• Refine Query
  • Source
  • Publication year
  • to
  • Language
  • 638
  • 276
  • 107
  • 85
  • 66
  • 44
  • 31
  • 14
  • 12
  • 11
  • 9
  • 5
  • 5
  • 4
  • 4
  • Tagged with
  • 1543
  • 145
  • 135
  • 98
  • 91
  • 89
  • 84
  • 79
  • 79
  • 79
  • 76
  • 75
  • 72
  • 70
  • 69
  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
391

Edição de fotografia no jornal Zero Hora: entre a produção, a recepção e o produto

Moraes, Cybeli Almeida 26 March 2007 (has links)
Made available in DSpace on 2015-03-05T18:23:09Z (GMT). No. of bitstreams: 0 Previous issue date: 26 / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior / O presente trabalho pretende discutir a edição de fotografia do jornal diário Zero Hora, abordando a produção, a recepção e o produto fotojornalístico como as três instâncias que nos permitem compreender este processo. A partir de um estudo quanti-qualitativo sobre a fotografia na mídia impressa - e também dos aportes em torno dos processos de sentido, das teorias do jornalismo e dos estudos audiovisuais -, a presente pesquisa pretende identificar os “elementos definidores” da natureza e das lógicas do uso da fotografia em Zero Hora, estruturando-se em torno da “crítica” da imagem realizada no box Foto comentada. A partir deste micro-espaço de tensionamento entre foto, edição fotográfica, leitor e jornal, pretende-se perceber para quais direções, no âmbito do sistema fotojornalístico, estas discussões apontam. Entre os movimentos metodológicos realizados, estão as incursões nos campos da recepção e da produção (por meio de entrevistas, observação participante e observação do box Foto comentada), e também a análise de 172 fotografias publicadas em Zero Hora durante o ano de 2005. Como principais aportes teóricos, podemos citar os autores Jorge Pedro Sousa, Susan Sontag, Donis A. Dondis, Nélson Traquina, Mauro Wolf, Roland Barthes, Vilém Flusser, Pepe Baeza, Henri Bergson, Suzana Kilpp e José Luiz Braga, entre outros. / The present essay intends to discuss the photography edition of the Zero Hora daily newspaper, approaching the production, the reception and the photojournalistic product as the three instances that allow us to understand this process. Starting from a quanti-qualitative study on the photography in the media printed - and also of the contributions around the sense processes, the journalism theories and the audiovisual studies -, the present research intends to identify the “definer elements” of the nature and logics of the use of the photography in Zero Hora, being structured around the “critic” of the image accomplished in the box Foto comentada. Starting from this tensive space among photography, photographic edition, reader and newspaper, intends to notice for which directions, in the extent of the photojournalistic system, these discussions appear. Among the accomplished methodological movements, are the incursions in the reception and production fields (through interviews, participant observation and observation of the box Foto comentada), and also the analysis of 172 photographs published in Zero Hora during the year of 2005. As main theoretical contributions, we can mention authors Jorge Pedro Sousa, Susan Sontag, Donis A. Dondis, Nélson Traquina, Mauro Wolf, Roland Barthes, Vilém Flusser, Pepe Baeza, Henri Bergson, Suzana Kilpp and José Luiz Braga, among others.
392

De leitores a conselheiros - estudo de caso: o conselho do leitor do jornal Zero Hora

