Thesis advisor: Susanto Basu / The Great Recession is arguably the most important macroeconomic event of the last three decades. Prior to the collapse of national output during 2008 and 2009, the United States experienced a sustained period of good economic outcomes with only two mild and short recessions. In addition to the severity of the recession, several characteristics of this recession signify it as as a unique event in the recent economic history of the United States. Some of these unique features include the following: Large Increase in Uncertainty About the Future: The Great Recession and its subsequent slow recovery have been marked by a large increase in uncertainty about the future. Uncertainty, as measured by the VIX index of implied stock market volatility, peaked at the end of 2008 and has remained volatile over the past few years. Many economists and the financial press believe the large increase in uncertainty may have played a role in the Great Recession and subsequent slow recovery. For example, Kocherlakota (2010) states, ``I've been emphasizing uncertainties in the labor market. More generally, I believe that overall uncertainty is a large drag on the economic recovery.'' In addition, Nobel laureate economist Peter Diamond argues, ``What's critical right now is not the functioning of the labor market, but the limits on the demand for labor coming from the great caution on the side of both consumers and firms because of the great uncertainty of what's going to happen next.'' Zero Bound on Nominal Interest Rates: The Federal Reserve plays a key role in offsetting the negative impact of fluctuations in the economy. During normal times, the central bank typically lowers nominal short-term interest rates in response to declines in inflation and output. Since the end of 2008, however, the Federal Reserve has been unable to lower its nominal policy rate due to the zero lower bound on nominal interest rates. Prior to the Great Recession, the Federal Reserve had not encountered the zero lower bound in the modern post-war period. The zero lower bound represents a significant constraint monetary policy's ability to fully stabilize the economy. Unprecedented Use of Forward Guidance: Even though the Federal Reserve remains constrained by the zero lower bound, the monetary authority can still affect the economy through expectations about future nominal policy rates. By providing agents in the economy with forward guidance on the future path of policy rates, monetary policy can stimulate the economy even when current policy rates remain constrained. Throughout the Great Recession and the subsequent recovery, the Federal Reserve provided the economy with explicit statements about the future path of monetary policy. In particular, the central bank has discussed the timing and macroeconomic conditions necessary to begin raising its nominal policy rate. Using this policy tool, the Federal Reserve continues to respond to the state of the economy at the zero lower bound. Large Fiscal Expansion: During the Great Recession, the United States engaged in a very large program of government spending and tax reductions. The massive fiscal expansion was designed to raise national income and help mitigate the severe economic contraction. A common justification for the fiscal expansion is the reduced capacity of the monetary authority to stimulate the economy at the zero lower bound. Many economists argue that the benefits of increasing government spending are significantly higher when the monetary authority is constrained by the zero lower bound. The goal of this dissertation is to better understand how these various elements contributed to the macroeconomic outcomes during and after the Great Recession. In addition to understanding each of the elements above in isolation, a key component of this analysis focuses on the interaction between the above elements. A key unifying theme between all of the elements is the role in monetary policy. In modern models of the macroeconomy, the monetary authority is crucial in determining how a particular economic mechanism affects the macroeconomy. In the first and second chapters, I show that monetary policy plays a key role in offsetting the negative effects of increased uncertainty about the future. My third chapter highlights how assumptions about monetary policy can change the impact of various shocks and policy interventions. For example, suppose the fiscal authority wants to increase national output by increasing government spending. A key calculation in this situation is the fiscal multiplier, which is dollar increase in national income for each dollar of government spending. I show that fiscal multipliers are dramatically affected by the assumptions about monetary policy even if the monetary authority