Made available in DSpace on 2017-07-10T18:08:20Z (GMT). No. of bitstreams: 1 Andreine Aline Roos.pdf: 2960540 bytes, checksum: 99bd1c80529add7a7c94dc586e17b240 (MD5) Previous issue date: 2013-02-22 / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior / Environmental contamination is a serious problem in today's society and for years aroused the interest of researchers. The pollutants with pharmacological activity are worrying the scientific community by increasing detection of these aquatic environments at concentrations ranging from µ L-1 to ng L-1, which are resistant to conventional treatments used in sewage treatment plants. Thus, it becomes necessary to investigate more effective treatments to minimize environmental contamination. The Advanced Oxidation Processes have attracted interest as promising treatments for removal of organic pollutants, among which stands out the heterogeneous photocatalysis whose the main drawback is the difficulty of separating the catalyst from solution degraded. To try to solve the problem, this work proposes the use of cellulose acetate/TiO2 composite and zinc metal plate coated with ZnO as catalysts for photodegradation of sulfamethoxazole. The composite was prepared by phase inversion of a solution of cellulose acetate and titanium tert-butyl orthotitanate that resulted in a composite with around 4% (in mass %) if TiO2.This composite proved not to be efficient in the degradation of sulfametoxazol in the presence of hydrogen peroxide under both, sunlight or artificial radiation. For this reason the continuity of the work occurred only with zinc plate coated with ZnO obtained by hydrothermal method. The 22 factorial experimental design, with triplicate on central point showed that the model was valid, and that the process was favored with increasing amounts of H2O2 at acidic pH. The equilibrium time for the photodegradation of sulfametoxazol using a plate Zn/ZnO was 120 minutes with removal of 95%, under artificial radiation, obeying the rate law of peudo-first order. The COD and nitrate concentration indicated that there was a small mineralization of the pollutant, despite the high removal, showing that there was probably the formation of intermediate species. Furthermore, the Zn/ZnO showed a catalytic efficiency almost unchanged up to 10 repetitions of photodegradation. However, at the end of the process the zinc concentration in the sample was above the allowed degraded by environmental agencies, necessitating the use of a post-treatment for removal of zinc or use of sulfametoxazol solution with pH closer to neutrality to avoid dissolution of the metal catalyst. / A contaminação ambiental é um grave problema da sociedade atual e há anos desperta o interesse dos pesquisadores. Os poluentes com atividade farmacológica vêm preocupando a comunidade científica pela crescente detecção dos mesmos em ambientes aquáticos, em concentrações que variam de µg L-1 a ng L-1, os quais são resistentes aos tratamentos convencionais empregados nas estações de tratamento de esgoto. Dessa forma, torna-se necessário a investigação de tratamentos mais eficientes para minimizar a contaminação ambiental. Os Processos Oxidativos Avançados vêm despertando interesse como tratamentos promissores para remoção de poluentes orgânicos, dentre os quais destaca-se a fotocatálise heterogênea, cujo principal empecilho é a dificuldade de separação do catalisador da solução degradada. Para tentar solucionar o problema, o trabalho propõe a utilização de catalisadores diferenciados como, compósito acetato de celulose/TiO2 e uma placa de zinco metálico recoberto com ZnO para a fotodegradação do princípio ativo sulfametoxazol. Contudo, o compósito acetato de celulose/ TiO2 não apresentou a eficiência similar ao TiO2 como era esperado, e assim optou-se por prosseguir os estudos de fotocatálise heterogênea utilizando a placa de zinco recoberta com ZnO como catalisador. O planejamento experimental fatorial, 22 com triplicata no ponto central, mostrou que o modelo utilizado foi válido, e que o processo é favorecido com quantidades maiores de H2O2 em pH ácido. O tempo de equilíbrio para a fotodegradação do sulfametoxazol utilizando a placa de Zn recoberta com ZnO foi de 120 minutos com remoções de 95%, sob radiação artificial, seguindo uma lei de velocidade de pseudo-primeira ordem. A determinação de DQO e da concentração de nitrato indicaram que houve uma pequena mineralização do poluente, apesar da elevada remoção, mostrando que provavelmente houve a formação de espécies intermediárias. Além disso, a placa de zinco recoberta com ZnO apresentou uma eficiência catalítica praticamente inalterada em até 10 repetições de fotodegradação. No entanto, ao final do processo a concentração de zinco na amostra degradada estava acima da permitida pelos órgãos ambientais, sendo necessário a utilização de um pós-tratamento para a remoção do zinco ou a utilização de solução de sulfametoxazol com pH mais próximo da neutralidade para evitar a dissolução do metal do catalisador.

