• Refine Query
  • Source
  • Publication year
  • to
  • Language
  • 76
  • 57
  • 16
  • 4
  • 3
  • 1
  • 1
  • 1
  • 1
  • 1
  • 1
  • Tagged with
  • 176
  • 74
  • 20
  • 19
  • 18
  • 18
  • 17
  • 13
  • 13
  • 11
  • 11
  • 10
  • 9
  • 9
  • 8
  • 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.
31

Foto e biodegradação de PEBD, PHB e suas blendas /

Lopes, Viviane Cristina Padilha. January 2011 (has links)
Orientador: José Carlos Marconato / Banca: Regina Teresa Rosim Monteiro / Banca: Adriana de Campos Pastre / Resumo: Recentemente o mundo começou a se preocupar com o consumo exacerbado de embalagens e a sua rápida descartabilidade. Por conseguinte, alternativas de amenização deste problema têm sido propostas tais como a utilização de plásticos biodegradáveis, o uso de blendas poliméricas e o emprego de aditivos que facilitem a biodegradação. Sendo assim, este trabalho teve por objetivo avaliar os diferentes tratamentos: foto, bio e foto/biotratamento, aplicados na degradação de filmes finos de PEBD, PHB e de suas blendas, empregando o fungo P. chrysosporium CCB 478 no processo biodegradativo. As blendas de PEBD/PHB foram preparadas nas composições de 90:10, 80:20 e 70:30 (m/m) juntamente com os filmes de homopolímeros pelo processo de prensagem sob aquecimento. As amostras foram submetidas à radiação UV e em seguida foram aplicados os testes de biodegradação em meio mineral líquido com o fungo P. chrysosporium CCB 478 pelo período de 120 dias. Análises de perda de massa, ângulo de contato, FTIR, análises visuais, microscopia óptica, MEV, foram técnicas utilizadas para avaliar a biodegradação. O fototratamento realizado com todas as amostras dos filmes foi relevante para o processo de adesão e colonização da superfície dos filmes. As blendas de composição 70/30 e 80/20 apresentaram alterações morfológicas e estruturais mais significativas, por MEV e FTIR, além de apresentaram melhores resultados de biodegradação, após a fotoirradiação. / Abstract: Recently the world began to worry about the high consumption and rapid disposability of packaging. Therefore, alternatives to improve this problem have been proposed such as use of biodegradable plastics, polymer blends and additivies which facilitates the biodegradation. Thus, this study aimed to evaluate the results of different treatments: biotreatment, phototreatment, and photo/biotreatment, applied on the degradation of thin films of LDPE, PHB and its blends, using as fungus Phanerochaete chrysosporium CCB 478 in biodegradation process. Blends of LDPE/PHB were prepared in the compositions of 90:10, 80:20 and 70:30 (m/m) along with homopolymers films by pressing process under heating. Samples were exposed to UV radiation and then were submitted to the biodegradation tests in liquid mineral medium with the P. chrysosporium CCB 478 fungus for 120 days. Analysis of weight loss, contact angle, FTIR, visual analysis, optical microscopy and SEM, were employed to estimate biodegradation. Phototreatment applied to all films was relevant to the adhesion process and colonization the surface films. The blends of composition 70/30 and 80/20 showed significant morphological and structural changes, verified by SEM and FTIR techniques, besides showed better results of biodegradation after photoirradiation. / Mestre
32

Factors affecting the photodegradation rates of polymers that contain (cyclopentadienyl-(carbon monoxide)-molybdenum) in the backbone

