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  • 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.
241

Effets de l'activité bactérienne réductrice du fer ferrique et des nitrates sur les transformations des produits de corrosion magnetite et sidérite de l'acier non allié / Effects of iron-reducing bacteria and nitrate-reducing bacteria on the transformations of iron corrosion products, magnetite and siderite, formed at the surface of non-alloy steel

Etique, Marjorie 28 November 2014 (has links)
En France, il est envisagé de stocker en formation géologique profonde les déchets radioactifs vitrifiés à haute activité et vie longue dans un conteneur en acier inoxydable chemisé par un surconteneur en acier non allié. Les principaux produits de corrosion attendus à la surface de ce dernier, i.e. la sidérite (FeIICO3) et la magnétite (FeIIFeIII2O4), jouent un rôle protecteur contre la corrosion en tant que couche passivante. Ce travail de thèse visait à étudier l’influence des groupes métaboliques bactériens réducteurs du fer ferrique (IRB) et des nitrates (NRB) sur les transformations de ces produits de corrosion en anoxie. Des souches modèles de NRB (Klebsiella mobilis) et IRB (Shewanella putrefaciens) ont, dans un premier temps, été incubées en présence de suspension de sidérite ou de magnétite, afin d’exacerber les processus de transformation du fer du fait d’une surface spécifique élevée, puis dans un second temps, en présence de films électrogénérés de ces produits pour se rapprocher des conditions d’un acier non allié corrodé en anoxie. Ces souches bactériennes sont capables de transformer la sidérite et la magnétite par des processus microbiens directs ou indirects et de conduire à la formation de rouille verte carbonatée (FeII4FeIII2(OH)12CO3). Ce composé occupe une place centrale dans le cycle biogéochimique du fer en anoxie en tant que transitoire commun à plusieurs réactions microbiennes mobilisant le fer sous deux états d’oxydation différents FeII et FeIII. L’originalité de ce travail de thèse est donc de montrer que des métabolismes bactériens inaccoutumés tels que les NRB ou les IRB sont susceptibles de jouer un rôle dans les processus de biocorrosion / Radioactive waste is one of the major problems facing the nuclear industry. To circumvent this issue France plans to store vitrified high-level nuclear waste in a stainless steel container, placed into a non-alloy steel overpack, at a depth of 500m in an argillaceous formation. The main iron corrosion products formed at the surface of the non-alloy steel are siderite (FeIICO3) and magnetite (FeIIFeIII2O4). These compounds are formed in the anoxic conditions present in the nuclear waste repository and play a protective role against corrosion as a passive layer. This work aims to investigate the activity of nitrate-reducing bacteria (NRB, Klebsiella mobilis) and iron-reducing bacteria (IRB, Shewanella putrefaciens) during the transformation of siderite and magnetite, especially those involved in anoxic iron biogeochemical cycle. Klebsiella mobilis and Shewanella putrefaciens were first incubated with siderite or magnetite suspensions (high surface specific area) in order to exacerbate the microbial iron transformation, subsequently incubated with a magnetite/siderite film synthesized by anodic polarization at applied current density. The transformation of siderite and magnetite by direct or indirect microbial processes led to the formation of carbonated green rust (FeII4FeIII2(OH)12CO3). As a transient phase shared by several bacterial reactions involving FeII and FeIII, this compound is the cornerstone of the anoxic iron biogeochemical cycle. The novelty of this thesis is the consideration of bacterial metabolisms of NRB and IRB often overlooked in biocorrosion processes
242

Magnetická modifikace mikrobiálních buněk / Magnetic modification of microbial cells

BALDÍKOVÁ, Eva January 2013 (has links)
Baker´s yeast (Saccharomyces cerevisiae) were magnetically modified by three different methods, namely, surface modification by magnetic fluid, entrapment of cells into alginate and covalent immobilization on particles of magnetic chitosan. The ability of H2O2 decomposition was tested for all types of modification. It is apparent that the most amount of hydrogen peroxid was degraded by magnetic fluid - modified cells (84-95%), while the efficiency of cell which were modified by other methods was much lower (40-60%). Thanks to immobilization on particles of magnetic chitosan, we made completely new type of magnetic material, which was tested for adsorption of Crystal violet and Safranin O. It was founded that magnetic chitosan adsorbs no dyes, so all adsorption belongs to immobilized yeast. The maximum adsorption capacities were determined using Langmuire isotherm at 69,4 mg/g for Crystal violet and 99,0 mg/g for Safranin O.
243

