Photocatalytic Degradation of Phenolic Compounds in Water: Irradiation and Kinetic Modeling

Scaling up a photoreactor requires both knowledge of optical properties of the slurry medium and an established kinetic model. Measuring the scattering and absorption coefficients of particles suspended in water involves the use of specialized optical equipment, as well as the partial solution of the radiative transfer equation (RTE). In addition, modeling of the radiation field in photoreactors with complicated geometries offers special challenges. On the other hand, most of the kinetic models (KM) for phenol photodegradation reported in the literature were obtained for a single organic chemical species only. In fact, neglecting all the intermediate species generated during the photoreaction, is a common oversimplification that limits the KM application. As a result, once the radiation and kinetic models fully established, energy efficiencies can be obtained. In this PhD dissertation, the photocatalytic degradation of phenol over four different TiO2 catalysts is studied. It is proven that phenol yields hydroquinone, catechol, benzoquinone, and acetic and formic acids as main intermediate species. The radiation field inside photocatalytic reactors is predicted by solving the RTE. From the solution of the RTE, the local volumetric rate of energy absorption (LVREA) is also calculated. The radiation field inside an annular photoreactor is simulated using the Monte Carlo (MC) method for different TiO2 suspensions in water. All simulations are performed by using both the spectral distribution, and the wavelength-averaged scattering and absorption coefficients. The Henyey-Greenstein phase function is adopted to represent forward, isotropic and backward scattering modes. It is assumed that the UV lamp reflects the back-scattered photons by the slurried medium. It is proven, photo-absorption rates, using MC simulations and spectral distribution of the optical coefficients, agree closely with experimental observations from a macroscopic balance (MB). It is also found that the scattering mode of the probability density function, is not a critical factor for a consistent representation of the radiation field. When solving the RTE, two optical parameters are needed: (1) the absorption and scattering coefficients, and (2) the phase function. In this research work, the MC method, along with an optimization technique, is shown to be effective in predicting the wavelength-averaged absorption and scattering coefficients for different TiO2 powders. To accomplish this, the LVREA and the transmitted radiation (Pt) in the photoreactor are determined by using a MB. The optimized coefficients are calculated ensuring that they comply with a number of physical constrains, falling in between bounds established via independent criteria. The optimization technique is demonstrated by finding the absorption and scattering coefficients for different semiconductors that best fit the experimental values from the MB. The objective function in this optimization is given by the least-squared error for the LVREA. A photocatalyst is synthesized and its optical properties determined by the proposed method. This approach is a general and promising one; not being restricted to reactors of concentric geometry, specific semiconductors and/or particular photocatalytic reactor unit scale. Based on the proposed intermediate reactions, a phenomenological based unified kinetic model is proposed for describing the obtained experimental observations in phenol photodegradation. This Langmuir-Hinshelwood (L-H) kinetic model is based on a “Series-Parallel” reaction network. This reaction model is found to be applicable to the various TiO2 photocatalyst in the present study. This unified kinetic network is based on the identified and quantified chemical species in the photoconversion of phenol and its intermediates. In order to minimize the number of optimized parameters, the adsorption constants of the different intermediate species on the different catalysts configuration, are obtained experimentally. It is shown that the unified kinetic model requires a number of significant assumptions to be effective; avoiding overparametization. As a result, the unified kinetic model is adapted for each specific TiO2 photocatalyst under study.These different models adequately describe the experimental results. It is shown that this approach results in good and objective parameter estimates in the L-H kinetic model, which is typically applied to photocatalytic reactors. Finally, two efficiency factors, the quantum yield and the photochemical and thermodynamic efficiency factor, are obtained, in this PhD dissertation. These factors are based on the kinetic model proposed and the radiation being absorbed by the photocatalyst particles. The efficiency calculations consider stoichiometric relationships involving observable chemical species and OH· groups. The obtained efficiency factors point toward a high degree of photon utilization and, as a result, the value of photocatalysis and Photo-CREC-Water reactors for the conversion of organic pollutants in water is confirmed