La pollution atmosphérique urbaine pose des problèmes au niveau de l'environnement et de la santé publique pour plus de la moitié de la population mondiale. Afin de réduire la pollution de fond dans les villes, un matériau cimentaire innovant a été développé et permet de dégrader les polluants atmosphériques grâce à ses propriétés photocatalytiques induites par l'ajout de TiO2. Ce travail a porté sur la corrélation entre les propriétés physico-chimiques et l'efficacité photocatalytique d'un mortier enrichi en TiO2 lors de la dégradation de 2 composés organiques volatils (COV), le formaldéhyde et le toluène ainsi que sur un mélange d'oxydes d'azote (NOx). Le taux de présence de la surface en dioxyde de titane, le pourcentage relatif de titane et l'absorbance des photons UV par TiO2 ont été respectivement déterminés par spectroscopie Raman, microscopie électronique à balayage couplé à une analyse X et spectroscopie UV-visible par réflexion diffuse. La proportionnalité entre ces 3 grandeurs a été démontrée. L'efficacité photocatalytique des matériaux cimentaires enrichis en TiO2 a été mise en évidence pour la dégradation des 2 COV et des NOx. L'efficacité photocatalytique est reliée à la présence de TiO2 en surface ainsi qu'à la capacité de TiO2 à absorber des photons UV. La matrice cimentaire permet également, à l'obscurité, de réduire significativement la concentration en formaldéhyde. L'étude de l'influence des paramètres matériaux et environnementaux a montré l'importance de la teneur en TiO2, du flux lumineux et de l'humidité relative sur les propriétés photocatalytiques du mortier et permis de contribuer à une meilleure compréhension des réactions intervenant lors de la dégradation des polluants par un matériau cimentaire photocatalytique / More than half of the world population is exposed to urban air pollution which poses problems for the environment and human health. To reduce the background of the pollution in cities, an innovative cementitious material has been developed and used to degrade pollutants thanks to its photocatalytic properties induced by the addition of TiO2. This work was focused on the correlation between physicochemical properties and the photocatalytic efficiency of a mortar enriched with TiO2 during the degradation of two volatile organic compounds (VOCs), formaldehyde and toluene as well as a mixture of nitrogen oxides (NOx). The occurence rate of of titanium dioxide on the surface, the relative percentage of titanium and the absorptance of UV photons by TiO2, respectively, were determined by Raman spectroscopy, scanning electron microscopy coupled with X-ray analysis and UV-visible diffuse refectance spectroscopy. Proportionality between these three variables has been demonstrated. The photocatalytic efficiency of TiO2-rich cementitious materials has been demonstrated for the degradation of the 2 VOCs and also for NOx. The photocatalytic efficiency is related to the presence of TiO2 on the surface and the ability of TiO2 to absorb UV photons. The cement matrix can also, in the dark, reduced significantly the concentration of formaldehyde. The study of the influence of materials and environmental parameters showed the importance of the TiO2 content, the luminous flux and relative humidity on the photocatalytic properties of the mortar and allowed to contribute to a better understanding of the reactions occurring during the degradation of pollutants by a photocatalytic cementitious material

Des catalyseurs à base de métaux nobles (Pt, Pd, Ir, Ru et Rh) supportés (TiO2, ZrO2, CeO2 et CeZrO2) ont dans un premier temps été préparés. L'Oxydation en Voie Humide Catalytique de l'ammoniaque en présence de ces catalyseurs a alors été réalisée. Le platine est le métal le plus actif. L'iridium et le palladium sont les plus sélectifs en diazote. Le catalyseur Pt/TiO2 est le plus performant car il combine une très forte activité et une sélectivité en diazote peu éloignée de celles de l'iridium et du palladium. Une étude approfondie sur ce catalyseur (méthode de préparation, nature du précurseur métallique,…) a montré que seule la basicité de surface du catalyseur a un impact négatif sur la sélectivité en diazote. Les autres paramètres étudiés sont non significatifs. Le travail réalisé sur les conditions opératoires (PO2, T, mcatalyseur, pH et concentration d'ammoniaque) toujours en présence de Pt/TiO2 ont montré