Efeito de alguns parâmetros de síntese na obtenção de copolímeros à base de estireno e divinilbenzeno com propriedades magnéticas / Effect of some synthesis parameters in the production of styrene and divinylbenzene based copolymers with magnetic properties

Thiago Alexandre de Oliveira Bouças 04 July 2008 (has links)
Nesta dissertação, microesferas poliméricas com propriedades magnéticas à base de estireno e divinilbenzeno foram sintetizadas por polimerização em suspensão. O material utilizado para conferir as propriedades magnéticas foi magnetita sintetizada em laboratório. Foram estudados os efeitos da modificação da magnetita com ácido oleico, da velocidade de agitação, do teor de iniciador e de teor de agente de suspensão sobre as características das partículas poliméricas obtidas. As microesferas foram caracterizadas quanto ao seu aspecto morfológico, à estabilidade térmica, ao tamanho e à distribuição do tamanho de partículas e quanto à suas propriedades magnéticas. Foram obtidos copolímeros com morfologia esférica e tamanho micrométrico, com propriedades magnéticas comparáveis a materiais superparamagnéticos. O tamanho de partícula foi afetado principalmente pela velocidade de agitação, enquanto que a distribuição deste tamanho foi fortemente influenciada pela alteração dos teores de iniciador e agente de suspensão. A magnetização de saturação para as microesferas ficou próxima dos valores encontrados na literatura, comparando-se resinas com o mesmo teor de material magnético. A modificação com ácido oleico foi considerada importante para a incorporação do material magnético / In this dissertation, polymeric microspheres with magnetic properties based on styrene and divinylbenzene were synthesized by suspension polymerization technique. In order to obtain magnetic properties, magnetite was synthesized in laboratory. The effects of magnetite modification with oleic acid, stirring velocity, concentration of initiator and concentration of stabilizer on the particles properties were studied. The magnetic microspheres were characterized according to morphology, thermal stability, particle size and its distribution and magnetic properties. It was verified that the microspheres presented spheric shape, micrometric size and magnetic properties comparable to superparamagnetic materials. Particle size was mainly affected by stirring velocity, while its dispersion was strongly affected by concentration of initiator and stabilizer. The saturation magnetization for the microshpheres was similar to the values reported in the literature, taking in account resins with the same content of magnetic material. The modification with oleic acid was considered important to the incorporation of the magnetic material
244

Preparação e caracterização de microesferas poliméricas com morfologia casca-núcleo e propriedades magnéticas à base de estireno e divinilbenzeno / Preparation and characterization of microspheres polymeric core-shell morphology and magnetic properties based on styrene and divinylbenzene

Washington Jose Fernandes Formiga 06 March 2012 (has links)
Coordenação de Aperfeiçoamento de Pessoal de Nível Superior / Foram sintetizadas microesferas poliméricas com propriedades magnéticas e morfologia casca-núcleo por meio da técnica de polimerização em suspensão em duas etapas. O núcleo foi constituído por poli(estireno-co-divinilbenzeno) e magnetita modificada com ácido oleico. Foi avaliada a influência da velocidade de agitação e da concentração de iniciador sobre as características das microesferas utilizadas como núcleo (morfologia, tamanho de partículas, propriedades magnéticas e estabilidade térmica). A casca foi constituída por poli(estireno-co-divinilbenzeno) sem material magnético. Foi avaliado o método de adição da emulsão dos monômeros formadores da casca e o tempo de inchamento dos núcleos na emulsão. As microesferas casca-núcleo foram caracterizadas quanto ao seu aspecto morfológico e à estabilidade térmica. Os núcleos não apresentaram ciclos de histerese, estando assim próximos de um material com propriedades superparamagnéticas. O copolímero sintetizado com a maior velocidade de agitação e a menor concentração de iniciador foi o que apresentou o maior teor de ferro incorporado (3,317 %), a maior magnetização de saturação (2,99 emu/g) e o menor diâmetro médio de partículas (81 m). As microesferas casca-núcleo apresentaram apenas um estágio de degradação e as suas Tmáx foram menores do que a do núcleo. O mapa composicional de ferro confirmou a presença de magnetita na superfície das microesferas casca-núcleo / Polymeric microspheres with magnetic properties and core-shell morphology were synthesized by the technique of suspension polymerization in two stages. The core was constituted by poly(styrene-co-divinylbenzene) and magnetite coated with oleic acid. The influence of stirring rate and initiator concentration on microspheres characteristics (morphology, particle size, magnetic properties and thermal stability) was studied. The shell was constituted by poly(styrene-co-divinylbenzene) without magnetic material. It was also evaluated the methods of the monomers emulsion addition and the coress swelling time in the emulsion.. The microspheres were characterized by morphologic aspect and thermal stability. The cores did not presented hysteresis cycles, thus proving the superparamagnetic properties. Copolymer synthesized with the higher stirring rate and lower initiator concentration presented the higher incorporated iron content (3.317 %), higher saturation magnetization (2.99 emu/g) and the lower average particle diameter (81 m). Core-shell microspheres presented only one stage of degradation and the Tmáx were smaller than temperature of the cores. Iron compositional map confirmed the presence of magnetite on the surface of core-shell microspheres
245