Arócha, Camila Cardozo 20 July 2009 (has links)
Made available in DSpace on 2015-03-05T18:25:54Z (GMT). No. of bitstreams: 0 Previous issue date: 20 / Nenhuma / No atual momento histórico em que vivemos, a busca pela informação, pelo conhecimento do que está acontecendo em nosso bairro, cidade, país ou mesmo em qualquer parte do mundo parece concorrer lado a lado com as nossas necessidades básicas. Manter-se informado, parece somar às pessoas certo status social, um valor na sociedade: o de “estar por dentro das notícias”. Os meios de comunicação, especificamente os jornais de circulação diária, passam, assim, a assumir a posição de mercadoria de consumo. Para melhorar a qualidade da mídia e assegurar sua responsabilidade social, surgem os conselhos de imprensa, que buscam a qualificação ao darem voz ao seu público. Nesse contexto, a presente pesquisa consistiu em um estudo junto ao Conselho do Leitor do jornal Zero Hora, principal jornal em termos de circulação do Estado do Rio Grande do Sul – Brasil, a fim de observar, descrever e analisar a dinâmica de funcionamento desse Conselho e se ele interfere ou não no processo de elaboração das edições do jornal. O estudo / In the present historical moment we are living, the search for knowledge and information about what is happening in our neighborhood, city, country or even ever part of the world, seems to be running along with our basic needs. To be informed, seems to add some social status to people, a value for being “inside the news”. The media, specially the daily newspapers, now start to assume the position of commodity. To improve the media quality and keep its social responsibility, Press Councils appeared, opening space to its audience to raise quality. From this point on, this research consists in a study in the Reader’s Council of the Zero Hora newspaper, the most important newspaper in the State of Rio Grande do Sul – Brazil, to describe and to analyze the dynamics operations of this Council, observing if it interferes or not on the elaboration process of the newspaper’s editions. Looking through this theme, the need of using many evidence sources appeared (participating/collaborative observation, semi-structure
393

A viol?ncia na m?dia : um estudo de caso sobre a cobertura da criminalidade pela imprensa no RS

Etchichury, Carlos 10 August 2010 (has links)
Made available in DSpace on 2015-04-14T14:46:07Z (GMT). No. of bitstreams: 1 437318.pdf: 1142354 bytes, checksum: 6ce7a8802560b8950c312b31fa675b60 (MD5) Previous issue date: 2010-08-10 / This dissertation analysis the deep transformation on journalistic covering about violent criminality since the middle of the 80?s, when the main newspapers on Brazil started to extend its contents, to diversify sources and to qualify stories. After Brazil?s redemocratization, that concurs with the explosion of violent criminality in the country, isolated cases that used to homogenize media?s attention get out of the press focus and are replaced by contextualized stories on public security and security politics. To analise how and why these transformations have occurred on Zero Hora?s covering and what are its implications in the journalists professional context and in the routine of the editorial office, interviews have been made with journalists that act or have acted in ZH Police section. The answers, that do not intend to be definitive, have been reached analyzing the speech of those professionals, enlightened by Bourdieu?s teorical framework. Beyond the answers, elements that suggest a new stage of the journalistic covering have been identified in the agenda of repressive politics to fight violent criminality nowadays. / Esta disserta??o analisa a profunda transforma??o ocorrida na cobertura jornal?stica da criminalidade violenta a partir de meados da d?cada de 80, quando os principais jornais do Brasil come?am a ampliar suas abordagens, a diversificar fontes e a qualificar mat?rias. Ap?s a redemocratiza??o do Brasil, que coincide com a explos?o da criminalidade no pa?s, saem de foco casos isolados, que hegemonizavam a aten??o da imprensa, e ganham espa?o as reportagens contextualizadas sobre seguran?a p?blica e pol?tica de seguran?a. Para analisar como e por que as transforma??es na cobertura ocorreram em Zero Hora e quais as implica??es, no contexto profissional dos jornalistas e na rotina da Reda??o, da mudan?a na forma como a viol?ncia passou a ser tratada, realizou-se entrevistas com jornalistas que atuam ou atuaram na editoria de Pol?cia de ZH. As respostas, que n?o se pretendem definitivas, foram encontradas atrav?s da an?lise dos discursos dos profissionais,?luz do arcabou?o te?rico proposto por Bourdieu. Al?m das respostas, identificou-se elementos que sugerem uma nova etapa da cobertura jornal?stica no agendamento de pol?ticas repressivas de combate a criminalidade violenta nos dias atuais.
394