Daglen, Bevin Colleen, 1977- 09 1900 (has links)
xxii, 143 p. ; ill. (some col.) A print copy of this title is available through the UO Libraries. Search the library catalog for the location and call number. / There are compelling economic and environmental reasons for using degradable plastics in selected applications and considerable research is now devoted to devising new photodegradable polymers with improved performance. Controlling the degradation of these materials in a prescribed fashion is still a difficult problem because the parameters that influence degradation rates are not completely understood. In order to predict polymer lifetimes, to manipulate when a polymer starts to degrade, and to control the rate of degradation, it is necessary to identify the experimental parameters that affect polymer degradation rates and to understand how these parameters affect degradation. This dissertation describes the results of experiments designed to gain fundamental insight into the factors that affect the rate of polymer photodegradation. The key experimental strategy employed was the incorporation of organometallic dimers into the backbone of the polymer chains, specifically, [CpRMo(CO) 3 ] 2 (CpR = a substituted cyclopentadienyl (· 5 -C 5 H 4 R)). Incorporating these organometallic units into a polymer chain make the polymer photodegradable because the metal-metal bond can be cleaved with visible light. The photogenerated metal radicals can then be trapped by O 2 or chlorine, resulting in degradation of the polymer. Another benefit from incorporating this chromophore into the polymer backbone is that it provides the experimentalist with a convenient spectroscopic handle to monitor degradation rates. Using these model polymers, several experimental factors that can affect polymer photodegradation rates have been explored. For example, experiments showed that radical trap concentration affects degradation rates below, but not above, the polymer glass transition temperature. In addition, degradation rates as a function of irradiation temperature, tensile stress, and time-dependent morphology changes were explored for various polymers. The results of these studies suggest that the ability of the photogenerated radicals to escape the radical cage is the dominant factor in determining photodegradation efficiencies. This dissertation includes previously published and unpublished co-authored material. / Adviser: David R. Tyler
33

The Synthesis of Linear and Nonlinear Photosensitive Organometallic Polymers Containing Mo-Mo Bonds: Evaluating the Effectiveness of Click Chemistry

Brady, Sarah 03 October 2013 (has links)
This dissertation details the use of click chemistry to prepare linear and nonlinear polymers containing metal-metal bonds. The incorporation of metal-metal bonds into the polymer simplfies the degradation mechanism, allowing fundamental mechanistic studies of polymer degradation. Click chemistry offered a brand new route to explore the preparation of these useful but intricate metal-metal bond-containing polymers. Chapter I discusses the utility of these types of polymers for mechanistic studies, the preparation of metal dimers with reactive functionalities, and the previous polymerization methods which have been explored. The need for a new polymerization strategy, such as click chemistry, is described. Chapter II explains the preparation of a new metal dimer click synthon, [(η5-C5H4(CH2)3OC(O)(CH2)2C≡CH)Mo(CO)3]2, and the necessary conditions needed to polymerize the synthon using click chemistry. A high molecular weight linear polymer was prepared, suggesting click chemistry is a viable route to nonlinear polymers. Chapter III presents a second novel metal dimer click synthon, [(η5-C5H4(CH2)3N3Mo(CO)3]2, and attempts to use click chemistry to prepare a star polymer containing metal-metal bonds. A small amount of nonlinear polymer was prepared but several reactivity problems were also discovered and addressed. Due to these problems with click chemistry, Chapter IV details a brand new method for preparing asymmetric metal dimers. CpMo(CO)3-Mo(CO)3Cp(CH2)3CH=CH2 is the first reported example of an asymmetric dimer, and (CH3)3CSi(CH3)2O(CH2)3CpMo(CO)3-Mo(CO)3Cp(CH2)3OC(CH3)2OCH3 is the first example of a bifunctional asymmetric dimer. Chapter V describes the synthesis of a different type of metal dimer, (CH3)2Si[(C5H5)Mo(CO)3]2, which is polymerized by thermal ring opening polymerization. The dimer did not polymerize as expected and yielded an interesting polymer which has both Mo-Mo single bonds and Mo≡Mo triple bonds. Finally, Chapter VI provides a summary of the work as well as an honest perspective of using click chemistry to prepare metal-metal bond-containing polymers. This dissertation includes previously published and unpublished co-authored material. / 10000-01-01
34

