Dans ce travail de thèse, les radicaux hydroxyles et sulfates, générés par les procédés électro-Fenton et électro-persulfate utilisant une anode en fer, respectivement, ont été utilisés pour la dégradation des édulcorants synthétiques et un colorant azoïque. Les études réalisées sont essentiellement concentrées sur : efficacité de dégradation, mécanismes d'oxydation, schémas de minéralisation et évolution de la toxicité lors de traitement des polluants cibles.1. Le procédé électro-Fenton a montré une grande efficacité dans la dégradation oxydative de l'Aspartame (ASP). La dégradation et la minéralisation sont essentiellement affectées par la concentration du catalyseur (Fe2+) et l'intensité du courant. La constante de vitesse absolue de la réaction d'hydroxylation de l'ASP a été déterminée comme (5,23±0,02) x 109 M-1 s-1. Les acides oxalique, oxamique et maléique ont été identifiés comme sous-produits aliphatiques. La toxicité de la solution (méthode Microtox) augment dans un premier temps et ensuite diminue progressivement lors du traitement.(2) L'édulcorant artificiel Saccarine (SAC) a été efficacement dégradée par procédé électro-Fenton avec anodes DSA, Pt et BDD. Cependant, l'utilisation de l'anode BDD a accéléré significativement la minéralisation de la SAC. Les conditions optimales pour la minéralisation efficace de la SAC étaient: [SAC]: 0,2 mM, [Fe2+] (catalyseur): 0,2 mM, [Na2SO4] (électrolyte): 0,05 M, I (courant): 200 mA et pH: 3. Les acides oxalique, formique et maléique ont été identifiés comme sous-produits aliphatiques. La mesure de la toxicité indique une augmentation en début d'électrolyse (formation des intermédiaires toxiques) et puis une diminution progressive le long du traitement.(3) L'édulcorant artificiel Sucralose (SUC) a été complètement minéralisée en 360 min de traitement par procédé électro-Fenton avec l'anode Pt ou BDD. Le taux de minéralisation est affecté par la concentration de Fe2+ et le courant appliqué. L'efficacité du courant de minéralisation diminue avec l'augmentation du courant de 100 à 500 mA avec les deux anodes. Les acides oxalique, pyruvique, formique et glycolique ont été détectés au cours du processus de minéralisation.(4) Les solutions du colorant azoïque Orange II ont été effectivement décolorées par les radicaux sulfates générés par l'activation électrochimique du peroxydisulfate (PDS) utilisant un catalyseur solide, FeOOH (procédé CE/α-FeOOH/PDS). Le pH initial a peu d'effet sur la décoloration. La méthodologie RSM (Response Surface Methodology) basée sur le modèle Box-Behnken a été appliquée pour analyser les variables expérimentales. Les résultats indiquent que le courant a un effet positif sur la vitesse de décoloration. L'interaction du dosage de l'α-FeOOH et la concentration de PDS ont des effets significatifs. Les résultats d'analyse de variance (ANOVA) ont confirmé que les modèles proposés étaient exactes et fiables pour l'analyse des variables du procédé CE/α-FeOOH/PDS. Le catalyseur solide α-FeOOH a montré une bonne stabilité structurelle et pourrait être réutilisé.(5) Les solutions d'Orange II ont été dégradés par les radicaux sulfates obtenus par le même procédé mais avec catalyseur Fe3O4 : EC/Fe3O4/PDS. La vitesse de décoloration est affecté principalement par : pH initial de la solution, densité du courant, concentration de PDS et dosage de Fe3O4. La solution a été totalement décolorée en 60 min dans les conditions suivantes: [Orange II]0: 25 mg/L, [PDS]: 10 mM, [Fe3O4]: 0,8 g/L, densité du courant (j): 8,4 mA/cm2 et pH initial: 6,0. Les expériences de recyclage ont montré que les particules de Fe3O4 étaient stables et pourraient être réutilisées. Les spectres XPS ont montré la formation de Fe(II) sur la surface des particules de Fe3O4 lors de traitement. Les principaux intermédiaires ont été séparés et identifiés par la technique GC-MS et un schéma plausible de dégradation d'Orange II a été proposé / In this paper, electro-Fenton and sulfate radical-based electro-Fenton-like processes were used to degrade artificial sweeteners and azo dye. The results obtained during the research concern the removal efficiency, the oxidation mechanism, degradation pathway and toxicity evolution of target pollutants.