is constrained by the zero lower bound. The unique nature of the elements discussed above makes analyzing their contribution difficult using standard macroeconomic tools. The most popular method for analyzing dynamic, stochastic general equilibrium models of the macroeconomy relies on linearizing the model around its deterministic steady state and examining the local dynamics around that approximation. However, the nature of the unique elements above make it impossible to fully capture dynamics using local linearization methods. For example, the zero lower bound on nominal interest rates often occurs far from the deterministic steady state of the model. Therefore, linearization around the steady state cannot capture the dynamics associated with the zero lower bound. The overall goal of this dissertation is to use and develop tools in computational macroeconomics to help better understand the Great Recession. Each of the chapters outlined below examine at least one of the topics listed above and its impact in explaining the macroeconomics of the Great Recession. In particular, the essays highlight the role of the monetary authority in generating the observed macroeconomic outcomes over the past several years. Can increased uncertainty about the future cause a contraction in output and its components? In joint work with Susanto Basu, my first chapter examines the role of uncertainty shocks in a one-sector, representative-agent, dynamic, stochastic general-equilibrium model. When prices are flexible, uncertainty shocks are not capable of producing business-cycle comovements among key macroeconomic variables. With countercyclical markups through sticky prices, however, uncertainty shocks can generate fluctuations that are consistent with business cycles. Monetary policy usually plays a key role in offsetting the negative impact of uncertainty shocks. If the central bank is constrained by the zero lower bound, then monetary policy can no longer perform its usual stabilizing function and higher uncertainty has even more negative effects on the economy. We calibrate the size of uncertainty shocks using fluctuations in the VIX and find that increased uncertainty about the future may indeed have played a significant role in worsening the Great Recession, which is consistent with statements by policymakers, economists, and the financial press. In sole-authored work, the second chapter continues to explore the interactions between the zero lower bound and increased uncertainty about the future. From a positive perspective, the essay further shows why increased uncertainty about the future can reduce a central bank's ability to stabilize the economy. The inability to offset contractionary shocks at the zero lower bound endogenously generates downside risk for the economy. This increase in risk induces precautionary saving by households, which causes larger contractions in output and inflation and prolongs the zero lower bound episode. The essay also examines the normative implications of uncertainty and shows how monetary policy can attenuate the negative effects of higher uncertainty. When the economy faces significant uncertainty, optimal monetary policy implies further lowering real rates by committing to a higher price-level target. Under optimal policy, the monetary authority accepts higher inflation risk in the future to minimize downside risk when the economy hits the zero lower bound. In the face of large shocks, raising the central bank's inflation target can attenuate much of the downside risk posed by the zero lower bound. In my third chapter, I examine how assumptions about monetary policy affect the economy at the zero lower bound. Even when current policy rates are zero, I argue that assumptions regarding the future conduct of monetary policy are crucial in determining the effects of real fluctuations at the zero lower bound. Under standard Taylor (1993)-type policy rules, government spending multipliers are large, improvements in technology cause large contractions in output, and structural reforms that decrease firm market power are bad for the economy. However, these policy rules imply that the central bank stops responding to the economy at the zero lower bound. This assumption is inconsistent with recent statements and actions by monetary policymakers. If monetary policy endogenously responds to current economic conditions using expectations about future policy, then spending multipliers are much smaller and increases in technology and firm competitiveness remain expansionary. Thus, the model-implied benefits of higher government spending are highly sensitive to the specification of monetary policy. / Thesis (PhD) — Boston College, 2014. / Submitted to: Boston College. Graduate School of Arts and Sciences. / Discipline: Economics.