Synthèse et caractérisation de nanomatériaux hybrides innovants pour le biomédical / Synthesis and characterization of new hybrids nanomaterials for biomedical applications

Venturini, Pierre 15 December 2017 (has links)
Depuis quelques décennies, les nanomatériaux et tout particulièrement les nanoparticules d’oxyde de fer (magnétite/maghémite) superparamagnétiques ont connus un intérêt croissant en nano-médecine. Leur biocompatibilité et leurs propriétés magnétiques permettent notamment leur utilisation à des fins de diagnostic (IRM, Imagerie optique et nucléaire…) et de thérapie (Hyperthermie, nano vectorisation…). Au cours de cette thèse, la première étape a consisté à étudier en détails l’influence de plusieurs paramètres de synthèse sur les propriétés finales des nanoparticules d’oxyde de fer magnétique. Cette étude avait pour but de développer et d’optimiser une méthode de synthèse dérivée de la méthode de synthèse classique dite de co-précipitation mais modifiée par ajout de ligand citrates au cours de la synthèse. Des nanoparticules d’oxyde de fer d’une taille pouvant être contrôlée entre 4 et 13 nm recouvertes par une couronne de ligands citrates ont ainsi été synthétisées, celles-ci présentent une aimantation à saturation atteignant jusqu’à 75 emu/g d’oxyde de fer qui est une valeur particulièrement haute pour des nanoparticules de cette taille. Tout au long de ce travail, la caractérisation de ces nanoparticules par un panel étendu de techniques (MET, DRX, Mössbauer, IRTF, XPS, mesures magnétiques, DLS …) à permis notamment d’étudier de façon précise les relations existantes entre la taille, le taux de ligand, la composition et les propriétés magnétiques des nanoparticules synthétisées. Ces nanoparticules fonctionnalisées par des citrates ont ensuite été testées en milieu biologique afin d’évaluer leur internalisation dans les cellules et leur cytotoxicité. Dans un deuxième temps, d’autres travaux ont été menés sur les nanoparticules d’oxyde de fer. Notamment le remplacement des ligands citrates par un polymère bio-inspiré pouvant, selon les fonctions chimiques qui lui sont adjointes, avoir de multiples applications dans le domaine biomédical / From decades now, nanomaterials and especially superparamagnetic iron oxide nanoparticles are studied for their numerous applications in nanomedecine area. The biocompatibility and the magnetic properties of such nano-objects allow their utilization for diagnostic (MRI, optical imagery, PET…) and for therapy application (nanovectorization, hyperthermia…) During this thesis work, the first step was to study the influence of several synthesis parameters on the final properties of the magnetic iron oxide nanoparticles. The aim of this study was the development and the optimization of the widely used way of synthesis by co-precipitation modified by a ligand addition during the growth step of the synthesis. Citrate capped iron oxide nanoparticles with a controlled size between 4 and 13 nm have been synthesized, the saturation magnetization of these nanoparticles reach 75 emu/g of iron oxide, this value is particularly high for nanoparticles of such sizes. During this work, the large panel of characterizations performed on these nanoparticles (TEM, XRD, Mössbauer, FTIR, XPS, DLS, Magnetic measurement) allowed to study precisely the relations between size, ligand ratio, composition and magnetic properties of the synthesized nanoparticles. The interaction between the synthesized citrate capped nanoparticles and biological materials such as human cells have been investigated in-vitro notably to evaluate cells internalization and citotoxicity. In a second step, some additional works have been performed on the citrate capped iron oxide nanoparticles in order to replace the citrate ligand by a bio-inspired polymer (poly-oxazoline). This polymer can have multiple biomedical applications depending of the pendent chemical groups that have been fixed on it
246

