot plant, respectively. Optimal load of PMS was found to be 1 mM in both cases, achieving successful inactivation of natural occurring bacteria and their antibiotic resistant counterparts, without observing bacterial regrowth after 48h and efficiently eliminating CECs. Efficient removal of antibiotic resistant genes (ARGs) and transformation products (TPs) was obtained by PMS/UV-C, while their elimination is still a challenge to be addressed in PMS/Solar process. Reclaimed UWW obtained by both PMS/Solar and PMS/UV-C process showed no toxicity towards Aliivibrio fischeri, excluding a harmful effect towards the receiving aquatic environment after effluent discharge, and a very slightly phytotoxic effect for growth of two out of the three tested seeds (L. sativum and S. alba), indicating the suitability of this water for its subsequent reuse for agriculture. The analysis of the treatment cost revealed that this key factor could be an important barrier for implementation of PMS/Solar process in large centralized UWW treatment plants. Nevertheless, its consideration as decentralized systems associated to small volume of water in areas with a high solar radiation incidence, saving energy costs by using natural solar radiation, could be a real and affordable option.Berruti, I. (2022). Assessment of novel Advanced Oxidation Processes for the Simultaneous Disinfection and Decontamination of Water [Tesis doctoral]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/183052TESI

Molecular Photochemistry

There have been various comprehensive and stand-alone text books on the introduction to Molecular Photochemistry which provide crystal clear concepts on fundamental issues. This book entitled "Molecular Photochemistry - Various Aspects" presents various advanced topics that inherently utilizes those core concepts/techniques to various advanced fields of photochemistry and are generally not available. The purpose of publication of this book is actually an effort to bring many such important topics clubbed together. The goal of this book is to familiarize both research scholars and post graduate students with recent advancement in various fields related to Photochemistry. The book is broadly divided in five parts: the photochemistry I) in solution, II) of metal oxides, III) in biology, IV) the computational aspects and V) applications. Each part provides unique aspect of photochemistry. These exciting chapters clearly indicate that the future of photochemistry like in any other burgeoning field is more exciting than the past

Degradation of polycyclic aromatic hydrocarbons in water: Alternative treatments to conventional processes.

Nowadays, polycyclic aromatic hydrocarbons (PAHs) are a group of chemical substances that deserves a great attention. PAHs consist of two or more condensed benzene rings, bonded in linear, cluster or angular arrangements that are ubiquitous in the environment. Due to their low solubility and high affinity for particulate matter, PAHs are found in water in extreme low concentrations, in the range of ng L-1 or µg L-1. However, even at these ultra-trace or trace levels, they exhibit harmful effects on living beings and humans, especially when present as mixtures. That is the case of anthracene (AN), which has been reported as an acute phototoxic compound, and benzo[a]pyrene (BaP), which is a carcinogenic and mutagenic pollutant. Therefore, their presence in the environment and, specifically in aquatic resources must be monitored. For this purpose, the chromatographic behavior of AN and BaP was studied, and three models were found describing the identification of AN and BaP, the quantification of AN and that of BaP. The factors influencing each of the models or indexes were also optimized and a new and fast analytical method allowing the determination of the analytes of interest at ultra-trace concentrations in surface water samples was developed. In addition to monitor the target pollutants, they must be also eliminated from water because of the adverse health effects associated. However, conventional processes water treatment facilities are operating with are not efficient in tackling the problem of AN and BaP pollution in water. In this regard, the implementation of alternative treatments, including advanced oxidation processes (AOPs), provides a very attractive option. AOPs have demonstrated to be highly interesting technologies for water remediation, particularly the combination of ultraviolet radiation in the UV-C range (UV-C) and hydrogen peroxide (H2O2). This Thesis addresses the evaluation of the efficiency of the UV-C/H2O2 oxidation system to treat water sampled from a natural reservoir polluted with AN and BaP. For this purpose, initially, the removal profiles of AN and BaP were investigated, as well as the organic matter mineralization capacity of the oxidation system and the production of innocuous degradation by-products. The system allowed obtaining very positive results in terms of the degradation of the pollutants of interest and the organic matter mineralization, avoiding the production of dangerous reactive intermediates. Furthermore, after the application of this treatment process, a residual H2O2 was observed in the reaction solution, which can be used for additional microbial load removal. The residual H2O2 found within the bulk after the application of the oxidation treatment was analyzed using an analytical method proposed here. Moreover, the oxidation potential of the UV-C/H2O2 process was assessed for the inactivation of wild total coliforms naturally contained in the water of study and the results were compared with the findings obtained from other photochemical technologies based on sonochemical reactions. It was found that the technology achieving the highest microorganism elimination in the shortest time and with the lowest electrical costs results was the UV-C/H2O2 process. Nevertheless, in spite of that, it is worth noting that the implementation of the UV-C/H2O2 oxidation process still requires high electrical needs, which increases the operating costs of the process. Therefore, in order to reduce such as costs, a photovoltaic (PV) array was sized and installed for supplying the energy requirements of the selected water treatment system. The installed PV system allows for the use of renewable energy both in developing and non-developing countries. In this regard, the treatment of water to be drinkable was observed to be plausible in countries with lack of economical resources and in communities far from the electrical grid, which exist in a high number in countries such as Colombia. In the second stage of the research, and taking into account the necessity of having kinetic models for finding out the optimal operating conditions without the necessity of conducting extensive experimentation, a kinetic model for the performance of the UV-C/H2O2 oxidation process was constructed and validated using a model compound. The kinetic model allows calculating the optimal level of H2O2 for efficiently degrading the pollutant of interest, as well as the effective level of HO• to be maintained throughout the reaction time of the UV-C/H2O2 system for achieving an efficient pollutant degradation, contributing to save costs and time.Ingeniería, Industria y Construcció