Thesis advisor: Peter Ireland / A significant theoretical literature suggests that the effects of open market operations and large scale asset purchases are limited when short-term interest rates are constrained by the zero-lower-bound (ZLB). This view is supported by a growing body of empirical evidence that points to the tepid response of the U.S. economy to extraordinary policy measures implemented by the Federal Reserve (Fed) during the past several years. In the first essay, Effective Monetary Policy at the Zero-Lower-Bound, I show that permanent open market operations (POMOs), defined as financial market interventions that permanently increase the supply of money, remain relevant at the ZLB and can increase output and inflation. Consequently, I argue that the limited success of Fed policy in recent years may be due in part to the fact that it failed to generate sufficient money creation to support economic recovery following the Great Recession. I then demonstrate that conducting POMOs at the ZLB may improve welfare when compared to a broad range of policy regimes, and conclude by conducting a robustness exercise to illustrate that money creation remains relevant at the ZLB when it is not necessarily permanent. With these results in hand, I explore the consequences of Fed QE more directly in a framework asset purchases are an independent instrument of monetary policy. In the second essay, Effective Quantitative Easing at the Zero-Lower-Bound, I show that the observed lack of transmission between U.S. monetary policy and output economic activity a consequence of the fact the Fed engaged in what I define as sterilized QE: temporary asset purchases that have a limited effect on the money supply. Conversely, I show that asset purchase programs geared towards generating sustained increases in the money supply may significantly attenuate output and inflation losses associated with adverse economic shocks and the ZLB constraint. Furthermore, these equilibrium outcomes may be achieved with a smaller volume of asset purchases. My results imply that Fed asset purchase programs designed to offset the observed declines in the U.S. money supply could have been a more effective and efficient means of providing economic stimulus during the recovery from the Great Recession. The third essay—which is joint work with Apollon Fragkiskos, Harold Spilker, and Russ Wermers— titled Buyout Gold: MIDAS Estimators and Private Equity, we develop a new approach to study private equity returns using a data set first introduced in Fragkiskos et al. (2017). Our innovation is that we adopt a mixed data sampling (MIDAS) framework and model quarterly private equity returns as a function of high frequency factor prices. This approach allows us to endogenize time aggregation and use within-period information that may be relevant to pricing private equity returns in a single, parsimonious framework. We find that our MIDAS framework offers superior performance in terms of generating economically meaningful factor loadings and in-sample and out-of-sample fit using index and vintage-level returns when compared with other methods from the literature. Results using fund-level data are mixed, but MIDAS does display a slight edge. Concerning appropriate time-aggregation, we show that there is significant heterogeneity at the vintage level. This implies highly aggregated private equity data may not properly reflect underlying performance in the cross section.

Esse trabalho foi motivado pela conjugação das necessidades do Laboratório de Ressonância Magnética Nuclear com as características técnicas do autor dessa dissertação. Havia a necessidade urgente no grupo da documentação e melhoria da instrumentação e do software de processamento dos dados já desenvolvidos para a realização de experimentos de Ressonância Magnética Nuclear em campo externo nulo. Ao longo do desenvolvimento desse trabalho, verificouse a necessidade de novos desenvolvimentos, a saber: o desenvolvimento de um software para processamento dos dados e o desenvolvimento da automação do aparato de controle da temperatura dos experimentos (4,2 a 400 K). A partir do software para processamento dos dados desenvolvido em Matlab, é possível processar facilmente o sinal para reconstrução do espectro. O processamento dos dados pode ser feito por duas vias: integrando o sinal no domínio do tempo ou integrando sua Transformada Fourier (FT). Deste modo, o tempo de processamento dos dados foi consideravelmente reduzido. A automação do aparato para o controle da temperatura permite uma interação mais amigável com o sistema do criostato. Finalmente, o espectrômetro de RMN foi utilizado para o estudo de ligas de FeV na fase sigma. Esses experimentos foram realizados de modo a se observar os espectros dos núcleos de 51V (10 - 100 MHz) e suas oscilações quadrupolares em função da concentração de Fe e da temperatura. Com esse estudo, podese confirmar que os espectros são relativos aos núcleos de 51V. As intensidades das cinco linhas observadas são coerentes com as populações de átomos de V em cada um dos cinco sítios (A, B, C, D e E) cristalográficos, assim como determinado por Difração de Nêutrons. O acoplamento quadrupolar medido foi de aproximadamente 312 KHz para todos os sítios estudados. / This work was motivated by the combination of the needs of the Nuclear Magnetic Resonance Laboratory with the technical features of the author of this dissertation. There was an urgent need in the group to document and improve the instrumentation and data processing software already developed to carry out the zero external magnetic field Nuclear Magnetic Resonance experiments. During the development of this work, it was verified the need for new developments, namely: development of software for data processing and development of automation of the apparatus used for the NMR experiments versus temperature. From the software developed for data processing, written in Matlab, it is easily possible processing the signal to reconstruct the spectrum. The data processing can be done in two ways: integrating the signal in the time domain or integrating its Fourier Transform. The processing time of the data was fast. The automation of the apparatus for controlling the temperature allows a more friendly interaction with the cryostat system. Finally, the NMR spectrometer was used to the study of FeV alloys in sigma phase. The experiments were performed to observe the 51V spectra (10 MHz to 100 MHz) and their quadrupolar oscillations, versus of the Fe concentration and temperature. With this study, it was possible to confirm that the spectra are relative to the 51V nuclei. The intensities of the five lines observed are coherent with the population of the V atoms in each of the Five crystallographic site (A, B, C, D e E), as determined by Neutron Diffraction. The quadrupolar couplings measured were found to be approximately 312 kHz for all sites studied.