Désaimantation induite par impulsions laser femtosecondes dans des nanostructures d'oxyde de fer / Femtosecond laser-induced demagnetization in iron oxide nanostructures

Terrier, Erwan 08 July 2016 (has links)
Ce travail de thèse traite de la dynamique ultrarapide de spins et de charges dans des oxydes de fer. Dans un premier temps, on montre à l'aide d'un montage pompe-sonde résolu en temps et exploitant l'effet Faraday magnéto-optique, que le temps de désaimantation dans une assemblée de nanoparticules de maghémite est plus rapide que le temps de désaimantation dans une assemblée de nanoparticules de magnétite. Une superposition des temps de thermalisation des électrons et de désaimantation est observée dans la maghémite. Cette accélération du temps de désaimantation est interprétée comme étant la conséquence d'un renforcement des interactions antiferromagnétiques dans la maghémite. La seconde partie prouve qu'il est possible de caractériser la transition de Verwey dans un film de magnétite grâce à des signaux de dynamique de charges et de spins. La dynamique ultrarapide d'aimantation se caractérise par un mouvement de précession dépendant de la température. D'importantes modifications des oscillations sont visibles de part et d'autre de la température de Verwey, reflétant un changement d'anisotropie caractéristique de cette transition. / This work deals with spins and charges ultrafast dynamics in iron oxide. Thanks to a time-resolved magneto-optical Faraday effect measurements, we show the demagnetization time in an assembly of maghemite nanoparticles is faster than the demagnetization time in an assembly of magnetite nanoparticles. A superposition of thermalization times of electron and demagnetization times is observed in maghemite. This acceleration of the demagnetization time is interpreted as the effect of an enhancement of antiferromagnetic interactions in maghemite. The second part demonstrates the possibility to characterize the Verwey transition in a thin film of magnetite thanks to charges and spins dynamics signals. The ultrafast magnetization dynamic shows a temperature-dependent precession motion. Huge modifications of oscillations are visible on both side of Verwey temperature, reflecting an anisotropy change typical of this transition.
247

Efeito de alguns parâmetros de síntese na obtenção de copolímeros à base de estireno e divinilbenzeno com propriedades magnéticas / Effect of some synthesis parameters in the production of styrene and divinylbenzene based copolymers with magnetic properties

Thiago Alexandre de Oliveira Bouças 04 July 2008 (has links)
Nesta dissertação, microesferas poliméricas com propriedades magnéticas à base de estireno e divinilbenzeno foram sintetizadas por polimerização em suspensão. O material utilizado para conferir as propriedades magnéticas foi magnetita sintetizada em laboratório. Foram estudados os efeitos da modificação da magnetita com ácido oleico, da velocidade de agitação, do teor de iniciador e de teor de agente de suspensão sobre as características das partículas poliméricas obtidas. As microesferas foram caracterizadas quanto ao seu aspecto morfológico, à estabilidade térmica, ao tamanho e à distribuição do tamanho de partículas e quanto à suas propriedades magnéticas. Foram obtidos copolímeros com morfologia esférica e tamanho micrométrico, com propriedades magnéticas comparáveis a materiais superparamagnéticos. O tamanho de partícula foi afetado principalmente pela velocidade de agitação, enquanto que a distribuição deste tamanho foi fortemente influenciada pela alteração dos teores de iniciador e agente de suspensão. A magnetização de saturação para as microesferas ficou próxima dos valores encontrados na literatura, comparando-se resinas com o mesmo teor de material magnético. A modificação com ácido oleico foi considerada importante para a incorporação do material magnético / In this dissertation, polymeric microspheres with magnetic properties based on styrene and divinylbenzene were synthesized by suspension polymerization technique. In order to obtain magnetic properties, magnetite was synthesized in laboratory. The effects of magnetite modification with oleic acid, stirring velocity, concentration of initiator and concentration of stabilizer on the particles properties were studied. The magnetic microspheres were characterized according to morphology, thermal stability, particle size and its distribution and magnetic properties. It was verified that the microspheres presented spheric shape, micrometric size and magnetic properties comparable to superparamagnetic materials. Particle size was mainly affected by stirring velocity, while its dispersion was strongly affected by concentration of initiator and stabilizer. The saturation magnetization for the microshpheres was similar to the values reported in the literature, taking in account resins with the same content of magnetic material. The modification with oleic acid was considered important to the incorporation of the magnetic material
248