Foto e biodegradação de PEBD, PHB e suas blendas

Lopes, Viviane Cristina Padilha [UNESP] 18 April 2011 (has links) (PDF)
Made available in DSpace on 2014-06-11T19:27:24Z (GMT). No. of bitstreams: 0 Previous issue date: 2011-04-18Bitstream added on 2014-06-13T18:56:08Z : No. of bitstreams: 1 lopes_vcp_me_rcla.pdf: 959048 bytes, checksum: 8ef5fde75931039770927a47c11ea7f8 (MD5) / Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq) / Recentemente o mundo começou a se preocupar com o consumo exacerbado de embalagens e a sua rápida descartabilidade. Por conseguinte, alternativas de amenização deste problema têm sido propostas tais como a utilização de plásticos biodegradáveis, o uso de blendas poliméricas e o emprego de aditivos que facilitem a biodegradação. Sendo assim, este trabalho teve por objetivo avaliar os diferentes tratamentos: foto, bio e foto/biotratamento, aplicados na degradação de filmes finos de PEBD, PHB e de suas blendas, empregando o fungo P. chrysosporium CCB 478 no processo biodegradativo. As blendas de PEBD/PHB foram preparadas nas composições de 90:10, 80:20 e 70:30 (m/m) juntamente com os filmes de homopolímeros pelo processo de prensagem sob aquecimento. As amostras foram submetidas à radiação UV e em seguida foram aplicados os testes de biodegradação em meio mineral líquido com o fungo P. chrysosporium CCB 478 pelo período de 120 dias. Análises de perda de massa, ângulo de contato, FTIR, análises visuais, microscopia óptica, MEV, foram técnicas utilizadas para avaliar a biodegradação. O fototratamento realizado com todas as amostras dos filmes foi relevante para o processo de adesão e colonização da superfície dos filmes. As blendas de composição 70/30 e 80/20 apresentaram alterações morfológicas e estruturais mais significativas, por MEV e FTIR, além de apresentaram melhores resultados de biodegradação, após a fotoirradiação. / Recently the world began to worry about the high consumption and rapid disposability of packaging. Therefore, alternatives to improve this problem have been proposed such as use of biodegradable plastics, polymer blends and additivies which facilitates the biodegradation. Thus, this study aimed to evaluate the results of different treatments: biotreatment, phototreatment, and photo/biotreatment, applied on the degradation of thin films of LDPE, PHB and its blends, using as fungus Phanerochaete chrysosporium CCB 478 in biodegradation process. Blends of LDPE/PHB were prepared in the compositions of 90:10, 80:20 and 70:30 (m/m) along with homopolymers films by pressing process under heating. Samples were exposed to UV radiation and then were submitted to the biodegradation tests in liquid mineral medium with the P. chrysosporium CCB 478 fungus for 120 days. Analysis of weight loss, contact angle, FTIR, visual analysis, optical microscopy and SEM, were employed to estimate biodegradation. Phototreatment applied to all films was relevant to the adhesion process and colonization the surface films. The blends of composition 70/30 and 80/20 showed significant morphological and structural changes, verified by SEM and FTIR techniques, besides showed better results of biodegradation after photoirradiation.
35

Processos ópticos e interação entre nanopartículas e sistemas moleculares / Optical processes and interactions between nanoparticles and molecular systems