We investigate quantum resonant transport in two different systems: (i) a ferromagnetic Scanning Tunneling Microscope (STM) tip coupled to an adatom (interacting) on a host surface (metallic or semiconductor), and (ii) a quantum dot connected to source and drain leads and side-coupled to a superconducting nanowire sustaining Majorana zero modes (Kitaev chain). Both problems are studied within the Green’s functions approach, which allows us to determine the transport properties of the system. In the first setup, due to the ferromagnetic and nonmagnetic ‘natures’ of the tip and host, respectively, it is possible to obtain the spin-diode effect, which occurs only in the singly occupied regime. In addition, because of the presence of the adsorbed atom on the surface, Friedel oscillations are observed in the current. The second system differs from the first mainly because it is spinless and there is no Coloumb interaction. Interestingly, we find that the Majorana mode of the wire leaks into the dot thus giving rise to a Majorana (zero mode) resonance in the dot, pinned to the Fermi level of the leads. Surprisingly, this resonance occurs even when the gate-controlled dot level is far above or far below the Fermi level of the leads. We study three possible experimental scenarios to probe unambigoulsy this Majorana mode in wires via these leaked/pinned modes. / Nesta tese investigamos transporte quântico ressonante em dois sistemas diferentes: (i) uma ponta STM ferromagnética acoplada a um átomo (interagente) adsorvido em uma superfície metálica ou semicondutora, e (ii) um ponto quântico conectado a reservatórios de elétrons e lateralmente acoplado a um nanofio supercondutor que possui modos de Majorana (cadeia Kitaev). Ambos os problemas são estudados no contexto de funções de Green, o que nos permite determinar as propriedades de transporte do sistema. Na primeira configuração, devido à natureza ferromagnética e não magnética da ponta STM e da superfície e, respectivamente, é possível obter o efeito diodo de spin, que ocorre apenas no regime em que o adátomo está ocupado com um único elétron. Além disso, por causa da presença do átomo adsorvido sobre a superfície, oscilções de Friedel são observadas na corrente. O segundo sistema é diferente do primeiro, principalmente pela ausência da interação de Coloumb e pelo fato de não ter spin. Curiosamente, vemos que o modo de Majorana do fio vai para o ponto quântico dando origem assim a um modo com energia zero no ponto quântico localizado sempre no nível de Fermi dos contatos. Surpreendentemente, essa ressonância ocorre mesmo quando o nível do ponto quântico, controlado por uma tensão externa, está muito acima ou muito abaixo do nível de Fermi dos contatos. Propomos três possíveis cenários experimentais para identificar de maneira conclusiva este modo de Majorana em fios através do modo que aparece no ponto quântico.

The fashion system is contributing to the environmental and social crises on an ever increasing scale. The industry must transform in order to situate itself within the environmental and social limits proposed by economist Kate Raworth, and the 17 sustainable development goals set out by the United Nations. This research explored methods of eliminating textile waste through utilising zero waste pattern cutting to expand the outcomes possible within industrial contexts and speculates as to the implications for the wider industry and society. Employing an experimental and phenomenological approach, this thesis outlines the testing of known strategies in the context of industry and responds with new emergent strategies to the challenges that arose. A series of interviews were conducted with designers who have applied zero-waste fashion design in an industry context – both large and small scale – to unpack the strategies used and contextualise the difficulties faced. The findings that emerged from the iterative design practice and the experience of working within the field tests inform the surrounding discussions and reflections. This reflection brings into sharp relief the inherent conflicts that exist within the fashion system and has led to the development of a series of theoretical models.The implications for design and industry are broad. Firstly that while this thesis outlines garment design strategies, and broader – company-wide – approaches that can work to reduce waste in a given context, this research finds that a holistic transformation of the internal design and management processes of the industry is required for them to be successful. In response, theoretical models have been developed which seek to articulate the constraints, roles and actions of design within broader company practices, while contextualising these within the economic system it operates. It is clear that reducing waste will only have a minor positive effect on the environmental outcomes unless we also reduce consumption of raw materials through reducing yield or reducing consumption – ideally both. These findings and models point towards a necessary recalibration of the industry as a whole – small changes are not enough as the existing methods, processes and ethos are deeply embedded, and its agents are resistant to change. The results concur with previous research and conclude that a fundamental shift in thinking is required – one that prioritises a different set of constraints to those the industry and society currently focus on – in order to make the rapid and meaningful change necessary.