Política e controle do crime: a Indústria da Tolerância em Manaus

Mota, Guilherme Gustavo Vasques 26 June 2012 (has links)
Made available in DSpace on 2016-04-25T20:20:46Z (GMT). No. of bitstreams: 1 Guilherme Gustavo Vasques Mota.pdf: 6195793 bytes, checksum: af680584ab1cc0d15ca794941b16d352 (MD5) Previous issue date: 2012-06-26 / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior / Viewing the role of media in disseminating the crime in Manaus, will be analyzed the role played by newspapers "Ten minutes" and "Manaus today" which sell their copies a day for those who live in areas of the city's outskirts, publishing news punishable acts that occurred in these areas. In the pages of newspapers, every day, there is the exposure of people involved in these events as "pests" and the proposed treatment of these, by establishing a system of "zero tolerance". This thesis attempts to prove that the performance of newspapers is driven by neoliberal rationality, power diagrams of the control society and the criminal policies "Law and Order" and "Zero Tolerance", which proposes a scheme covering the whole society in that punishes any deviation, which is in full operation in the main neoliberal democracies today. In peripheral areas, where crime is related to socio-economic, the effects of "zero tolerance" are more improved in way that produces a fracture in the current "tolerant society" rooted in international universalism, producing a new figuration of the crime pests in neoliberalism. The papers thus act as agents of the subjective processes of readers and bring different tactics to determine the behavior of those who inhabit the suburbs, by the spread of "zero tolerance" as the ideal way to fight crime in these areas, allowing the expansion of an "Tolerance Industry" in Manaus that enriches with the report of the punishment / Visualizando a atuação dos meios de comunicação na veiculação da criminalidade em Manaus, se analisa o papel desempenhado pelos jornais Dez minutos e Manaus hoje que têm como principal público-alvo , habitantes as áreas de periferia da cidade, publicando notícias sobre atos puníveis ocorridos nessas áreas. Nas páginas dos jornais, diariamente, se verifica a exposição das pessoas envolvidas nesses fatos como pestes e a proposta de tratamento dessas, pelo estabelecimento de um regime de tolerância zero . A presente dissertação pretende comprovar que esta atuação dos jornais é orientada pela racionalidade neoliberal, os diagramas de poder da sociedade de controle e as políticas criminais Lei e ordem e Tolerância zero , que propõe um regime que abrange toda a sociedade, em que se pune qualquer desvio, algo que está em pleno funcionamento nas principais democracias neoliberais na atualidade. Nas áreas de periferia, onde a criminalidade relaciona-se a questões socioeconômicas, os efeitos da Tolerância zero são mais sentidos produzindo uma fratura exposta na atual sociedade da tolerância enraizada no universalismo internacional, produzindo a nova figuração das pestes da criminalidade no neoliberalismo. Os jornais, assim, atuam como agenciadores dos processos de subjetivação dos leitores e trazem diferentes táticas para assujeitar habitantes das periferias, pela difusão da tolerância zero como forma ideal de combate à criminalidade nessas áreas, permitindo também a expansão de uma Indústria da Tolerância em Manaus que enriquece com o relato da punição
395