Fernando Massayuki Tsutae 23 February 2011 (has links)
A transferência de carga entre adsorbatos moleculares doadores e nanopartículas (NPs) semicondutoras aceitadoras têm encontrado extensivas aplicações recentes em células fotovoltaicas e de combustíveis, em fotocatálise e em eletrônica molecular. Além disso, NPs têm sido usadas como suporte para reagentes moleculares, fotosintetizadores e fármacos para variados fins. A eficiência destes dispositivos moleculares depende do estudo detalhado da dinâmica de transferência de carga na interface entre uma NP e moléculas adsorvidas e, em particular, da transferência lateral de energia entre moléculas adsorvidas. Além disso, é necessário otimizar de um lado a atração Coulombiana entre doadores oxidados e aceitadores reduzidos e por outro lado as reações de ancoramento de modo que elas não fiquem limitadas ao encontro estocástico e difuso em solução. Em especial, tem-se observado uma crescente demanda por dispositivos fotovoltaicos híbridos construídos a partir de NPs de dióxido de titânio (TiO2). Estudos de estabilidade à longo prazo e modificações na interface de tais dispositivos são essenciais para se obter uma melhor eficiência. Também já é bem conhecida na literatura o uso de NPs de TiO2 como uma alternativa na degradação de corantes e tratamento de efluentes. Outra classe de estudos igualmente importante consiste na aplicação de porfirinas e seus derivados na geração de oxigênio singleto e no tratamento de câncer. Portanto, é de grande interesse o estudo de sistemas baseados nas propriedades das porfirinas e TiO2. O presente trabalho de mestrado teve como objetivo o estudo por técnicas espectroscópicas a) da adsorção de moléculas de porfirina emissora de luz na superfície de NPs semicondutoras de TiO2, b) dos processos ópticos envolvidos na transferência de carga e de energia na interface entre NP aceitadora e as porfirinas doadoras adsorvidas e do efeito da NP na fotoestabilidade e fotodegradação da porfirina. Em nosso estudo, escolhemos uma porfirina (Photogem® ou PG) como padrão de sistema molecular, pois apresenta bandas de absorção e emissão bem definidos. Foram utilizadas séries distintas de NPs de TiO2 com diferentes razões de área superficial por volume e porcentagens das fases predominantes rutilo e anatase preparadas sob diversas condições pelo método dos precursores poliméricos. Desenvolvemos um método que consiste na centrifugação das NPs juntamente com as moléculas adsorvidas e posterior analise óptica da solução sobrenadante para estudar a adsorção das porfirinas na superfície do TiO2. Observamos que NPs de TiO2 com predominância da fase anatase em sua estrutura possui maior interação e, consequentemente, maior adsorção molecular. A fase rutilo possui baixa adsorção molecular por ser extremamente estável. A afinidade e interação entre porfirina e partículas de TiO2 em solução foram analisadas para diferentes valores de pH. Também foram estudados efeitos da agregação e cobertura molecular nos processos de fotodegradação e de transferência lateral de energia entre moléculas adsorvidas. / Actually, charge transfer processes between molecular adsorbate donors and semiconductor nanoparticles (NPs) acceptors have found extensive applications in photocatalysis, photovoltaics cells and molecular electronics. Moreover, NPs have been used as carrier by molecular reagents, photosynthesizing and drugs for various purposes. The efficiency of these molecular devices depends on the detailed study of the dynamics of charge transfer at the interface between NPs and adsorbed molecules and, in particular, the lateral energy transfer between adsorbed molecules. Furthermore, it is necessary to optimize the Coulomb attraction between oxidized donors and reduced acceptors as well as anchoring reactions so that they are not limited by stochastic and diffuse interaction in solution. In particular, there has been a growing demand for hybrid photovoltaic devices based on nanoparticles of titanium dioxide (TiO2-NPs). Studies of long-term stability and interface modification are essential to obtain devices with better efficiency. Also well known in literature it is the employ of TiO2-NPs as an alternative in dye degradation and wastewater treatment. Another class of important study is based on the application of porphyrins and their derivatives in the generation of singlet oxygen and treatment of cancer. Thus, it is of great interest the study of systems based on porphyrin and TiO2 properties. The present work had as objective the study by spectroscopic technics: a) the adsorption of a light-emitting porphyrin on the TiO2-NPs surfaces, b) optical processes involved in charge and energy transfer in the interface between NP acceptor and porphyrins donors and the effect of NP on the photostability and photodegradation of porphyrins. In our study, we chose a porphyrin (or PG Photogem ®) as standard molecular system, because it shows well defined absorption and emission bands. We used TiO2-NPs which differ in area/volume ratios and in the percentage of rutile and anatase phases that predominates under different conditions of preparation by polymeric precursor method. We developed a method based on the centrifugation of the NPs with adsorbed molecules and subsequent optical analysis of the supernatant solution to study the adsorption of porphyrins on TiO2-NPs surfaces. We observed that TiO2-NPs with predominantly anatase phase in its structure has greater interaction and, consequently, higher molecular adsorption. The rutile phase has low molecular adsorption due to your great stability. The affinity and interaction between porphyrin and TiO2-NPs in solution were analyzed for different pH values. Other subjects discussed in this work include molecular aggregation effects and coverage during photodegradation and lateral energy transfer between adsorbed molecules.
36

Obtenção da blenda polipropileno reprocessado/poliestireno de alto impacto e seu comportamento diante a radiação UV. / Obtenained blend polipropylene reprocessed/polyestyrene hight impact of behavoir exposed UV radiation.

