In this study, the photocatalytic mineralization of the industrial dump-site leachate was evaluated using an internally-irradiated 18-Litre pilot-scale aerated annular bubble column photoreactor. The study includes evaluating the effect of catalyst loading, leachate initial concentration, initial solution pH, light intensity and oxygen partial pressure. The reaction runs were performed over a 48-hours period at room temperature and atmospheric pressure. Titanium catalyst loading was optimized to be 3 gL-1 where the reaction rate constant 20x10-6 mol L-1 min-1.Beyond this dosage, the effect of light scattering by the catalyst particles were noticed on dropping the degradation rate. Moreover, at high catalyst loading, particles aggregates reduce the interfacial area between the reaction solution and the photocatalyst resulting in significant reduction in the number of active sites on the catalyst surface. It is also noticed that when the initial leachate concentration is high, the number of the active sites are decreased because of their competitive adsorption on the TiO2 particles; while on the other hand, during the light intensity illumination period, the OH radicals formed on the catalyst surface are remaining constant as evidenced by constant hydroxyl production rate. Thus, the reactive O2 attacking the contaminants molecules decrease and simultaneously the overall photodegradation efficiency also decrease dramatically. The plot of the apparent reaction rate constant versus the initial leachate concentration exhibits almost a quadratic behaviour which has an optimum value at concentration of 50 mM. Finally, it was found that the degradation rate constant increased with O2 partial pressure until a maximum was obtained around 50% O2/N2 of gas feed composition. The drop in the rate beyond 50% can be explained by the fact that the dissolved oxygen molecular oxygen is strongly electrophilic and thus increasing the dissolved oxygen content probably reduced electron-hole recombination rate and hence the system was able to maintain favourable charge balance necessary for the photocatalytic-redox process. Moreover, in the presence of excess O2, the photocatalyst surface may become highly hydroxylated to the point of inhibiting the adsorption of organic species causing decrease in the degradation rate. Effect of upflow co-current and counter current continuous operation mode were performed in the 18-litre bubble column photoreactor for the photooxidation degradation tratment of the dump-site landfill leachate. The best situation is liquid flow rate at 800 mL min-1 and total gas flow rate at 5 Lmin-1 for the counter current operation, while for the up-flow co-current operation, the best situation is liquid flow rate at 600 mL min-1 and total gas flow rate at 5 Lmin-1

Photocatalysis is a green technology that has been widely used in wastewater treatment. In this work, mass transfer processes in corrugated photocatalytic reactors were characterized both experimentally and through computer simulations. For the experimental work, various drum rotational speeds, reactor liquid volumes and number of corrugations were studied to elucidate their effects on mass transfer phenomena. The mass transfer rate was found to increase with increasing rotational speed. Liquid volumes in the reactor significantly affect the mass transfer rate when 20% of the surface area of the drum was immersed. A higher mass transfer rate was found using the drum with 28 corrugations, which had the lowest mass transfer coefficient when compared to the drums with 13 and 16 corrugations. In the computer simulations, velocity and concentration fields within the corrugated reactors were modelled to explore the characteristics of mass transfer processes. The mass transfer coefficients predicted by the simulations were lower than those measured experimentally due to mass transfer limitations occurring between the corrugation volume and bulk solution in the simulations. Based on mass transfer characteristics, it was determined that the drum with 28 corrugations was the most efficient photocatalytic reactor, and had the lowest mass transfer coefficient among those studied.