NanobiocompÃsitos superparamagnÃticos para aplicaÃÃo como antenas ressoadoras dielÃtricas / Superparamagnetic nanobiocomposites for application as dielectric resonator antennas

Andrà Leandro da Silva 14 August 2014 (has links)
nÃo hà / à crescente o interesse mundial pelo desenvolvimento de tecnologias chamadas âverdesâ que possibilitem o uso de produtos com menor impacto ao meio ambiente, assim como tambÃm se fortalecem as polÃticas de incentivo ao aproveitamento mÃximo e sustentÃvel dos recursos naturais. O principal objetivo desse estudo foi desenvolver nanobiocompÃsitos superparamagnÃticos para aplicaÃÃo como antenas ressoadoras dielÃtricas. Para tal, um plÃstico termorrÃgido biobaseado foi preparado utilizando o cardanol em alternativa aos fenÃis petroquÃmicos. Esse plÃstico termorrÃgido foi utilizado como matriz para o preparo de biocompÃsitos, utilizando 15% em massa de fibra de bucha bruta e tambÃm modificada por tratamento quÃmico (NaOH 5, 10 e 15% e NaClO 1%) como fase dispersa. Para o preparo dos nanobiocompÃsitos, alÃm da fibra de bucha, nanopartÃculas de magnetita, sintetizadas pelo mÃtodo da coprecipitaÃÃo, foram impregnadas no plÃstico termorrÃgido em diferentes teores de 1, 5 e 10% em massa. TÃcnicas de Termogravimetria (TG), Calorimetria exploratÃria diferencial (DSC), AnÃlise dinÃmico-mecÃnica (DMA), Microscopia eletrÃnica de varredura (MEV), Microscopia Ãptica, Microscopia eletrÃnica de transmissÃo (MET), DifraÃÃo de raios X (DRX), Espectroscopia no infravermelho com transformada de Fourier (FTIR), Espectroscopia MÃssbauer, Ensaios de resistÃncia à traÃÃo, Medidas dielÃtricas, Magnetometria de amostra vibrante (VSM) e BiodegradaÃÃo em solo simulado foram utilizadas para caracterizaÃÃo. Os resultados mostraram que o tratamento alcalino melhorou a estabilidade tÃrmica e o Ãndice de cristalinidade da fibra de bucha. O agente reticulador utilizado (DETA) mostrou-se eficiente, possibilitando a cura completa dos materiais. Os biocompÃsitos com fibra tratada apresentaram maior estabilidade tÃrmica, resistÃncia à traÃÃo superior e melhor Ãndice de biodegradaÃÃo em relaÃÃo ao biocompÃsito com fibra natural. A magnetita sintetizada exibiu tamanho nanomÃtrico, alÃm de alta pureza, alta cristalinidade e carÃter superparamagnÃtico. Todos os nanobiocompÃsitos exibiram superparamagnetismo e mostraram excelente estabilidade tÃrmica, boas taxas de biodegradaÃÃo e melhor resistÃncia mecÃnica para o material com 10% de magnetita. Todas as antenas ressoadoras dielÃtricas preparadas apresentaram perda de retorno satisfatÃria e, portanto, adequaÃÃo para fins comerciais e tecnolÃgicos, com maior potencial para atuaÃÃo em banda larga. / There is a growing global interest for the development of green technologies that allow the use of products with less damage to environment, as well as for maximum and sustainable use of natural resources. The main aim of this study was to develop superparamagnetic nanobiocomposites for application as dielectric resonator antennas. For this purpose, a biobased thermoset plastic was prepared by using cardanol as an alternative to petrochemical phenol. This thermoset plastic was used as a polymer matrix and biocomposites were prepared by using 15 wt% of untreated and modified sponge gourd fibers by chemical treatment (NaOH 5, 10, and 15 wt% and NaClO 1 wt%) as dispersed phase. For the nanobiocomposites preparation, besides the sponge gourd fibers insertion, the thermoset plastic were also impregnated with magnetite nanoparticles in different contents (1, 5, and 10 wt%). Techniques of Thermogravimetry (TG), Differential Scanning Calorimetry (DSC), Dynamic Mechanical Analysis (DMA), Scanning Electron Microscopy (SEM), Optical Microscopy, Transmission Electron Microscopy (TEM), X-ray Diffraction (XRD), Fourier Transform Infrared Spectroscopy (FTIR), MÃssbauer Spectroscopy, Tensile testing, Dielectric measurements, Vibrating Sample Magnetometry (VSM) and Biodegradation in simulated soil were performed for characterization. The results showed that alkaline treatment improved the thermal stability and the crystallinity index of the sponge gourd fiber. The crosslinking agent used (Diethylenetriamine) was efficient and enabled complete cure for all materials. The biocomposites reinforced by treated fiber showed better thermal stability, superior performance in Tensile testing and greater biodegradation rates, when compared to the biocomposite reinforced by raw fiber. The magnetite particles exhibited nanometric size, high purity and crystallinity, and superparamagnetic character. All nanobiocomposites showed superparamagnetic behavior, excellent thermal stability, good biodegradation rates, and better mechanical strength for the material with magnetite 10 wt%. All dielectric resonators antennas exhibited satisfactory return loss and suitability for commercial and technological applications, especially for performance in broadband.
249