Comunicação do risco natural em Portugal

Na presente dissertação pretende-se compreender como é que a comunicação do risco é considerada pelos profissionais ligados à gestão do risco no domínio das calamidades naturais em Portugal. Para tal, além da fundamentação teórica acerca do objeto de estudo deste trabalho, ou seja, da comunicação do risco, pretende-se reunir algumas pistas que permitam compreender a visão que os profissionais ligados à gestão do risco, nomeadamente no âmbito das calamidades naturais têm desta disciplina de comunicação. É igualmente propósito desta dissertação aferir se a sociedade civil tem acesso a informação no que concerne a comportamentos redutores do risco no domínio da ocorrência de uma catástrofe natural, tais como um sismo ou um tornado. Neste sentido, pretende-se, portanto clarificar, em primeiro lugar, se existem, de facto, esforços de comunicação no que diz respeito à divulgação de informação sobre os riscos inerentes a um determinado fenómeno natural. E, segundo compreender o motivo pelo qual a sociedade civil portuguesa não tem um papel ativo no processo de gestão do risco: será que esta inércia se deve à falta de interesse (aliada à ignorância) da população no que concerne a temática do risco, em particular, no domínio da ocorrência de catástrofes naturais. Por fim, na presente dissertação é apresentado um guia de boas práticas para porta-vozes no domínio da comunicação do risco.ABSTRACT: The present Master final work aims to understand how risk communication is considered by professionals involved in risk management in the field of natural disasters in Portugal. To this end, besides the theoretical background about the object of study of this work, is intended to bring together some clues in order to understand the vision about this communication’ s discipline sustained by the professionals involved in risk management, particularly in the context of natural disasters. It is also a purpose of this dissertation assessing whether civil society has access to information concerning the conduct of reducing risk in the area of occurrence of a natural disaster such as an earthquake or a tornado. In this sense, the aim is therefore to clarify, first, whether there are, in fact, communication efforts regarding the disclosure of information about the risks inherent in a particular natural phenomenon. And, second, to understand why the Portuguese civil society has not an active role in the process of risk management: is this inertia due to lack of interest (along with ignorance) of the population regarding the issue of risk particularly in the field of natural disasters. Finally, in this Master final work is presented a good practices guide for spokespersons in the field of risk communication

Contexts for questioning: Two zones of teaching and learning in undergraduate science

This is the author's accepted manuscript. The final published article is available from the link below. Copyright @ Springer Science+Business Media B.V. 2012.Higher education institutions are currently undertaking a challenging process in moving from teacher-orientated to student-focused approaches. Students’ ability to asking questions is fundamental to developing critical reasoning, and to the process of scientific enquiry itself. Our premise is that questioning competences should become a central focus of current reforms in higher education. This study, part of a broader naturalistic research project, aims at developing a theoretical framework for conceptualizing different contexts for questioning, illustrating the application of the proposed framework (contextual questioning zones) and reflecting about some of the dimensions of teaching and learning, for overcoming some of the challenges that higher education institutions are facing presently. The discussion of two ‘opposite’ contexts of enquiry is based on qualitative data, gathered through close collaboration with four teachers of undergraduate biology at a Portuguese university. These teachers were observed during their ‘daily activity’ during an academic year. Data was also gathered by interviewing these teachers and 8 selected students, at the end of the year, and used to sustain the argumentation. The paper concludes with some reflections and suggestions to promote authentic enquiry-based learning experiences.Portuguese Fundação para a Ciência e a Tecnologi

Ecological, anatomical and physiological traits of benthic macroinvertebrates : their use on the health characterization of freshwater ecosystems