qu'il est nécessaire de contrôler la fonction oxydante et notamment le rapport nO2/nNH3. En effet, si la valeur de ce rapport est trop élevée (nO2/nNH3 >> 0,75) alors la sélectivité en diazote se dégrade fortement. Pour terminer, des catalyseurs bimétalliques PtIr/TiO2 et PtPd/TiO2 ont été préparés afin d'allier l'activité du platine à la sélectivité en diazote du palladium ou iridium. L'utilisation de ces catalyseurs s'avère peu intéressante car leur comportement est similaire à celui des mélanges mécaniques. De plus, la sélectivité en diazote est également dégradée pour nO2/nNH3 >> 0,75 avec ces catalyseurs / TiO2, ZrO2, CeO2 and CeZrO2 supported noble metal catalysts (Pt, Pd, Ir, Ru and Rh) have been in a first time prepared to be used in the Catalytic Wet Air Oxidation of ammonia. The first results show that platinum is the most active metal. Palladium and iridium are the most selective toward nitrogen. Pt/TiO2 is the most interesting catalyst because it combines a very strong activity and a selectivity toward nitrogen close to iridium and palladium. An in-depth study on this catalyst (preparation method, nature of the metallic precursor…) shows that the single parameter which has a negative impact on the selectivity toward nitrogen is the basicity of the catalyst surface. The work realized on the operating conditions (PO2, catalyst weight, pH and ammonia concentration) in the presence of Pt/TiO2 shows the necessity to control the oxidizing function and particularly the nO2/nNH3 ratio. Indeed, if the value of this ratio is too high (nO2/nNH3 >> 0,75) then the selectivity toward nitrogen degrades strongly. To end, PtIr/TiO2 and PtPd/TiO2 bimetallic catalysts have been prepared to combine the activity of the platinum and the selectivity of palladium/iridium to nitrogen. These catalysts are not interesting because their behaviour is similar to the mechanical mixtures. Furthermore, the selectivity toward nitrogen is also degraded for nO2/nNH3 >> 0,75 with these catalysts

Over the past few decades, inorganic nanostructured materials have elicited a lot of interest due to their high surface-to-volume ratio and many size dependent properties which stem from their nanoscale dimensions. Owing to these distinct properties, they have found applications in widespread fields like catalysis, energy storage, electronics, and biotechnology. In the field of biotechnology, nanotubes and mesoporous materials are attractive vehicles for drug delivery because of their hollow and porous structures and facile surface functionalization. Their inner void can take up large amounts of drug as well as act as gates for the controlled release of drug. These hollow structures can also be used for confining biomolecules like proteins and peptides. The study on protein conformation in biocompatible materials is very important in materials sciences for the development of new and efficient biomaterials(sensors, drug delivery systems or planted devices). Titania(TiO2)has been widely explored for applications in photovoltaic cells, batteries, desalination, sensing, and photocatalysis, to name only a few. The work presented in this thesis focuses on titania based nanostructures for drug delivery and protein confinement. First part of the work focusses on synthesis and characterization of Fe-doped TiO2 nanotubes. Fe-doped TiO2 nanotubes were demonstrated as controlled drug delivery agents. In vitro cytotoxic effects of Fe-doped titania nanotubes were assessed by MTT assay by exposing Hela cell line to the nanotubes. Second part of the work focusses on synthesis and characterization of TiO2 nanotubes by two synthesis procedures, namely hydrothermal and sol-gel template synthesis. Myoglobin, a model globin protein was encapsulated in hydrothermally synthesized TiO 2 nanotubes(diameter 5 nm) and sol-gel template synthesized TiO2 nanotubes(diameter 200 nm). Effect of encapsulating myoglobin these nanotubes was studied. The electrochemical activity and structure of myoglobin were studied by cyclic voltammetry and circular dichroism respectively. Direct electron transfer was found to be enhanced upon confinement in 200 nm diameter nanotubes. No such enhancement was observed upon encapsulation in hydrothermally synthesized nanotubes. In addition to this, the thermal stability of myoglobin was found to be enhanced upon confinement inside 200 nm diameter TiO 2 nanotubes.