Política e controle do crime: a Indústria da Tolerância em Manaus

Mota, Guilherme Gustavo Vasques 26 June 2012 (has links)
Made available in DSpace on 2016-04-26T14:53:42Z (GMT). No. of bitstreams: 1 Guilherme Gustavo Vasques Mota.pdf: 6195793 bytes, checksum: af680584ab1cc0d15ca794941b16d352 (MD5) Previous issue date: 2012-06-26 / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior / Viewing the role of media in disseminating the crime in Manaus, will be analyzed the role played by newspapers "Ten minutes" and "Manaus today" which sell their copies a day for those who live in areas of the city's outskirts, publishing news punishable acts that occurred in these areas. In the pages of newspapers, every day, there is the exposure of people involved in these events as "pests" and the proposed treatment of these, by establishing a system of "zero tolerance". This thesis attempts to prove that the performance of newspapers is driven by neoliberal rationality, power diagrams of the control society and the criminal policies "Law and Order" and "Zero Tolerance", which proposes a scheme covering the whole society in that punishes any deviation, which is in full operation in the main neoliberal democracies today. In peripheral areas, where crime is related to socio-economic, the effects of "zero tolerance" are more improved in way that produces a fracture in the current "tolerant society" rooted in international universalism, producing a new figuration of the crime pests in neoliberalism. The papers thus act as agents of the subjective processes of readers and bring different tactics to determine the behavior of those who inhabit the suburbs, by the spread of "zero tolerance" as the ideal way to fight crime in these areas, allowing the expansion of an "Tolerance Industry" in Manaus that enriches with the report of the punishment / Visualizando a atuação dos meios de comunicação na veiculação da criminalidade em Manaus, se analisa o papel desempenhado pelos jornais Dez minutos e Manaus hoje que têm como principal público-alvo , habitantes as áreas de periferia da cidade, publicando notícias sobre atos puníveis ocorridos nessas áreas. Nas páginas dos jornais, diariamente, se verifica a exposição das pessoas envolvidas nesses fatos como pestes e a proposta de tratamento dessas, pelo estabelecimento de um regime de tolerância zero . A presente dissertação pretende comprovar que esta atuação dos jornais é orientada pela racionalidade neoliberal, os diagramas de poder da sociedade de controle e as políticas criminais Lei e ordem e Tolerância zero , que propõe um regime que abrange toda a sociedade, em que se pune qualquer desvio, algo que está em pleno funcionamento nas principais democracias neoliberais na atualidade. Nas áreas de periferia, onde a criminalidade relaciona-se a questões socioeconômicas, os efeitos da Tolerância zero são mais sentidos produzindo uma fratura exposta na atual sociedade da tolerância enraizada no universalismo internacional, produzindo a nova figuração das pestes da criminalidade no neoliberalismo. Os jornais, assim, atuam como agenciadores dos processos de subjetivação dos leitores e trazem diferentes táticas para assujeitar habitantes das periferias, pela difusão da tolerância zero como forma ideal de combate à criminalidade nessas áreas, permitindo também a expansão de uma Indústria da Tolerância em Manaus que enriquece com o relato da punição
396

Estudo do ponto invariante com a temperatura (\"Zero Temperature Coefficient\") em transistores SOI Mosfet fabricados com tecnologia ultra-submicrométrica. / Zero temperature coefficient study in SOI mosfets with submicrometer technology.

Camillo, Luciano Mendes 04 February 2011 (has links)
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.
397

Investigating How Energy Use Patterns Shape Indoor Nanoaerosol Dynamics in a Net-Zero Energy House

Jinglin Jiang (5930687) 16 January 2019 (has links)
<p>Research on net-zero energy buildings (NZEBs) has been largely centered around improving building energy performance, while little attention has been given to indoor air quality. A critically important class of indoor air pollutants are nanoaerosols – airborne particulate matter smaller than 100 nm in size. Nanoaerosols penetrate deep into the human respiratory system and are associated with deleterious toxicological and human health outcomes. An important step towards improving indoor air quality in NZEBs is understanding how occupants, their activities, and building systems affect the emissions and fate of nanoaerosols. New developments in smart energy monitoring systems and smart thermostats offer a unique opportunity to track occupant activity patterns and the operational status of residential HVAC systems. In this study, we conducted a one-month field campaign in an occupied residential NZEB, the Purdue ReNEWW House, to explore how energy use profiles and smart thermostat data can be used to characterize indoor nanoaerosol dynamics. A Scanning Mobility Particle Sizer and Optical Particle Sizer were used to measure indoor aerosol concentrations and size distributions from 10 to 10,000 nm. AC current sensors were used to monitor electricity consumption of kitchen appliances (cooktop, oven, toaster, microwave, kitchen hood), the air handling unit (AHU), and the energy recovery ventilator (ERV). Two Ecobee smart thermostats informed the fractional amount of supply airflow directed to the basement and main floor. The nanoaerosol concentrations and energy use profiles were integrated with an aerosol physics-based material balance model to quantify nanoaerosol source and loss processes. Cooking activities were found to dominate the emissions of indoor nanoaerosols, often elevating indoor nanoaerosol concentrations beyond 10<sup>4</sup> cm<sup>-3</sup>. The emission rates for different cooking appliances varied from 10<sup>11</sup> h<sup>-1</sup> to 10<sup>14</sup> h<sup>-1</sup>. Loss rates were found to be significantly different between AHU/ERV off and on conditions, with median loss rates of 1.43 h<sup>-1</sup> to 3.68 h<sup>-1</sup>, respectively. Probability density functions of the source and loss rates for different scenarios will be used in Monte Carlo simulations to predict indoor nanoaerosol concentrations in NZEBs using only energy consumption and smart thermostat data.</p>
398