In complex information flows where a lot of varied data is transmitted through many companies and divisions, incidents will occur. When Visma Spcs had an incident where invoices sent from Visma to Visma's customers were duplicated and the service meant to receive the transactions did not handle the duplicates properly. They decided that the receiver service was to be upgraded to prevent this incident from happening again, as well as fixing some other issues the service had had. Incidents like this one must be investigated and a solution must be implemented to decrease the likelihood that similar incidents will happen again. In this report, the reader will see examples on how this can be handled and the benefits of tackling technical debt, along with how much more complicated the solutions might get if the service is not allowed to be taken offline.

Neste trabalho é apresentado um estudo do ponto ZTC (Zero Temperature Coefficient) em dispositivos SOI MOSFETs, funcionando em modo parcialmente (PD-SOI) e totalmente (FD-SOI) depletados. O estudo é realizado a partir de um modelo analítico simples, proposto para determinação da tensão de polarização da porta do transistor no ponto ZTC (VZTC), através dos modelos de primeira ordem das características da corrente de dreno (IDS) em função da tensão aplicada a porta (VGF) do transistor, considerando as regiões de operação linear e de saturação. Para a validação do modelo, os resultados obtidos são confrontados com dados experimentais, e foi obtido um bom ajuste dos valores, apesar das simplificações adotadas para o modelo proposto. Foi realizada uma análise para estudar o impacto no valor de VZTC com a variação no valor de parâmetros de referência, como a concentração de portadores (Naf) e a espessura do óxido de porta (toxf). O erro máximo observado em VZTC, impondo a variação nos parâmetros Naf e toxf, para os dispositivos PD é de 3,1% e 4,6% na região linear, respectivamente; e 3,5% e 7,2% na região de saturação, respectivamente. Para os dispositivos FD o erro máximo observado, devido a variação nos parâmetros Naf e toxf, foi de 11% e 10% operando no regime linear, respectivamente e 5,3% e 8,4% no regime de saturação, respectivamente. Através do modelo proposto foi realizado o estudo da estabilidade do ponto ZTC em função da variação da degradação da mobilidade com a temperatura (fator c), comprimento de canal (L) e a tensão de dreno (VDS) para os dispositivos supracitados. A analise da influência do fator c em VZTC mostrou-se mais importante nos dispositivos parcialmente depletados (PD). A tensão VZTC, para os dispositivos nMOS, apresentou um menor valor operando na região de saturação, e torna-se mais pronunciada essa diferença para dispositivos com menor comprimento de canal, para ambos os tipos de dispositivos. Observando a variação de VZTC com VDS, nota-se uma diminuição no valor de VZTC para altos valores de VDS, para os dois tipos de dispositivos estudados, n e pMOS. Os resultados do modelo proposto foram avaliados com dados experimentais de outras tecnologias SOI MOSFET. Também foi obtido um bom ajuste com os valores para as tecnologias GC-SOI e GC-GAA SOI, operando em regime linear e saturação. / This paper presents a study of ZTC point (\"Zero Temperature Coefficient) in SOI MOSFETs devices, partially (PD-SOI) and fully (FD-SOI) depleted mode. The study is performed from a simple analytical model proposed for the determination of the gate bias voltage at ZTC point (VZTC) using the first-order models of the drain current (IDS) characteristics as a function of the gate voltage (VGF), operating in the linear and saturation regimes. To validate the model proposed results were compared with experimental data, and the analytical predictions are in very close agreement with experimental results in spite of the simplification used for the VZTC model proposed. Analysis was performed to study the impact on the VZTC value with the change in the parameters used as reference, such as Naf and toxf. The maximum error observed for the PD devices is 3.1% and 4.6% in the linear region and 3.5% and 7.2% in the saturation region, respectively. For FD devices the maximum error observed was 11% and 10% operating in the linear and 5.3% and 8.4% in the saturation regime. In order to verify the stability of the ZTC point as a function of the mobility degradation (c), channel length (L) and drain voltage (VDS), the proposed model was applied to the devices mentioned above. The VZTC changes in the temperature range investigated showed a temperature mobility degradation dependence and are more pronounced in PD devices. The VZTC voltage for nMOS devices presented a lower value operating in the saturation region than in the linear region, and this difference becomes more pronounced to devices with smaller channel length for both devices, n and pMOS. Analyzing the VZTC variation with drain voltage (VDS), showed a decrease in VZTC value for higher VDS, for both studied devices. The model proposed results were evaluated using experimental data from other SOI MOSFET technologies. And also we have obtained for the GC SOI and GC-GAA-SOI technologies a very close agreement, operating in both regions, linear and saturation.