The present thesis is focused on the synthesis and environmental applications of polyaniline and its nanocomposites. It is organized in six chapters and brief discussions of the contents of the individual chapters are given below. Chapter 1 reviews two important water purification methods: adsorption and photocatalysis, which are widely discussed in literature. A general introduction to conducting polymers has been given and their photocatalytic activity has been described. Chapter 2 reports the application of polyaniline emeraldine salt for the removal of anionic dyes from aqueous solutions by adsorption. A possible mechanism for the anionic dye adsorption by PANI emeraldine salt has been proposed. The electrostatic interaction between the positively charged PANI backbone and dye anions is responsible for significant dye adsorption. The kinetic parameters for the adsorption of anionic dyes on PANI have also been determined. In Chapter 3, we investigate the adsorption and desorption of anionic dyes from aqueous solution by PANI doped with different protonic acids. PANI with three dopants, namely p-toluene sulfonic acid (PTSA), camphor sulfonic acid (CSA) and dodecyl benzene sulfonic acid (DBSA) were used to adsorb various dyes. The adsorbed dyes were desorbed from the polymer by using a basic aqueous solution. It was found that the adsorption of dye is dependent on the size and nature of the dopant acids. The influence of different dopants on the adsorption and desorption kinetic parameters was also examined. In chapter 4, the inherent property of PANI to adsorb dyes has been explored for the detection of dyes by electrochemical method. The changes in the CV of PANI film coated on Pt electrodes on addition of dye have been employed for detection of dye in aqueous solution. Furthermore, PANI coated stainless steel (SS) electrodes show a change in current intensity of Fe2+/Fe3+ redox peaks due to addition of dye in the electrolyte solution. Chapter 5 describes the synthesis and characterization of polyaniline-grafted-chitosan (CPANI) with different grafting ratios. The mechanical properties and the crystallinity of CPANI were investigated by means of nanoindentation and X-ray diffraction experiments, respectively. CPANI has been further self-assembled into multilayer thin film via versatile and simple layer-by-layer (LbL) approach. Negatively charged hyaluronic acid (HUA) was used as complementary polyelectrolyte for the self-assembly. LbL growth of the multilayer thin films has been monitored with UV-vis spectral analysis as well as by AFM. The formation of thin film has been further characterized by SEM. The pH responsive behavior of CPANI/HUA multilayer thin film has been investigated. Reusability of this thin film has been investigated by repeating the pH responsive experiments for 10 cycles. Chapter 6 is focused on the preparation of nanocomposite thin films of CPANI/PSS/TiO2 via LbL approach. LbL growth of this self-assembly was monitored by UV-vis spectral analysis and porous nature was observed from SEM images. Poly (styrene sulfonate) (PSS) was used as bridging layer between TiO2 nanoparticles and CPANI for the multilayer self-assembly. Incorporation of CPANI within this LbL self-assembly enhanced the dye degradation ability of the thin film by increasing the availability of dye molecules around the TiO2 nanoparticles. Furthermore, CPANI may act as a sensitizer to enhance the photocatalytic activity of TiO2. The effects of surface area of the multilayer thin film and amount of catalysts (TiO2 nanoparticles) incorporated in the self-assembly were described based on the kinetics of the dye degradation reactions. The same multilayer thin film can be efficiently used for dye degradation several times. The work presented in this thesis utilizes unique dye adsorption properties of PANI and its copolymers. The change in conductivity of PANI after dye adsorption and the electrochemical dye detection in aqueous medium promise the potential of PANI as a dye sensing material in waste water at very low concentration. The nanocomposites of CPANI/PSS/TiO2 present a novel material for photocatalysis.