Zero-shot visual recognition via latent embedding learning

Wang, Qian January 2018 (has links)
Traditional supervised visual recognition methods require a great number of annotated examples for each concerned class. The collection and annotation of visual data (e.g., images and videos) could be laborious, tedious and time-consuming when the number of classes involved is very large. In addition, there are such situations where the test instances are from novel classes for which training examples are unavailable in the training stage. These issues can be addressed by zero-shot learning (ZSL), an emerging machine learning technique enabling the recognition of novel classes. The key issue in zero-shot visual recognition is the semantic gap between visual and semantic representations. We address this issue in this thesis from three different perspectives: visual representations, semantic representations and the learning models. We first propose a novel bidirectional latent embedding framework for zero-shot visual recognition. By learning a latent space from visual representations and labelling information of the training examples, instances of different classes can be mapped into the latent space with the preserving of both visual and semantic relatedness, hence the semantic gap can be bridged. We conduct experiments on both object and human action recognition benchmarks to validate the effectiveness of the proposed ZSL framework. Then we extend the ZSL to the multi-label scenarios for multi-label zero-shot human action recognition based on weakly annotated video data. We employ a long short term memory (LSTM) neural network to explore the multiple actions underlying the video data. A joint latent space is learned by two component models (i.e. the visual model and the semantic model) to bridge the semantic gap. The two component embedding models are trained alternately to optimize the ranking based objectives. Extensive experiments are carried out on two multi-label human action datasets to evaluate the proposed framework. Finally, we propose alternative semantic representations for human actions towards narrowing the semantic gap from the perspective of semantic representation. A simple yet effective solution based on the exploration of web data has been investigated to enhance the semantic representations for human actions. The novel semantic representations are proved to benefit the zero-shot human action recognition significantly compared to the traditional attributes and word vectors. In summary, we propose novel frameworks for zero-shot visual recognition towards narrowing and bridging the semantic gap, and achieve state-of-the-art performance in different settings on multiple benchmarks.
399

A qualitative analysis of how learning from Serious Adverse Incident reviews can contribute to reducing deaths by suicide of people in the care of Mental Health Services

Ramsey, Colette January 2019 (has links)
The overall aim of the research is contribute to a reduction in suicides within mental health services. This study will explore the learning process for mental health services following patient suicides in Northern Ireland (NI). It will focus on how the recommendations contained in Serious Adverse Incident reports, which are completed following all patient suicides, are translated into practice. The study will examine all SAI reports completed from January 2015 to December 2016. Focus groups with mental health professionals throughout NI will then be used to increase understanding of the enablers and barriers to effective implementation of these recommendations within mental health services.
400

Properties, functionality and potential applications of novel modified iron nanoparticles for the treatment of 2,4,6-trichlorophenol