Metal oxide synthesis and its application in the heterogeneous catalytic oxidation processes, using H2O2 or peroxydisulfate as oxidant / Propriétés de nanostructures d'oxydes de métaux de transition pour les procédés avancés d'oxydation dans l'eau, en présence de peroxyde d'hydrogène et de peroxydisulfate comme oxydant

Hou, Liwei 13 September 2013 (has links)
Parmi les procédés avancés d'oxydation (AOPs), les procédés de type Fenton (réactif de Fenton: Fe2+/H2O2) et les procédés d'oxydation par le persulfate, sont décrits comme des procédés très performants. Le procédé Fenton est une voie prometteuse et attractive pour le traitement d'une large variété de composés organiques polluants, difficiles à traiter par les voies classiques de dépollution. Au cours du procédé Fenton, des radicaux hydroxyles, molécules à fort pouvoir oxydant capable de réagir avec pratiquement tous types de composés organiques et inorganiques, sont générés. De même, du fait de la structure similaire entre H2O2 et les ions peroxydisulfate, ces derniers peuvent se décomposer en radicaux sulfates (SO4-•), un autre type d'oxydant hautement réactif pouvant réagir avec les composés organiques. Cependant, les procédés Fenton et d'activation du peroxydisulfate classiques présentent plusieurs inconvénients. En effet, la solution doit être acidifiée avant la réaction, et des procédés complexes de purification / séparation sont nécessaires après réaction. Afin de contourner ces inconvénients, le développement de procédés de traitement hétérogènes est proposé pour le traitement de l'eau. Dans cette optique de développement de procédés économes, les oxydes de fer comme la magnétite sont proposés comme remplaçants des sels solubles de fer. Une utilisation de tels matériaux, à l'état solide, présente des avantages indéniables, dont la séparation aisée de l'espèce active après réaction par sédimentation ou filtration. Dans le cadre de ce travail de doctorat, différents types d'oxydes de fer, hématite ou magnétite, ont été synthétisés en milieu liquide ionique. La morphologie, les propriétés structurales, les rapports de surface FeII/FeIII, les surfaces spécifiques, les tailles de domaine cristallin, etc. ont été évaluées. Deux molécules différentes, la tétracycline (TC) et le phenol, couramment utilisées dans l'industrie chimique, ont été sélectionnées comme polluants modèles afin d'évaluer les performances des matériaux préparés pour leur élimination. Une partie importante du travail de doctorat a donc été l'étude des propriétés des matériaux pour l'élimination de polluants organiques par le procédé Fenton hétérogène. Les résultats montrent clairement que les principaux facteurs affectant les performances du procédé sont reliés aux propriétés de la phase active, du fait du caractère surfacique des réactions. La stabilité des systèmes catalytiques préparés est néanmoins une propriété cruciale également étudiée. Le manuscrit de doctorat met donc l'accent sur la conception de matériaux originaux destinés à une utilisation dans les procédés avancés d'oxydation dans l'eau. / Fenton reaction (Fenton reagent: (Fe2+/H2O2)) and persulfate oxidation process, as advanced oxidation processes, are powerful oxidations used world around. Fenton reaction has been evidenced to be a promising and attractive treatment method for the degradation of a wide variety of hazardous organic pollutants, which are difficult to be treated using traditional soft treatment technologies. During Fenton process, free hydroxyl radicals (HO•), strong oxidant molecules capable of reacting with practically all types of organic and inorganic compounds, are generated. In the meanwhile, due to the similar structure between H2O2 and peroxydisulfate ions, peroxydisulfate ions can be decomposed to sulfate radicals (SO4-•), another kind of highly active oxidant that can react with organic compounds. However, the classical Fenton or peroxydisulfate activation processes present some disadvantages. Indeed, the solution needed acidification before carrying out the reaction and complex separation processes have to be applied after reaction. To overcome these drawbacks, heterogeneous catalytic oxidation processes were introduced for wastewater treatment. In this line, magnetite was evidenced as potential substituent to soluble iron ions, and it offers significant advantages such as an easy separation after reaction since the active material can be easily recovered by sedimentation or filtration for further used. In this PhD work, iron oxides, hematite and magnetite, were synthesized using an ionic liquid mediated process. The morphology, structural properties, FeII/FeIII surface ratios, specific surface areas (SSA), mean particle diameters, site densities, etc. were evaluated. Two different model pollutants (tetracycline (TC) and phenol), which are widely used chemicals all over the world, were selected to evaluate the performance of the prepared active materials. A significant part of the PhD study was then on the study of heterogeneous Fenton-like reaction for phenol and TC degradation. Experiments showed that the main factors affecting the heterogeneous Fenton-like system are related to the heterogeneous active phase properties, due to the surface reaction nature occurring over iron oxide surface. However, stability of this active phase, with progressive dissolution under reaction, is also a real challenge. This PhD manuscript, focusing on the design of highly active materials for advanced oxidation processes (AOPs), is constituted of five experiment result parts.
250