Les effluents industriels sont constitués de molécules de natures très diverses, plus ou moins réfractaires aux classiques traitements biologiques. Les normes de rejets évoluant régulièrement vers des contraintes de plus en plus sévères, il semble aujourd'hui nécessaire de proposer des solutions complémentaires pour atteindre de hauts rendements d'épuration. Le premier procédé mis en oeuvre dans ce travail est l'adsorption sur charbon actif. Le caractère novateur de cette technique se situe dans l'utilisation de charbons actifs fabriqués à partir de boues de stations d'épuration d'eaux usées. La seconde méthode est un procédé hybride innovant combinant adsorption et photocatalyse avec TiO2. Les eaux industrielles ciblées sont les effluents colorés, représentés par la tartrazine, et les effluents phénolés représentés par le phénol, l'acide p-hydroxybenzoïque, le p-chlorophénol er le p-nitrophénol. Pour traiter par adsorption les eaux chargées en phénols, plusieurs charbons actifs commerciaux et six charbons de boues ont été utilisés. Il ressort de cette première étude que, malgré leurs faibles surfaces spécifiques, certains charbons de boues présentent des performances très satisfaisantes. Le procédé séquentiel combinant adsorption et photocatalyse a été réalisé avec plusieurs matériaux: un tissu Ahlstrom contenant du charbon et du TiO2, un charbon actif avec dépôt de TiO2 par MOCVD puis un mélange de charbon actif et TiO2 en poudre. Des résultats prometteurs ont été obtenus pour dégrader la tartrazine, en particulier avec le TiO2 déposé sur charbon actif montrant que la proximité de sites d'adsorption et photocatalytique améliore les performances de l'oxydation / In order to explore a new sequential process for water treatment its two steps, adsorption on activated carbon and in situ photocatalytic oxidative regeneration, were investigated successively. Several commercial activated carbons (AC) and sewage sludge based activated carbons (SBAC) were tested with several phenols and one dye as pollutants. Despite low BET surface SBAC exhibits convenient adsorption properties. Photocatalysis on TiO2 was carried out with several materials to achieve activated carbon adsorption- egeneration process: a multilayer tissue with fixed granular AC and TiO2 on a sheet, a composite with TiO2, CVD deposited on AC, and AC-TiO2 powder mixture for comparison. Promising results were obtained especially with TiO2 deposited on AC proving the vicinity of adsorption and photocatalytic sites to be beneficial

<p>Ispitana je direktna i indirektna razgradnja odabranih&nbsp; &beta;-blokatora (metoprolol- tartarata, MET i propranolol-hidrohlorida, PRO) kao i diuretika (hidrohlortiazida, HCTZ) i njegovog stabilnog intermedijera hidrolize 4-amino-6-hlor-1,3-benzendisulfonamida (ABSA). Praćena je i kinetika razgradnje direktnom i indirektnom fotolizom uz primenu UVA, UVC, sunčevog i simuliranog sunčevog zračenja (SSZ). Najpre je ispitana&nbsp; stabilnost MET pod dejstvom SSZ, UVA, UVC, UVA/H₂O_{2 ,} i UVA/&nbsp; BrO₃^-. Dalje je ispitana efikasnost razgradnje MET pod dejstvom O₃i UVC/O_3. Identifikovano je deset intermedijera tokom UVC, O_3&nbsp;i UVC/O₃ razgradnje, pri&nbsp; čemu samo jedan ima značajno vi&scaron;u toksičnost prema algama i bakterijama u odnosu na ostale. Efikasnost fotokatalitičke razgradnje MET je ispitana u TiO₂ suspenzijama sa komercijalnim katalizatorima (Wackherr i Degussa P25). Mehanizam fotokatalitičke razgradnje je detaljno ispitan, pri&nbsp; čemu je identifikovano&nbsp; četrnaest intermedijera. EC₅₀ vrednost MET i njegovih sme&scaron;a nastalih pri fotokatalitičkoj razgradnji su određene na tri ćelijske linije sisara (H-4-II-E, HT-29 i MRC-5). Kako bi se povećala efikasnost&nbsp; rocesa fotokatalitičke razgradnje primenom komercijalnih katalizatora, ispitan je&nbsp; uticaj prisustva elektron-akceptora u suspenziji, pri čemu je upoređen uticaj O₂/H₂O₂, i O₂/ BrO₃^-&nbsp;na mehanizam razgradnje. Na osnovu teorije funkcionala gustine stekao se uvid u promene unutar molekula MET u prisustvu reaktivnih radikala. Takođe, ispitana je efikasnost nedopiranih TiO₂ , kao i dopiranih La(III) nanoprahova sintetisanih sol&minus;gel postupkom, u razgradnji MET. Uticaj temperature &nbsp;kalcinacije na fotokatalitičku efikasnost TiO 2 