Laércio Lima Fernandes 26 June 2009 (has links)
A utilização da tecnologia de produção de blendas poliméricas sempre está relacionada com a soma das características individuais de cada um dos componentes da blenda. No caso específico da blenda polipropileno - PP e poliestireno de alto impacto - HIPS esta relação está mais especificamente relacionada com a melhoria na propriedade de resistência ao impacto do PP. Contudo, outras propriedades também devem ser avaliadas. Um outro fator bastante importante é como esta blenda se comportará diante situações reais de uso, por exemplo, exposição à radiação UV. Este trabalho apresenta as propriedades mecânicas e morfológicas da blenda PP/HIPS na composição 90/10, 80/20 e 70/30, sendo que na obtenção dessa blenda utilizou-se dois tipos de polipropileno, um previamente termodegradado (PPreprocessado) e outro virgem (PPv). Foram testados na blenda três tipos de compatibilizantes (SBS, SEBS e PP-g-PS) com o intuito de melhorar a adesão entre as fases. Além disso esse trabalho apresenta os efeitos da radiação UV nas blendas e nos componentes que a formam. Os materiais foram expostos a radiação artificial e foram caracterizados quanto as suas modificações químicas, físicas e mecânicas. As superfícies de fratura dos corpos de prova de impacto foram também analisadas. Por meio dos resultados obtidos pode-se perceber que a mistura PP/HIPS apresenta imiscibilidade entre seus componentes e que a diferença entre os dois tipos de PP resulta em diferentes valores para as propriedades das misturas. Entre os compatibilizantes adicionados o SBS foi o que proporcionou melhores resultados. Ao se analisar a influência da radiação UV nos componentes que formam as blendas PP/HIPS observou se que o PPrep e o PPvir se mostraram sensíveis ao processo degradativo. As propriedades dos materiais diminuíram drasticamente sob efeito da radiação UV. Entretanto quando foram estudados os efeitos da radiação UV nas propriedades das blendas PP/HIPS e o PPrep/HIPS foi observado que as blendas com maiores proporções de HIPS foram mais fotoestáveis, ou seja, as blendas tiveram menores perdas nas propriedades com o tempo de exposição. / Polymer blend technology is always related with a synergism between the individual properties of the components of the blend components. In the specific case of the polypropylene (PP) and high impact polystyrene (HIPS) blend, this relation is based on the impact strength improvement of PP. However, other properties should also be evaluated. Another important factor is the blend behavior upon real use conditions, such as UV radiation exposure. The mechanical and morphological properties of PP/HIPS blends are presented in this work. Two types of polypropylene were used during the blend preparation: one previously thermodegraded (reprocessed PP) and another virgin (PPv). In addition, UV radiation effects on the blends and on their components are shown. The materials were exposed to artificial radiation, and this exposure was characterized by means of chemical, physical and mechanical modification, as well as by fracture surface analysis. The results showed that the PP/HIPS blend presents immiscibility between its components. The difference between the two polypropylenes used resulted in differences in the blends properties. Besides that, the blends with higher HIPS content showed greater photostability when exposed to UV radiation.
37

Degradação de poliestirenossulfonato de sódio fotossensibilizada pelo corante QTX / Degradation of poly(styrenesulfonate) photosensitised by QTX dye