Matrices thermodurcissables époxydes et furaniques biosourcées – conception d’assemblages macromoléculaires / Advanced bio-based epoxies and furanics thermosets – hierarchically assembled macromolecular design

Pin, Jean-Mathieu 15 June 2015 (has links)
Le travail de recherche présenté dans cette thèse s’est orienté vers l’élaboration de matériaux avancés et la conception de polymères/composites biosourcés. Ce dernier sujet a été entrepris à travers la combinaison de différentes matières premières biosourcées qui sont connues comme ayant un grand potentiel de substitution des monomères pétrosourcés. Tout d’abord, un travail fondamental a été exécuté en combinant l’huile de lin epoxydée (ELO) avec des dérivés d’anhydrides d’acides comme agents de réticulation, afin de relier la réactivité chimique de polymérisation à la structure du réseau formé et aux propriétés thermomécaniques. Afin de devenir économiquement viable, les bio-raffineries doivent urgemment valoriser les sous-produits issus de la conversion de la biomasse. Fort de ce constat, une deuxième étude sur l’incorporation et la copolymérisation d’une quantité importante d’humins (résidu hétérogène obtenu durant la conversion des sucres en hydroxymethylfurfural (HMF)) avec de l’alcool furfurylique (FA) a été réalisée avec succès afin de créer de nouvelles résines thermodures. Une autre voie proposée consiste en la combinaison de ELO et de FA à travers une polymérisation cationique, dans l’idée de créer de nouvelles résines totalement biosourcées, générant ainsi une gamme de matériaux aux propriétés mécaniques modulables. / The research work presented in this thesis was oriented on advanced thermoset materials and also on the conception of bio-based polymers and composites. This last topic has been investigated by the combination of different bio-based raw materials which are well-known to have a great potential to substitute the petroleum monomers. Firstly, a fundamental work has been done on the combination of epoxidized linseed oil (ELO) and anhydrides as cross-linkers, which links the polymerization reactivity with the network structure and thermomechanical properties. For being economically realistic, the bio-refineries are urged to valorize the sidestream products issued from biomass conversion. In that respect, a second study investigated successfully the incorporation and copolymerization of an important amount of humins (heterogeneous residues obtained during the sugar conversion into hydroxymethylfurfural (HMF)) with furfuryl alcohol (FA) in order to create new resins. Another proposed combination, focused on ELO and FA cationic copolymerization with the purpose to create new fully bio-based resins with tailored mechanical properties. Concerning the elaboration of advanced polymers and composites, a reflection around the hierarchically organized natural materials has been achieved in order to adapt the self-organization and structuration concepts to polymeric network.

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