nanoprahova dopiranih pomoću La(III) &nbsp;ispitana je na supstratima MET i PRO, pri čemu je analiziran i uticaj strukture&nbsp; polaznog jedinjenja na&nbsp; informacija efikasnost fotokatalitičke razgradnje. Rezultati su upoređeni sa nedopiranim TiO₂nanoprahom i TiO₂Degussa P25 (pri pH-vrednosti 9). Pored toga, ispitana je kinetika i toksičnost PRO i njegovih intermedijera nastalih tokom razgradnje sa TiO₂Degussa P25. Ispitan je i uticaj strukture polaznog jedinjenja (MET, HCTZ i ABSA) na fotorazgradnju pod dejstvom&nbsp;UVA, sunčevog i simuliranog sunčevog zračenja, u odsustvu/prisustvu TiO₂ Degussa P25. Takođe, ispitan je i sinergistički efekat MET i ABSA na proces hidrolize, direktne fotolize i fotokatalize sa SSZ/TiO₂Degussa P25. Kako bi se stekao uvid u toksičnost proučavanih sistema, ispitan je njihov uticaj na rast odabranih ćelijskih linija sisara.</p> / <p>Direct and indirect degradation of selected&nbsp; &beta;-blockers (metoprolol tartrate, MET and&nbsp;propranolol hydrochloride, PRO) and also diuretic (hydrochlorothiazide, HCTZ) in &nbsp;addition to its stable hydrolysis intermediate 4-amino-6-chloro-&nbsp;&nbsp; 1,3-benzenedisulfonamide (ABSA) were investigated. The kinetics of their degradation obtained by direct and indirect photolysis under UVA, UVC, sunlight and simulated sunlight irradiation (SSI) have been followed. Firstly, the stability of MET under influence of SSI, UVA, UVC, UVA/H₂O₂ , and UVA/&nbsp; BrO₃^- has been investigated. Further, the efficiency of MET degradation under influence of O₃, and UVC/O₃ has been explored. Ten intermediates have been identified during the UVC, O₃, and UVC/O₃ treatments, while only one intermediate had significantly higher toxicity towards the algae and bacteria in respect to the others. Efficiency of&nbsp; photocatalytic degradation of MET was investigated in TiO₂ suspensions with&nbsp;commercial catalysts (Wackherr and Degussa P25). Mechanism of photocatalytic degradation was investigated in detail according to which fourteen intermediates were identified. EC 50 &nbsp;value of MET and its mixtures formed during the photocatalytic degradation has been determined at three mammalian cell lines (H-4-II-E, HT-29, and MRC-5). In order to improve the efficiency of photocatalytic degradation process applying commercial catalysts, the influence of presence of electron acceptors in suspension has been investigated and the influence of O₂/H₂O_2&nbsp;and O₂/BrO₃^- to the mechanism of degradation has been compared. Based on the density&nbsp; functional theory an insight to the changes within MET molecule in the presence of reactive radicals has been made. Also, the efficiency of bare TiO₂, as well as&nbsp;doped La(III) nanopowders synthesized by sol-gel procedure, in the degradation of&nbsp; MET has been investigated. The influence of calcination temperature on&nbsp; hotocatalytic efficiency of TiO_2&nbsp;nanopowders doped with La(III) has been studied on the MET and&nbsp; PRO substrates, and the influence of structure of the starting compound on the&nbsp; efficiency of &nbsp;photocatalytic degradation had been analyzed. Results have been&nbsp; compared with bare TiO_2&nbsp;nanopowder and TiO₂ Degussa P25 (at pH value of 9). Besides, kinetics and toxicity of PRO and its intermediates formed during the degradation with TiO₂ Degussa P25 have been investigated. The influences of starting compound&rsquo;s structure (MET, HCTZ, and ABSA) to photodegradation under UVA, sunlight and SSI, in the absence/presence of TiO₂ Degussa P25, have been investigated. Also, the synergistic effects of MET and ABSA to the process of&nbsp; hydrolysis, direct photolysis, and photocatalysis with SSI/TiO₂ Degussa P25 have been investigated. In order to get &nbsp;an insight into the toxicity of the studied systems, their influence on the growth of selected mammalian cell lines has been investigated as well.</p>