Josy Anteveli Osajima 13 October 2009 (has links)
O mecanismo de degradação da solução de poliestirenossulfonato de sódio (PSS) fotossensibilizada por cloreto de 2-hidroxi-3-(3,4-dimetil-9-oxo-9H-tioxanton-2-iloxi)-N,N,N-trimetil-1-propano (QTX) foi investigado. Inicialmente, foi estudada a fotodegradação de QTX em solução aquosa. Os fotoprodutos gerados pela fotólise foram caracterizados em sulfonas e sulfóxidos, que foram identificados por CLAE-EM. A fotodegradação de QTX em solução aquosa foi também acompanhada pelos espectros de absorção UV-Vis, sugerindo a formação de sulfóxidos. As reações elementares de QTX em solução aquosa foram investigadas através da fotólise por pulso de laser. O valor das constantes de supressão do estado triplete de QTX na presença de sorbato de potássio e hidroquinona foram próximas ao valor de constante difusional. A combinação dos resultados obtidos pelas diferentes técnicas possibilitou a proposição do mecanismo para degradação da QTX. A fotodegradação de PSS em solução aquosa na presença e na ausência de QTX foi monitorada por cromatografia de exclusão de tamanho e viscosidade. A fotodegradação de PSS foi observada somente na presença de QTX. Nesta condição uma diminuição de <span style=\"text-decoration: overline\">Mw foi observada, que significa quebra de cadeia aleatória. A degradação PSS/QTX também foi investigada na presença do sorbato de potássio, um supressor de triplete. Neste caso, ocorreu um aumento na porcentagem de degradação. Estes resultados sugeriram que o mecanismo de degradação de PSS fotossensibilizada por QTX ocorre principalmente pela QTX excitada no singlete abstrair um hidrogênio do polímero e na presença de oxigênio leva a formação de radicais, que contribuem para o processo de degradação. / The poly(styrenesulfonate) (PSS) photosensitised by 2-hydroxy-3-(3,4-dimethyl-9-oxo-9H-thioxanthen-2-yloxy)-N,N,N-trimethyl-1-propanium chloride (QTX) solution degradation mechanism was investigated. Initially, the photodegradation of QTX in aqueous solution was studied. The photoproducts generated photolysis were characterized as being sulfones and sulfoxides, which were identified by HPLC-MS. The photodegradation of QTX in aqueous solution was also followed by UV-Vis absorption spectra, suggesting the formation of sulfoxides. The elementary reactions of QTX in aqueous solution were investigated by laser flash photolysis. The quenching rate constant values of the triplet state QTX in the presence of potassium sorbate and hydroquinone were close to the value of diffusion constant. It was possible to propose the mechanism of QTX degradation combining the results from the different techniques. The photodegradation PSS in aqueous solution in the presence and absence of QTX was monitored by size exclusion chromatography and viscosity. The photodegradation of PSS was observed only in the presence of QTX. In this condition a decrease of <span style=\"text-decoration: overline\">Mw was observed, which means the random chain scission. The PSS/QTX degradation was also investigated in the presence of potassium sorbate, a triplet quencher. In this case, an increase of degradation percentage occurred. These results suggested that the degradation mechanism of PSS degradation photosensitised by QTX occurs mainly by the singlet excited QTX abstracts a hydrogen from the polymer and in the presence of oxygen leads to radicals formation which contributed to the degradation process.
38

Photodegradation of organic dyes with nanotitania embedded in hydrogels

Alshehri, Maysa 01 July 2016 (has links)
The objective of this research was to study the adsorption and photodegradation of Malachite Green (MG) dye by using poly(2-hydroxyethylmethacrylate) (PHEMA) hydrogel and nanocomposite TiO2PHEMA hydrogel. The nanocomposite gels were characterized by FT-IR and XRD. The adsorption of MG dye was examined through monitoring UV-Vis absorption. The kinetic study indicated that the adsorption follows the first order kinetics. The adsorption equilibrium data fit well to the Langmuir isotherm model. The photodegradation of MG dye was examined using TLC UV lamp and medium pressure Hg lamp. It was determined that the unloaded composite gels adsorb MG dye from the solution at the beginning while under the photochemical condition. The dye in the gel was eventually photodegraded, indicating that the photodegradation process is still effective to dyes in the gel system. The composite gels containing anatase/rutile mixed phase titania are much better photocatalysts than those containing pure phase titania (either rutile or anatse).
39

Contribution à l’étude de la présence et du devenir des résidus de médicaments dans les compartiments aquatiques