The basis of prosperity of 20th centrury is oil. As oil is going to be used up, people need to find alternatives to meet the earth’s energy demand in 21st centrury. For each second, there are about 1.2×1017 J energy hitting the earth. The energy in 1 hour of sunlight is about 4.32×1020 J, which almost meets the energy consumed on earth in 2016. It determines solar energy may be a potential candidate to solve the energy crisis. As for techniques to utilize solar energy, the most popular one is using photovoltaic (PV) cells. PV cell is a device to convert solar energy into electricity. There are also some other techniques trying to utilize solar energy. Photocatalysis is one of them, which is to convert solar energy into chemical energy. Applications of photocatalysis have extended from hydrogen evolution via water splitting to environemtnal remediation, CO2/ N2 reduction and so on. Photocatalysis, as an advanced oxidation process, has been extensively studied and applied to the purification and remediation of contaminated water and wastewater, and exhibits advantages over conventional treatment technologies. When considering solar energy as an energy source for photocatalysis, it is key to prepare visible light-responsive materials. Bismuth-based semiconductors are promising materials as visible light-responsive photocatalysts primarily due to their suitable band gaps, well-dispersed valence bands, and commercial availabilities at reasonable costs, as well as the possibility of preparing them under mild conditions. Recent work focusing on the preparation, characterization and activity testing of bismuth-based photo-active materials as well as their associated photoreactor designs are introduced herein. In order to enhance the photocatalytic activities of the new materials, different precursors, additives, preparation procedures and process parameters, as well as surface treatments were explored to obtain binary and ternary heterostructures, with different doping, surface modification, nanoparticle sizes and morphologies. It was found that formation of heterojunction and loading metal nanoparticle on the surface are very effective to imrove the photocatalytic activity of the support. In this work, we found that palladium nanoparticles modified BiVO4 exhibited excellent activity in the decomposition of phenol, which was even higher than TiO2. To facilitate the separation process of catalysis particels from a slurry system, magnetically separable composites were also prepared, and it was found that it is very effective to remove the particles from the slurry system using external magnets. To further scale up this process, two different types of immbolized photoreactors (flat-plate and packed beads photoreactor) were also developed. Suggestions were made for further work in this research area.

Photocatalysis is a green technology that has been widely used in wastewater treatment. In this work, mass transfer processes in corrugated photocatalytic reactors were characterized both experimentally and through computer simulations. For the experimental work, various drum rotational speeds, reactor liquid volumes and number of corrugations were studied to elucidate their effects on mass transfer phenomena. The mass transfer rate was found to increase with increasing rotational speed. Liquid volumes in the reactor significantly affect the mass transfer rate when 20% of the surface area of the drum was immersed. A higher mass transfer rate was found using the drum with 28 corrugations, which had the lowest mass transfer coefficient when compared to the drums with 13 and 16 corrugations. In the computer simulations, velocity and concentration fields within the corrugated reactors were modelled to explore the characteristics of mass transfer processes. The mass transfer coefficients predicted by the simulations were lower than those measured experimentally due to mass transfer limitations occurring between the corrugation volume and bulk solution in the simulations. Based on mass transfer characteristics, it was determined that the drum with 28 corrugations was the most efficient photocatalytic reactor, and had the lowest mass transfer coefficient among those studied.

Pour relever le défi énergétique du 21 ième siècle, une solution consiste à mettre au point des procédés solaires de production de vecteurs énergétiques par photosynthèse artificielle permettant la synthèse photo-catalytique de carburants solaires. L’obtention de performances cinétiques et énergétiques élevées pour ces procédés nécessite le développement d’outils de conception optimale tels des modèles de connaissance robustes et prédictifs considérant le transfert de rayonnement comme processus physique contrôlant le procédé à plusieurs échelles. Une chaine prédictive de modélisation, avec ses différents maillons, a donc été développée, mise en œuvre et validée sur une réaction modèle de photo-production d’hydrogène à partir d’une suspension de particules de CdS. Ainsi, à partir de leurs caractéristiques (taille, forme...) et de leurs propriétés optiques, les propriétés radiatives des particules, à savoir sections efficaces d’absorption, de diffusion et fonction de phase ont été calculées au moyen de la théorie de Lorenz-Mie et validées par des mesures de transmission sur un banc optique de précision. Ces paramètres ont ensuite été utilisés comme données d’entrée pour la résolution de l’équation de transfert radiatif, effectuée au moyen de la méthode de Monte Carlo. L’accord entre transmissions prédite et expérimentale, tenant compte éventuellement de la diffusion du rayonnement par les bulles d’hydrogène, est bon dans la bande spectrale absorbée. En parallèle, l’utilisation d’un équipement complet et d’une chaine d’acquisition de mesures autour d’un petit photoréacteur d’étude, pour lequel les densités de flux incidentes ont été validées par actinométrie, a permis d’obtenir des résultats expérimentaux de haute précision en photo-production d’hydrogène. Un premier modèle de couplage thermocinétique original a alors été formulé, validé après identification d’un seul paramètre agrégé, dont la réification sera abordée ultérieurement, et utilisé de façon prédictive avec succès. Ce travail ouvre de très nombreuses perspectives de recherche, il a ainsi permis de vérifier la possible transposition à la photosynthèse artificielle de la chaine prédictive de modélisation multi-échelles et donne des pistes quant à l’optimisation cinétique et énergétique des photo-procédés produisant des carburants solaires. / To address the energy challenge of the 21 st century, a solution is the development of solar processes for the production of energy vectors by artificial photosynthesis, in particular photocatalytic synthesis of solar fuels. However high kinetic and thermodynamic performances for these processes must be reached, this requires the development of tools for optimal design, including predictive knowledge models addressing radiative transfer that is the controlling physical process at different scales. A predictive multi-scale model has therefore been developed, implemented and validated on a simple reaction for hydrogen photo-production from CdS particle slurry. On the basis of their characteristics (size, shape, etc.) and their optical properties, the radiative properties of the particles, namely absorption and scattering cross sections and phase function, were calculated using the Lorenz-Mie theory and validated by measurements of transmittances on a high accuracy optical bench. These parameters were then used as input parameters to solve rigorously the radiative transfer equation with the Monte Carlo method. The agreement between predicted and experimental transmittance, taking into account light scattering by hydrogen bubbles, is good in the absorbed spectral band. In parallel, the use of complete experimental bench centered on a small photoreactor, where incident flux densities have been validated by actinometry, yielded high accuracy hydrogen photo-production results. A first and original model of thermokinetic coupling was then formulated and validated after identification of a single lumped parameter whose reification will be approached later and used predictively with success. This work opens up a large number of research prospects because it makes possible to transpose the predictive chain to artificial photosynthesis. This work provides also guidance on the kinetic and thermodynamic optimization of photo-processes producing solar fuels.

Les sulfilimines et les sulfoximines sont des motifs structuraux dont l’intérêt synthétique est grandissant, notamment du fait de leurs applications en chimie médicinale et en agrochimie. Les travaux rapportés dans cet ouvrage décrivent le développement de nouvelles méthodes de synthèse efficaces pour la production de ces unités atypiques. Ces méthodes sont basées sur la réactivité d’une source d’azote électrophile, vis-à-vis de thioéthers et de sulfoxydes. L’utilisation d’un complexe métallique introduit en quantité catalytique a permis de favoriser le processus réactionnel. En tirant bénéfice de l’expertise de notre groupe de recherche sur le développement de réactions d’amination stéréosélectives de liaisons C-H et d’aziridination de styrènes, nous avons d’abord étudié la réactivité des N-mésyloxycarbamates comme source d’azote électrophile. Après avoir optimisé sa synthèse sur grande échelle, ce réactif chiral a été utilisé dans des réactions d’amination de thioéthers et de sulfoxydes, catalysées par un dimère de rhodium (II) chiral. Un processus diastéréosélectif efficace a été mis au point, permettant de produire des sulfilimines et des sulfoximines chirales avec d’excellents rendements et sélectivités. Au cours de l’optimisation de cette méthode de synthèse, nous avons pu constater l’effet déterminant de certains additifs sur la réactivité et la sélectivité de la réaction. Une étude mécanistique a été entreprise afin de comprendre leur mode d’action. Il a été observé qu’une base de Lewis telle que le 4-diméthylaminopyridine (DMAP) pouvait se coordiner au dimère de rhodium(II) et modifier ses propriétés structurales et redox. Les résultats que nous avons obtenus suggèrent que l’espèce catalytique active est un dimère de rhodium de valence mixte Rh(II)/Rh(III). Nous avons également découvert que l’incorporation de sels de bispyridinium avait une influence cruciale sur la diastéréosélectivité de la réaction. D’autres expériences sur la nature du groupe partant du réactif N-sulfonyloxycarbamate nous ont permis de postuler qu’une espèce nitrénoïde de rhodium était l’intermédiaire clé du processus d’amination. De plus, l’exploitation des techniques de chimie en débit continu nous a permis de développer une méthode d’amination de thioéthers et de sulfoxydes très performante, en utilisant les azotures comme source d’azote électrophile. Basée sur la décompositon photochimique d’azotures en présence d’un complexe de fer (III) simple et commercialement disponible, nous avons été en mesure de produire des sulfilimines et des sulfoximines avec d’excellents rendements. Le temps de résidence du procédé d’amination a pu être sensiblement réduit par la conception d’un nouveau type de réacteur photochimique capillaire. Ces améliorations techniques ont permis de rendre la synthèse plus productive, ce qui constitue un élément important d’un point de vue industriel. / Sulfilimines and sulfoximines are interesting building blocks that have found many applications both in medicinal chemistry and agrochemistry. During our work, we have developed new efficient methods for the synthesis of these moieties. A catalytic amount of metal complex is used to enhance the reactivity of an electrophilic nitrogen source towards thioethers and sulfoxides. Our group has developed an expertise in the development of stereoselective C-H bond amination and aziridination reactions using chiral N-mesyloxycarbamate as electrophilic amination reagents. The large scale synthesis of the chiral reagent was first investigated. It was then tested in a diastereoselective dirhodium(II)-catalyzed amination of thioethers and sulfoxides, to produce respectively chiral sulfilimines and sulfoximines in excellent yields and selectivities. During the optimization process, we have found that some additives proved instrumental to enhance both the reactivity and the selectivity of the reaction. Mechanistic studies has been carried out to elucidate the exact role of the additives. We have observed that Lewis bases, namely 4-dimethylaminopyridine (DMAP), can coordinate to a rhodium(II) dimer catalyst, modifying its structural and redox properties. These studies suggest that a mixed-valent dirhodium Rh(II)/Rh(III) complex is the catalytically active species in the thioether amination process. Moreover, we have discovered that the use of bispyridinium salts is crucial to enhance the selectivity of the amination reaction. Diastereoselectivities were also influenced by the nature of the leaving group of the N-sulfonyloxycarbamate. Based on the results, we hypothetized a rhodium nitrenoïd species as key intermediate in the amination process. Continuous flow techniques were employed in the development of a very efficient amination process of thioethers and sulfoxides, using azides as electrophilic amination reagents. Based on the photochemical decomposition of azide derivatives with a simple and commercially available iron(III) complex, we were able to produce sulfilimines and sulfoximines in excellent yields. We investigated the design of a new type of capillary photoreactor to further reduce the residence time of the amination process. The technical improvements were pivotal to enhance the efficiency and productivity of the reaction process.

This thesis deals with the study of UV-photochemical generation of volatile compounds (UV-PVG) in connection with atomic absorption spectrometry (AAS). Selenium (Se(IV)) was selected as a model analyte and many experiments were carried out to expand the current sum of knowledge of the topic. The study was commenced by assembling the UV-PVG apparatus in the continuous flow mode. The detection method used was AAS with externally heated quartz furnace atomizer. The focus of the first step of the study was on the construction of the volatile compounds generator (UV-photoreactor) with emphasis on the material used; tubes made of teflon or quartz of different diameters were tested. The construction of the apparatus was followed by optimization of the reaction conditions (the type and concentration of the photochemical agent and other agents, which increase the analytical signal; the carrier gas and the auxiliary hydrogen gas flow rate; the sample flow rate). Eventually, the analytical figures of merit of the selenium determination using the proposed method were found. The results showed that teflon reaction tubes are a good competitor to those made of quartz. The accuracy of the method has been successfully verified by analysis of certified reference material and its applicability has been further tested...