M.Tech. (Department of Chemistry, Faculty of Applied and Computer Sciences), Vaal University of Technology. / To replace the conventional wastewater treatment technology, photocatalysis has the best potential due to its utilization of visible light to photodegrade organic and inorganic contaminants. However, agglomeration of nanoparticles leads to serious decrease in photocatalytic performance when applied in slurry form, due to hindrance effect. TiO2 semiconductor photocatalyst mediated advanced oxidation process is referred to as one of the most efficient technologies to degrade organic pollutants in water. However, TiO2 semiconductor for water purification hinders large scale applicability due to poor activity under visible light and the recombination of photogenerated electron and hole pairs. The modification of TiO2 semiconductor photocatalyst with carbon dots (CDs) is of high importance due to low toxicity, aqueous stability, enhanced surface area, economic feasibility, good biocompatibility and chemical inertness of CDs. Herein, strategies are highlighted to improve the activity of TiO2 semiconductor photocatalyst by coupling it with CDs and Fe2O3. In this study, we study the morphological influence of TiO2 nanostructures on photocatalytic degradation of tetracycline hydrochloride present in industrial wastewater. TiO2 nanostructures, nanotubes, nanospheres and nanofibers were Synthesized using the hydrothermal technique. TiO2 nanotubes, nanofibers and nanospheres were prepared by the hydrothermal treatment of TiO2 nanoparticles with different NaOH concentrations (5, 10 and 12 N) at 120 and 140 ˚C; afterwards, HCl was added until it reached pH 2. Both the crystalline phase and coordination of the TiO2 nanotubes, nanofibers and nanospheres were composed principally. Likewise, the surface area, pore volume and pore size of the TiO2 nanotubes, nanofibers and nanospheres changed with the NaOH rinsing treatment. The photocatalytic activity for tetracycline degradation were strongly enhanced by the nanofibers and nanotubes in the basic and acid media, respectively, showing a relationship between their structure and the medium. TiO2 nanostructures and the composite material were characterized by scanning electron microscope\SEM), X-Ray Diffraction (XRD), transmission electron microscope (TEM) and Fourier transform infrared (FTIR). BET surface area analysis was carried out using nitrogen adsorption desorption curves. The results show that TiO2 morphology had great influence on photocatalytic degradation of tetracycline hydrochloride due to difference in specific surface area and pore volume of nanostructures. The photocatalytic degradation experiments were carried out for three hours under visible-LED light. TiO2 nanofibers show better degradation performance than nanotubes and nanospheres due to presence of large surface area for reaction, higher porosity with dispersion of active sites at different length scales of pores and presence of oxygen vacancies. Agricultural biomass pine bark serves as a carbon source and was doped into TiO2-nanofibers (TNF) to fabricate the composite material (CD-TNF). CD-TNF composite nanofibers were prepared via a facile hydrothermal method. This study revealed that the photocatalytic efficiency of tetracycline (TC) under visible light irradiation of the composite nanofiber is higher than that of pure TiO2-nanofiber. The anchored CDs can both enhance the light absorption and suppress photogenerated electron hole recombination which results in the enhancement of catalytic and antibacterial properties. The CDs can better capture and transfer photogenerated electrons through the Ti-O-C and Fe-O-C bonds. Moreover, CDs can improve the utilization of photogenerated electrons and the electrons in CDs are captured by O2 to produce O2•- radicals and the role of O2•- radicals in the photocatalytic process is significantly improved. A new efficient photocatalyst consisting of TiO2/CD/Fe2O3 composite material was Synthesized by the hydrothermal treatment and applied in the photodegradation of 5 mg/L tetracycline hydrochloride (TC) under visible-LED light. The CDs/TiO2/Fe2O3 composite showed enhanced photocatalytic performance for tetracycline photodegradation when compared with TiO2/CDs and pure TiO2 under the visible light irradiation. The mechanism of the improved photocatalytic activity over CDs/TiO2/Fe2O3 was also investigated. The influence of the interface formation between Fe2O3 and TiO2/CDs affects severely the charges separation efficiency and enhances the electron transfer to keep on the existence of Fe3+/Fe2+ moieties that take significant role in the reaction mechanism.