Continuous photocatalytic fuel production over wide-bandgap metal oxides

La fotosíntesi artificial ha estat proposada com una de les possibles solucions als problemes energètics i de matèries primes d’origen químic per a fer front, de forma anticipada, a l’esgotament dels combustibles d’origen fòssil en un futur proper. Aquesta tesis doctoral tracta l’estudi de catalitzadors prometedors i el disseny de reactors per a realçar l’eficiència de reacció i entendre l’origen de l’activitat fotocatalítica. Un sistema de reacció en flux continu va ser dissenyat i construït per a estudiar el procés de fotoreducció del CO2 amb aigua i l’electròlisi fotocatalítica de l’aigua. L’activitat fotocatalítica d’òxids conductors de banda prohibida (bandgap) àmplia tals com, TiO2, Ta2O5, MTaO3 (M = Na, K), i Ga2O3 va ser avaluada mitjançant l’ús de dos tipus de reactors; més concretament, reactors en suspensió i en fase gas, respectivament. Làmpades de mercuri d’alta pressió van ser utilitzades coma fonts de llum. Els efectes dels co-catalitzadors (Pt i Rh-Cr) i dopant (Zn), en la formació de productes en la fase gas, va ser investigada. A partir de catalitzadors basats en TiO2, H2 i CH4 van ser detectats i quantificats. L’activitat va ser, pràcticament, de naturalesa transitòria (desactivació). Encara més important, aquest treball va elucidar que l’activitat podia ser recuperada en la foscor (sense irradiació) en la mescla de CO2 i H2O. El procés de recuperació va ser més eficient a altes temperatures. Estudis DRIFTS in situ van permetre millorar el coneixement en respecte al procés de recuperació sobre Pt/TiO2. Materials basats en òxids de Ta y Ga, co-modificats amb Zn i Rh-Cr, van exhibir una alta activitat global per al procés d’electròlisi de l’aigua, mentre que cap activitat per a la reducció de CO2 va ser observada. Tècniques fotofísiques van ser emprades per a identificar els rols clau de la promoció amb Zn i Rh-Cr en l’increment de l’activitat catalítica i la producció d’oxigen.La fotosíntesis artificial ha sido propuesta como una de las posibles soluciones a los problemas energéticos y de materias primas de origen químico para hacer frente, de forma anticipada, al agotamiento de los combustibles fósiles en un futuro cercano. Esta tesis doctoral trata el estudio de catalizadores prometedores y el diseño de reactores para realzar la eficiencia de reacción y entender el origen de la actividad fotocatalítica. Un sistema de reacción en flujo continuo fue diseñado y construido para estudiar la fotoreducción de CO2 con agua y la electrolisis fotocatalítica del agua. La actividad fotocatalítica de óxidos conductores de banda prohibida (bandgap) ancha tales como TiO2, Ta2O5, MTaO3 (M = Na, K), y Ga2O3 fue evaluada mediante el uso de dos tipos de reactores; más concretamente, reactores en suspensión y en fase gas, respectivamente. Lámparas de mercurio de alta presión fueron utilizadas como fuentes de luz. Los efectos de los co-catalizadores (Pt y Rh-Cr) y dopante (Zn) en la formación de productos en la fase gas fue investigada. A partir de catalizadores basados en TiO2, H2 y CH4 fueron detectados y cuantificados. La actividad fue, prácticamente, de naturaleza transitoria (desactivación). Aún más importante, este trabajo elucidó que la actividad podía ser recuperada en la oscuridad (sin irradiación) en la mezcla de CO2 y H2O. El proceso de recuperación fue más eficiente a altas temperaturas. Estudios DRIFTS in situ permitieron mejorar el conocimiento en respecto el proceso de recuperación sobre Pt/TiO2. Materiales basados en óxidos de Ta y Ga, co-modificados con Zn y Rh-Cr, exhibieron una alta actividad global para el proceso de electrolisis del agua, mientras que ninguna actividad para la reducción de CO2 fue observada. Técnicas fotofísicas fueron empleadas para identificar los roles clave de la promoción con Zn y Rh-Cr en el incremento de la actividad catalítica y la producción de oxígeno.Artificial photosynthesis has been proposed as one of the possible solutions to the energetic and chemical-feedstock problems to cope with the anticipated near future depletion of fossil fuel resources. This doctoral thesis deals with the study of promising catalysts and reactor designs to enhance the reaction efficiency and understand the origin of photocatalytic activity. A continuous flow reaction system was designed and constructed to study CO2 photoreduction with H2O and photocatalytic water splitting. Photocatalytic activity of wide-bandgap semiconductor oxides such as TiO2, Ta2O5, MTaO3 (M = Na, K), and Ga2O3 was evaluated by using two different reactors, namely slurry and gas phase reactors. High pressure mercury lamps were used as the light source. Effects of co-catalysts (Pt and Rh-Cr) and dopants (Zn) on gas phase products evolution were investigated. From TiO2-based catalysts, H2 and CH4 were detected and quantified. The activity was mostly of a transient nature (deactivating). Importantly this work elucidated that the activity could be recovered in the dark (without irradiation) in the mixture of CO2 and H2O. The recovery process was more efficient at higher temperatures. In situ DRIFTS study gained mechanistic insights into the recovery process over Pt/TiO2. Ta and Ga oxides-based materials, co-modified with Zn and Rh-Cr, exhibited high overall steady-state water splitting activity, whereas no CO2 reduction activity was observed. Photophysic techniques were used to identify the key roles of Zn and Ru-Cr promotion in boosting catalytic activity and oxygen production