After some studies made in Northern Portuguese freshwater ecosystems using the benthic macroinvertebrate communities for water quality evaluation, it has been possible to see that only the analysis of some characteristics allowed to distinguish different levels of environmental disturbance. The studies of some characteristics of the macroinvertebrates and the comparison with the results of the physico-chemical parameters analysed show that the more disturbed the ecosystems had, the lower dissolved oxygen concentration and organisms with greater independence from this concentration. The objective of this work is to define groups of organisms, attending to some of their characteristics that are related to getting oxygen. The groups were defined through bibliographic information and from direct observation of their behaviour. The ability of these groups to distinguish different types of ecosystems was analysed by comparison of the obtained results on their distribution in a group of sampling sites located along gradients of contamination, with the results obtained by the calculation of biological indices, descriptive metric analyses of the community, and the water chemical quality. After this study, it is possible to say that the results obtained with the use of respiratory groups can be more informative than that obtained with the analysis of the physico-chemical parameters or other biological parameters.Tras diversos estudios efectuados en ecosistemas acuáticos del Norte de Portugal usando las comunidades de macroinvertebrados para evaluar la calidad del agua ha sido posible verificar que solo el estudio de algunas características permitía diferenciar niveles de perturbación ambiental. El estudio de algunas características de los macroinvertebrados y la comparación con los resultados de los parámetros físico-químicos analizados ha mostrado que cuanto más perturbados eran los sistemas, menor era la concentración de oxigeno disuelto y más independientes de su concentración los organismos presentes. El objetivo de este trabajo es definir grupos de organismos, atendiendo a algunas de sus características relacionadas con la obtención de oxigeno. Los grupos fueran definidos a través de información de bibliografía y de la observación directa de su comportamiento. La capacidad de los grupos para distinguir los diferentes tipos de ecosistemas fue analizada través la comparación de los resultados obtenidos de su distribución en un conjunto de puntos de muestreo ubicados a lo largo de gradientes de contaminación con resultados obtenidos por el cálculo de índices biológicos, análisis métricos descriptivos de la comunidad y de la calidad química del agua. Al final de este estudio es posible decir que los resultados obtenidos con los grupos respiratorios pueden ser más informativos que los obtenidos con el análisis de los parámetros físico y químicos o con otros parámetros biológico

Eco-physiological characterization of the macroinverterbate communities of an urban stream (Rio Tinto, Portugal)

The Water Framework Directive ( DQA-2000/60/EC ) establishes as its main objective the achievement of a good ecological quality of all inland surface waters and groundwater by 2015 , and introduces the concept of " ecological status " of an ecosystem , which includes the study of a wide range of parameters and factors for determining the " health " system ". This work, carried out within a project which main objective is the rehabilitation of a small watercourse in high degree of ecological degradation, aims to make the study of benthic macroinvertebrate communities and some parameters related to the ecological state of Rio Tinto (Douro watershed) in order to determine the main sources of pollution and to propose measures for its rehabilitation. This study compare results (metrics and functional structure) of samples of the benthic macroinvertebrate communities collected at 10 sampling sites along the river in 2013/14 and values of some hydro-morphological, physical and chemical parameters. The results indicate that it is a water course which presents a high degree of degradation due to problems with artificiality of the channel and receipt of domestic and industrial effluents.LIPORN/

Burnout and suicidal behaviours in health professionals in Portugal: The moderating effect of self-esteem

The main objective of this study was to investigate the effect of burnout on suicidal behaviours and the mediating effect of self-esteem in this relationship. A total of 1172 healthcare professionals working in Portugal’s private and public sector organisations participated in this study. The results indicate a high level of burnout among these professionals and that exhaustion (β = 0.16; p < 0.001) and disengagement (β = 0.24; p < 0.001) positively and significantly affect suicidal behaviours. In turn, self-esteem has a significant and negative effect (β = −0.51; p < 0.001) on suicidal behaviours. Self-esteem moderates the relationship between disengagement and suicidal behaviours (B = −0.12; p < 0.001) and the relationship between exhaustion and suicidal behaviours (B = −0.11; p < 0.001), representing an essential variable for future lines of research, namely on the role of self-esteem in preventing burnout and suicidal behaviours in professionals from other professional areas.info:eu-repo/semantics/publishedVersio

Evolución de la percepción sobre los valores cívicos de los ciudadanos mexicanos durante el siglo XXI