La photocatalyse est une voie de synthèse prometteuse de l’hydrogène comme carburant solaire. La production photocatalytique est un moyen, à la fois de stocker l’énergie solaire sous forme d’énergie chimique et de produire des carburants de manière renouvelables en utilisant l’eau ou des alcools biosourcés comme matière première. L’objectif de cette thèse est d’étudier la déshydrogénation photocatalytique d’alcools à l’aide de sulfures de métaux de transitions, supportés sur TiO2 (MSx/TiO2). Ces sulfures de métaux de transitions ont des propriétés d’activation de l’hydrogène, des propriétés électrochimiques et des propriétés optiques intéressantes. Une série de sept MSx/TiO2 (M = Co, Ni, Cu, Mo, Ru, Ag, Hg) ont été étudiés. La réaction de déshydrogénation photocatalytique du propan-2-ol est utilisée comme réaction modèle. Des corrélations sont établies entre les propriétés intrinsèques de ces MSx/TiO2 et leur activité photocatalytique. De plus, la mesure d’énergie d’activation d’apparente apporte une compréhension supplémentaire sur les mécanismes photocatalytiques. Cette dernière montre que la production photocatalytique d’hydrogène est principalement limitée par les phénomènes de séparation et de transfert de charges dans les photocatalyseurs. Ainsi, une méthodologie combinant la spectroscopie de photoélectrons UV et la spectroscopie d’absorption UV-Visbile a été mis en place pour déterminer la structure électronique des poudre photocatalytiques. Ce travail conclue sur le caractère central de la structure électronique en photocatalyse. Dans le cas du photocatalyseur RuS2/TiO2, le transfert électronique est l’étape cinétiquement déterminante pour la déshydrogénation photocatalytique du propan-2-ol / Photocatalysis is a promising way to synthesize H2 as a solar fuel. On one hand, the photocatalytic H2 production stores solar energy under chemical energy. On the other hand, it produces H2 with a renewable process using water and bio-based alcohols as a feedstock. This Ph.D thesis aims to study the photocatalytic dehydrogenation of alcohols with transition metal sulfides supported on TiO2 (MSx/TiO2). Those transition metal sulfides have versatile and highly tunable properties. They can activate H2, they have promising electrochemical behavior and optical properties. Seven MSx/TiO2 (M = Co, Ni, Cu, Mo, Ru, Ag, Hg) are therefore studied. The photocatalytic dehydrogenation of propan-2-ol is used as a model reaction. Structure-activity relationships are found between the intrinsic properties of the MSx/TiO2 and their photocatalytic activity. Measuring an apparent activation energy provides additional mechanistic insights. It shows that the photocatalytic production of hydrogen is mostly limited by the charge carrier separation and by the electronic transfer. Therefore a method combining the UPS and the UV-Visbile absorption spectroscopies has been develop to establish the electronic structure of photocatalytic powders. This work concludes that the electronic structure plays a crucial role in photocatalysis. With RuS2/TiO2 photocatalyst, the electron transfer is evidenced as the rate-determining step of the photocatalytic dehydrogenation of propan-2-ol

The photocatalytic approach is known to be one of the most promising advanced oxidation processes for the tertiary treatment of polluted water. In this paper, β-NaYF4/TiO2 composite films have been synthetized through a novel sol–gel/spin-coating approach using a mixture of β-diketonate complexes of Na and Y, and Yb3+, Tm3+, Gd3+, Eu3+ as doping ions, together with the TiO2 P25 nanoparticles. The herein pioneering approach represents an easy, straightforward and industrially appealing method for the fabrication of doped β-NaYF4/TiO2 composites. The effect of the doped β-NaYF4 phase on the photocatalytic activity of TiO2 for the degradation of methylene blue (MB) has been deeply investigated. In particular, the upconverting TiO2/β-NaYF4: 20%Yb, 2% Gd, x% Tm (x = 0.5 and 1%) and the downshifting TiO2/β-NaYF4: 10% Eu composite films have been tested on MB degradation both under UV and visible light irradiation. An improvement up to 42.4% in the degradation of MB has been observed for the TiO2/β-NaYF4: 10% Eu system after 240 min of UV irradiation.