The results section of my thesis includes three chapters. The first two chapters are on theoretical game theory. In both chapters, by mathematical modelling and game theoretical tools, I am predicting the behaviour of the players in some real world issues. Hoteling-Downs model plays an important role in the modern political interpretations. The first chapter of this study investigates an extension of Hoteling-Downs model to have multi-dimensional strategy space and asymmetric candidates. Chapter 3 looks into the inspection game where the inspections are not the same in the series of sequential inspections. By modelling the game as a series of recursive zero-sum games I find the optimal strategy of the players in the equilibrium. The forth chapter investigates direct optimization methods for large scale problems. Using Matlab implementations of Genetic and Nelder-Mead algorithms, I compare the efficiency and accuracy of the most famous direct optimization methods for unconstraint optimization problems based on differing number of variables.

In this Thesis either advanced oxidation or reductive processes are investigated for the degradation of two pesticides considered persistent in the environment: amicarbazone (AMZ) and chlorpyrifos (CP). In chapter I, different advanced oxidation processes (AOPs) driven by sulfate (SO4o-) and hydroxyl radicals (oOH) were applied to the degradation of AMZ. In the first study, several persulfate (PS) activated reactions were explored for AMZ degradation, namely activation with UVA radiation, Fe(II) and H2O2, as well as the combination of UVA radiation with Fe(II), Fe(III) and Fe(III)-complexes. Here, the influence of different reaction variables, such as solution pH, reactants and pesticide initial concentrations, addition of a second oxidant (H2O2) and the addition of different iron catalysts were also investigated. Control experiments regarding the photolysis of iron species in the absence of PS captured our interest and, with the aim of exploring more deeply this process on AMZ degradation, a second investigation was carried out. In this second study, a Doehlert experimental design was applied to investigate the simultaneous effects of two variables on AMZ degradation: pH and Fe(III):carboxylate ratio, where the carboxylate could be oxalate, citrate or tartrate. A response surface model for the observed degradation rate (kobs) as a function of pH and Fe(III):carboxylate ratio was obtained. The processes explored in both aforementioned studies revealed to be effective for AMZ removal, although nothing is known yet about their effectiveness regarding toxicity removal. Given that, a third study was carried out, where the toxicity of AMZ solutions, before and after submission to the processes studied was evaluated towards five microorganisms: Vibrio fischeri (acute toxicity), Tetrahymena thermophile, Chlorella vulgaris (chronic toxicity), Escherichia coli and Bacilus subtilis (antimicrobial activity). The last investigation detailed in chapter I is related with the application of zero-valent-metals on PS activation, which is a subject that links this chapter with the following one. For that, zero-valent-iron (ZVI) was investigated as a PS activator and the influence of variables that help to assess the environmental applicability of this process. In general, organochlorine pesticides reveal a higher resistance to oxidation than reduction, the latter process preferred when the aim is to degrade that important class of contaminants. Therefore, in chapter II the reductive degradation of CP by means of zero-valent-metals and bimetallic particles was investigated. ZVI has been extensively applied for that purpose. However, besides iron, other