Bui, Van Hoi 27 November 2013 (has links)
La présence de résidus de médicaments a été évaluée dans des eaux superficielles et des effluents de huit stations d'épuration (quatre rejetant dans l'estuaire de Seine dans le cadre du projet Medseine financé par le GIP Seine- Aval, quatre dans le cadre du projet Toxstep financé par l'Anses (ex-Afsset). Une centaine de molécules a été systématiquement recherchée dans les deux types d'eaux en appliquant des méthodologies analytiques impliquant une extraction solide liquide suivie une analyse par LC-MS/MS. Un suivi saisonnier des rejets de médicaments a été effectué également. Des résidus de médicaments ont été systématiquement quantifiés dans les deux types d'eaux. Les concentrations mesurées dans des eaux de surface sont significatives pour certains composés : de 1 à 108 ng/L pour diclofénac, de 2 à 324 ng/L pour ibuprofène. Pour d’autres, les valeurs sont beaucoup plus faibles : de 2 à 13 ng/L pour sulfapyridine, de 1 à 5 ng/Lpour nordiazépam. Dans les effluents de STEP, les anti-inflammatoires, les β-bloquants, les macrolides et les fluoroquinolones sont plus souvent détectés. Leurs concentrations peuvent varier fortement : de 62 ng/L à 10 μg/L pour sotalol, de 39 ng/L à 8 μg/L pour aténolol et plus particulièrement de 32ng/L jusqu’à 127 μg/L pour paracétamol. Par ailleurs, la stabilité des résidus de médicaments vis à vis des rayonnements lumineux a été évaluée. Des irradiations UV (à 254 nm) pouvant potentiellement être utilisés en étape finaleavant rejet dans des zones particulièrement sensibles ont été appliquées (avec des doses allantjusqu'à 1500 J/m2. Par ailleurs, compte tenu du fait que les effluents sont ensuite majoritairement rejetés dans des eaux superficielles, ils sont soumis aux rayonnements solaires et cette exposition a également été évaluée. Le phénomène de photodégradation à 254 nm a été bien observé sur certains composés comme diclofénac, kétoprofène (> 90% dégradé), ciprofloxacine,norfloxacine (jusqu’à 75% dégradé). L’azithromycine, la clarithromycine, la carbamazépine et l’aténolol... sont des composés plus stables avec les rayonnements lumineux. En exposant sous lumière solaire simulée, le diclofénac, la kétoprofène, la ciprofloxacine et la norfloxacine sontaussi des composés sensibles (> 90% dégradé) après 24 h d’exposition (172,8 kJ/m2). La carbamazépine, la sulfaméthoxazole, l’aténolol, bisoprolol et métoprolol sont des composés plus stables observés. / The presence of pharmaceuticals was evaluated in Seine surface waters and in eight wastewater treatment plants (WWTP) effluents (4 WWTP within MEDSEINE - GIP Seine – Aval project and 4 WWTP within TOXSTEP – ANSES project. A hundred molecules was systematically reseached in both types of waters by applying the analytical methodologies (SPE solid phase extraction followed by LC-MS/MS analysis). A seasonal monitoring of pharmaceutical residues was also carried out. The pharmaceutically residues have been systematically quantified in this both types of water. The concentrations in suface of waters are significative for some molecules: 1 – 108 ng/L for diclofenac, 2 – 324 ng/L for ibuprofen and the values are weakly for some molecules: 2 – 13 for sulfapyridine, 1 – 5 for nordiazepam. Non steroidal anti-inflammatory drugs, β-blockers, macrolides and fluoroquinolones are mostly founded in the effluents of WWTP. Their concentrations were measured in the range: 62 ng/L – 10 µg/L for sotalol, 39 ng/L – 8 µg/L for atenolol, 32 ng/L – up to 127 µg/L for paracetamol.Moreover, the stability of pharmaceuticals was evaluated with light radiation . UV irradiation (at 254 nm) potentially used in the final WWTP before discharge in particularly areas have been applied (with a dose up to 1500 J/m2). Sunlight simulations have also been done. The phenomenon of photodegradation at 254 nm has been observed for some molecules such as : diclofenac, ketoprofen (>90% degraded), ciprofloxacine, norfloxacine (up to 75% degraded). Azithromycinem clarithromycine, carbamazepine and atenolol are most stable molecules observed. Exposing under simulated sunlight, diclofenac, ketoprofen, ciprofloxacine and norfloxacine are also sensitive molecules (>90 % degraded) after 24 hours of exposure (172.8 kJ/m2). Carbamazepine, sulfamethoxazole, atenolol, metoprolol and bisoprolol are most stable molecules observed.
40

Determining Kinetics for Simulated Sunlight-Exposed Oil Compounds

Kountz, Dustin D 13 August 2014 (has links)
Understanding of the fate of oil in the environment is of utmost importance; however, accurate, predictive models are still in very early stages. To aid in the development of these models, photodegradation of selected polycyclic aromatic hydrocarbons (PAHs) in an n-alkane hydrocarbon matrix was followed for individual PAHs and mixtures of PAHs similar to that found in the Deepwater Horizon spill. Tetracene in tetradecane photodegraded quickest of all observed PAHs, with a loss of 99% after only one hour of irradiation. Binary mixtures of PAHs showed different degradation amounts, including changes in PAH kinetics. These results suggest that the formation of dimers or aggregates as well as photosensitization reaction is important in the degradation of PAHs in oil. Kinetics of PAH photodegradation and PAH sensitized photodegradation will be presented. This information will provide a better understanding of the fate of oil in environmental systems.

Page generated in 0.114 seconds