El propósito de esta sección es que los lectores identifiquen el concepto y tipos de la cultura política, su relación con la cultura política democrática y la forma de arraigar y fortalecer la cultura democrática. Cultura política es un término de uso muy extendido. Se le emplea de manera genérica y coloquial para referir un conjunto de actitudes, ideas, reacciones o comportamientos sociales frente a fenómenos políticos. Pero la amplia difusión del término no ha implicado una mejor comprensión de su significado.Definido a grandes rasgos, el objetivo general del trabajo es explicar el papel y la importancia de la cultura política democrática como un elemento que puede ayudar a fortalecer el régimen democrático y modelar las conductas y estrategias de autoridades, partidos políticos y ciudadanos. Subyace a este planteamiento la idea que “el vigor y la estabilidad de una democracia moderna no dependen solamente de la justicia de su estructura básica, sino también de las cualidades y actitudes de sus ciudadanos” (Kymlicka y Norman, 1997: 6; cfr. Welzel e Inglehart, 2009). En ese sentido, no importan solo las instituciones, el tipo de gobierno o el sistema de partidos, sino además una cultura política democrática, la cual deviene en una condición favorable para la estabilidad, desarrollo y calidad de la democracia. Este trabajo explica las características conceptuales de la cultura democrática desde la literatura especializada. La exposición del tema está integrada por dos secciones que ofrecen un panorama general que va de la revisión teórica al caso mexicano. Según esta estructura, en la primera sección se desarrollan los elementos conceptuales de la cultura política, los tipos que proponen algunos especialistas, su relación con la cultura democrática y los componentes de esta última. Se muestra además cómo desarrollar y fortalecer la democracia a partir de los valores de la cultura política democrática

Common environmental descriptors of two benthic amphi-atlantic mollusc assemblages

Duas associações de moluscos bênticos litorais foram estudadas em ambos os lados do oceano Atlântico, uma tropical no Rio de Janeiro, Brasil, e outra temperada na Galicia, Espanha, procurando-se por descritores ambientais comuns, a ambas, que pudessem explicar, em macro escala, o porquê de essas associações estarem onde estão. As duas associações apresentam, aproximadamente, a mesma riqueza de espécies, cerca de 150 táxons cada uma. Ambas as faunas malacológicas habitam sedimentos arenosos em profundidades variando entre 2-12 m, na Galicia, e 10-40 m, no Rio de Janeiro. As associações malacológicas foram definidas através de Análise de Grupamento e caracterizadas ambientalmente com a aplicação da Análise Discriminante Múltipla realizada sobre os dados abióticos. Não existem espécies em comum entre as associações estudadas; contudo estes táxons apresentam caracteres fenológicos similares em função de habitarem as mesmas fácies sedimentológicas. Um mesmo conjunto de variáveis ambientais (tamanho médio do grão do sedimento, assimetria, curtose, grau de selecionamento, frações de areias fina e média e a profundidade) foram identificadas por condicionarem a presença dessas associações, sugerindo que possam ter um papel relevante como descritores ambientais gerais.Two benthic mollusc assemblages of the continental shelf on both sides of the Atlantic Ocean, a tropical one in Rio de Janeiro, Brazil, and another, temperate, in Galicia, Spain were investigated, with a view to finding common environmental descriptors which would explain, on a macro-scale, why these assemblages are there. Both of the assemblages concerned show approximately the same species richness, about 150 taxa each. The molluscan fauna of both regions live on sandy sediments. The Galician assemblages are at about 2-12 m depth, while those in Rio de Janeiro are at about 10-40 m depth. Malacological assemblages were defined through Cluster Analysis and Multiple Discriminant Analysis of the environmental data showed that each assemblage has its own environmental space. These assemblages have no species in common, but show the same phenological characters associated with each sedimentological facies. The same set of environmental variables (median sediment grain size, skewness, kurtosis, sorting, fine and medium sand fractions and depth) were selected as controlling these assemblages, suggesting that they play their role as general environmental descriptors