zero-valent metals can be potential reactive materials for reductive degradation and hence, in this study, the effectiveness of Zn0 and Cu0 was also explored in comparison to that widely reported for ZVI. Furthermore, two different ways of enhancing metals reactivity were here explored: i) by coating ZVI or Zn0 with a more noble metal (Cu), in order to analyze the copper catalytic effect on the bimetallic system; ii) by different surface pretreatments. / Na presente Tese de Doutorado foram abordados tanto processos oxidativos avançados (POA), como processos redutivos por metais de valência zero, na degradação de dois pesticidas considerados persistentes no meio ambiente: amicarbazona (AMZ) e clorpirifós (CP). No capítulo I são apresentados os estudos realizados com diversos POA, mediados por radicais sulfato (SO4o-) e hidroxila (oOH), aplicados da AMZ. Num primeiro estudo foi explorada a ativação do oxidante persulfato (PS), de diferentes formas, tais como radiação UVA, H2O2 e Fe(II), assim como a combinação de radiação UVA com Fe(II), Fe(III) e complexos de Fe(III). Aqui também foram investigados os efeitos de diversas variáveis reacionais, tais como pH, concentração inicial de reagentes e de pesticida, adição de um segundo oxidante (H2O2) e adição de diferentes espécies de ferro. Os testes realizados, para efeito de controle, referentes à irradiação das espécies de Fe(III) na ausência de PS, despertaram o interesse para um estudo mais aprofundado sobre o efeito da fotólise destas espécies na degradação da AMZ, surgindo assim o segundo trabalho. Neste utilizou-se um projeto experimental de Doehlert, para avaliar o efeito de duas variáveis em simultâneo quanto à degradação da AMZ: pH e proporção Fe(III): ligante, sendo o ligante um dos seguintes carboxilatos: oxalato, citrato ou tartarato. Um modelo de superfície de resposta, que correlaciona a taxa de degradação observada (kobs) em função do pH e proporção Fe(III):ligante foi obtido para cada um dos complexos de Fe(III) estudados. Os processos explorados, tanto no primeiro como no segundo estudo, se mostraram eficazes na remoção da AMZ, porém nada se sabe acerca da remoção da toxicidade. Para tal, foi desenvolvido um terceiro estudo dedicado à avaliação da toxicidade da solução de AMZ, antes e após a aplicação de cada um dos processos anteriormente abordados, contra cinco micro-organismos: Vibrio fischeri (toxicidade aguda); Tetrahymena thermophila, Chlorella vulgaris (toxicidade crônica); Escherichia coli e Bacilus subtilis (atividade antimicrobiana). O último estudo abordado no capitulo I é referente à aplicação de metais de valência zero também nos POA, correlacionado assim o capítulo I e o capítulo II. Como tal, foi feito um estudo de ativação de PS por meio de ferro de valência zero (Fe0), em que se investigou a influência de diversas variáveis por forma a inferir sobre a aplicabilidade prática deste processo. Pesticidas organoclorados apresentam maior resistência à degradação por processos oxidativos do que redutivos, sendo preferível o último na degradação desta importante classe de contaminantes. Como tal, o capítulo II se refere à degradação redutiva, por meio de diferentes metais de valência zero e partículas bimetálicas, do pesticida organoclorado CP. Além do amplamente explorado Fe0, outros metais podem ser aplicados neste processo, pelo que, neste estudo, explorou-se a potencialidade de Zn0 e Cu0 comparativamente ao primeiro. Ainda neste estudo foram investigadas duas formas de aumentar a reatividade dos metais: i) no caso do Fe0 e Zn0, revestindo com um metal mais nobre (Cu), por forma a observar o efeito catalisador do último no sistema bimetálico; ii) realizando um pré-tratamento à superfície dos metais.