Underwood, Laura Ann January 2018 (has links)
2,4,6-trichlorophenol (TCP) is a pervasive carcinogenic water contaminant found in a wide variety of water and waste systems and is a pertinent model compound of broader aromatic organics, specifically organo-halide pesticides. These compounds are persistent in the environment and show resilience to regular water and waste treatment protocols thus warranting the development and implementation of novel treatment materials for improved contaminant removal. Zero-valent iron (ZVI) has demonstrated the ability to remove or degrade a wide variety of inorganic and organic water contaminants, including chlorophenols, and has been widely applied for in-situ groundwater remediation where contamination is often localised in a low-oxygen environment. ZVI's broader applications in water treatment have remained mainly limited due to corrosion, particle dispersion, and confinement issues in deployment. This work, therefore, explored the development, functionality, and potential application of new modified nZVI materials (nZVI-Osorb) and assessed their potential to improve iron's intrinsic functionality while also gauging the material's viability for TCP remediation in water and waste systems. Materials produced in this thesis were prepared utilising three different embedment procedures (1-pot, multiple additions, oxygen-free). All embedment methods resulted in tightly bound composites featuring high surface areas (340.2-449.1 sq. m/g) with net iron composition ranging from 10% to 29.78% by mass. Electron imaging microscopy verified even dispersion of iron throughout the substrate. Composite materials did not exhibit a delayed rate of atmospheric corrosion over nZVI controls evincing an 18% nZVI0 loss per day until reaching a stabilised concentration (7%) after 48 hrs. nZVI-Osorb composites did produce more favourable iron oxide species which remain conducive to electron transfer from core Fe0 atom. After 50 days, a majority of nZVI in nZVI-Osorb had oxidised to maghemite (30%) and magnetite (26%) compared to control nZVI producing 19% and 12% respectively. Unreactive hematite accounted for 47% of the control and just 36% of the composite. While 1-pot embedment allowed the most substantial control over final iron composition, the oxygen-free method allowed the most reliable preservation of initial nZVI0 concentrations through restricted oxidation. Materials generated through oxygen-free embedment were utilised in the following water treatment trials with TCP. Parameters related to sorption and degradation mechanisms of TCP by nZVI-Osorb were tested in aerobic conditions, e.g. surface and potable water. nZVI-Osorb materials demonstrated high extraction capacity for TCP from aqueous solutions (Qe=1286.4 ± 13.5 mg TCP/g Osorb, Qe=1253 ± 106.7 mg TCP/g nZVI-Osorb, pH 5.1, 120mg/L TCP) and followed pseudo second order kinetics. In the broader class of chlorophenols, sorptive affinity mirrored partitioning values with highly substituted chlorophenols displaying the highest sorption capacities. Degradation of TCP by nZVI-Osorb or nZVI controls was not observed due to corrosive hindrance and inadequate reductive capacity, suggesting that materials may not be suitable for highly aerated surface and potable water treatment systems. Environmental conditions pertinent to sorption and degradation mechanisms were evaluated to improve understanding and robustness of functionality in low-oxygen applications, such as wastewater and anaerobic digesters, where nZVI-Osorb treatment is anticipated to be advantageous to TCP sorption and methane production. pH was found to influence sorption dramatically. Acidic solutions below 5 found sorption > 90%. This capacity was reduced to < 30% when pH was raised above TCP pKa value (6.23) to 7 and above. Further trials found a positive effect on TCP sorption (+7.55%) linked to net pH reduction (5.1 to 3.3) with the addition of secondary acids (volatile fatty acids: acetic, propionic, butyric, 3x 100mg/L) commonly found in anaerobic digester systems. Salinity did not affect TCP sorption. The removal of dissolved and atmospheric oxygen increased total sorption (40ppm-+1.94%, 100ppm- +7.93%, 200ppm- +0.89%, 400mg/L- +14.59%) through reduced iron corrosion and the production of favorable iron oxides, but did not facilitate contaminant degradation. Biodegradation mechanisms for TCP have broadly been established, and new research has supported the improved cometabolic degradation of recalcitrant contaminants like TCP and PCP in nZVI-dosed anaerobic digesters. Model anaerobic digester systems (3.9 g/L nZVI-Osorb, 25mg/L TCP, 240 mg/L acetic, 120mg/L propionic, 120mg/L butyric acid) containing bioreactor sludge (62.5%) were observed through standard water quality diagnostics (pH, ORP, COD, head pressure) for 14 days and suggested that nZVI-Osorb did not inhibit cellular processes. Increased electron activity from iron corrosion and hydrogen gas production, increased overall pH and decreased total ORP in these AD systems. TCP degradation by-products (DCP, CP) were detected in dilute concentrations (< 0.01 mg/L) with poor recovery by LC-MS/MS. Results suggest that nZVIOsorb may be well-suited additive for AD systems. This study contributes to knowledge of the properties, functionality, and treatment mechanisms of metal-sorbent composites with a model chlorinated aromatic water contaminant in aerobic and anaerobic environments. The work identifies favourable environmental and process conditions to apply these materials in larger scale applications, particularly, anaerobic digestion and provides support for the continued refinement and improvement of nZVI based remediation systems.

Page generated in 0.0532 seconds