Atualmente, um dos tópicos mais relevantes da Química Ambiental é a qualidade da água. A preocupação com micropoluentes, poluentes que estão presentes no meio ambiente em con-centrações de μg L-1 a ng L-1, tem aumentado recentemente. O objetivo deste trabalho foi estudar a degradação de antibióticos de duas classes: norfloxacina (fluoroquinolona), sulfati-azol e sulfametazina (sulfonamidas) e o anti-inflamatório não esteroide diclofenaco de sódio pelo acoplamento do Processo Ferro Zero, com nanopartículas de Fe0 ou lã de aço comercial, ao Processo Fenton. Teve-se como metas a identificação de produtos de degradação, a avali-ação da ecotoxicidade (Lactuca sativa) e da atividade antimicrobiana (Escherichia coli). Os experimentos de degradação foram realizados via planejamento fatorial 22 com a finalidade de se determinar os efeitos dos parâmetros reacionais (pH e vazão) sobre o desempenho do Processo Ferro Zero. As partículas de Fe0 sintetizadas foram nanométricas (< 100 nm), verificou-se a sua morfologia esférica e constatou-se a presença de Fe0, óxidos de ferro e hidróxidos de ferro. O Processo Ferro Zero em meio óxico, utilizando as NPFe0 ou a lã de aço comercial, obteve remoções de 31,5 ± 1,5% ou 51,9 ± 3,9%, respectivamente. Ao se realizar o Processo Ferro Zero em meio anóxico, observou-se que a degradação redutiva foi mais eficiente que a oxidativa, removendo-se aproximadamente 51,4 ± 2,3% ou 59,6 ± 1,9% com nanopartículas de Fe0 ou lã de aço comercial, respectivamente. Para o sulfatiazol obtiveram-se remoções de 77,7 ± 1,9% ou 73,4 ± 3,2%, para a sulfametazina remoções de 54,8 ± 2,7% ou 50,6 ± 2,8% e, para a norfloxacina, 68,9 ± 2,2% ou 67,2 ± 2,0%, quando se utilizaram as nanopartículas de ferro metálico ou a lã de aço comercial, respectivamente. Todos os processos não geraram ecotoxicidade ao organismo-teste (Lactuva sativa). Entretanto, as nanopartículas de Fe0 foram mais eficientes na remoção da atividade antimicrobiana (Escherichia coli) e produziram menores concentrações de ferro dissolvido ao final do tratamento, sendo mais indicadas para a degradação da norfloxacina. O uso das nanopartículas de ferro foi capaz de, praticamente, remover a atividade antimicrobiana da norfloxacina. / Presently, one of the most relevant topics in environmental chemistry is water quality. The concern with micropollutants, which are pollutants present in the environment in concentra-tions ranging from μg L-1 to ng L-1, has recently increased. The objective of this work was to study the degradation of the antibiotics: norfloxacin (fluoroquinolone), sulfathiazole, and sulfamethazine (sulfonamides) and the nonsteroidal anti-inflammatory sodium diclofenac by coupling Zero-Valent Iron (with Fe0 nanoparticles or commercial steel wool) and Fenton pro-cesses. The study aimed at identifying degradation products and assessing ecotoxicity (Lactuca sativa) and antimicrobial activity (Escherichia coli). The degradation experiments followed a factorial design 22 in order to determine the effects of the reaction parameters (pH and flow rate) on the performance of the Zero-Valent Iron process. Iron nanoparticles were synthesized (< 100 nm), their spherical morphology checked, and the presence of Fe0, iron oxides, and iron hydroxide confirmed. The Zero-Valent Iron process in oxic media, using NPFe0 or commercial steel wool, obtained removals of 31.5 ± 1.5% or 51.9 ± 3.9%, respec-tively. Using the Zero-Valent Iron process in anoxic medium, it was observed that the reduc-tive degradation was more efficient than the oxidative one, removing approximately 51.4 ± 2.3% and 59.6 ± 1.9% when using Fe0 nanoparticles and commercial steel wool, respectively. For sulfathiazole, sulfamethazine, and norfloxacin, removals of 77.7 ± 1.9% or 73.4 ± 3.2%, 54.8 ± 2.7% or 50.6 ± 2.8%, and 68.9 ± 2.2% or 67.2 ± 2.0% were obtained when Fe0 nano-particles or commercial steel wool trade were used, respectively. All of the processes did not generate ecotoxicity towards the test-organism (Lactuva sativa). However, the Fe0 nanoparti-cles were more effective in removing the antimicrobial activity (Escherichia coli) and pro-duced lower concentrations of dissolved iron at the end of the treatment, being more suitable for degrading norfloxacin. The use of the iron nanoparticles was able to virtually remove the antimicrobial activity of norfloxacin.