(1) Electro-Fenton process was a effective method for the degradation of ASP in water. The removal and mineralization rate was affected by the Fe2+ concentration and applied current. The absolute rate constant of hydroxylation reaction of ASP was (5.23 ± 0.02) × 109 M–1 S–1. Short-chain aliphatic acids such as oxalic, oxamic and maleic acid were identified as aliphatic intermediates in the electro-Fenton process. The bacteria luminescence inhibition showed the toxicity of ASP solution decreased after it reached a maximum during the first period of the oxidation reaction.(2) Artificial sweetener SAC could be degraded effectively by electro-Fenton process with a DSA, Pt or BDD anode. However, the using of BDD anode could accelerate the mineralization of SAC. The optimal conditions for SAC removal were SAC concentration 0.2 mM, Fe2+ concentration 0.2 mM, Na2SO4 concentration 50 mM, applied current 200 mA and initial pH 3.0. Oxalic, formic, and maleic acid were observed as aliphatic byproducts of SAC during electro-Fenton process. The bacteria luminescence inhibition showed the toxicity of SAC solution increased at the beginning of electrolysis, and then it declined until the end of the reaction.(3) Artificial sweetener Sucralose could be completely mineralized in a 360 min reaction by electro-Fenton process with a Pt or BDD anode. The mineralization rate was affected by the Fe2+ concentration and applied current. The mineralization current efficiency (MCE) decreased with rising applied current from 100 to 500 mA with both Pt and BDD anode. Oxalic, pyruvic, formic and glycolic acids were detected during the oxidation of sucralose.(4) Orange II was effectively decolorized by EC/α-FeOOH/PDS process. The initial pH of Orange II solution had little effect on the decolorization of Orange II. RSM based on Box-Behnken statistical experiment design was applied to analyze the experimental variables. The response surface methodology models were derived based on the results of the pseudo-first-order decolorization rate constant and the response surface plots were developed accordingly. The results indicated the applied current showed a positive effect on the decolorization rate constant of Orange II. The interaction of α-FeOOH dosage and PDS concentration was significant. The ANOVA results confirmed that the proposed models were accurate and reiable for the analysis of the varibles of EC/α-FeOOH/PDS process. The catalystα-FeOOH showed good structural stability and could be reused.(5) Aqueous solutions of Orange II have been degraded effectively in the EC/Fe3O4/PDS process. The decolorization rate was affected by the initial pH of Orange II solution, current density, PDS concentration and Fe3O4 dosage. Orange II can be totally decolorizated in a 60 min reaction when initial Orange II concentration was 25 mg/L, PDS concentration was 10 mM, Fe3O4 dosage was 0.8 g/L, current density was 8.4 mA/cm2 and initial pH was 6.0. Recycle experiments showed Fe3O4 particles were stable and can be reused. XPS spectrum indicated Fe(II) was generated on the surface of Fe3O4 particles after reaction. The main intermediates were separated and identified by GC-MS technique and a plausible degradation pathway of Orange II was proposed

Orientador: Raquel Fernandes Pupo Nogueira / Resumo: Para remover produtos farmacêuticos em água residual, estudou-se o compósito óxido de grafeno/magnetita (OG/Fe3O4) como catalisador no processo Fenton heterogêneo. A caracterização do material sintetizado a partir da co-precipitação de magnetita na presença de óxido de grafeno revelou que as folhas de óxido de grafeno foram cobertas com nanopartículas cubicas de magnetita, com um tamanho médio de 7 nm. Verificou-se pelo espectro FTIR que o compósito é formado pela ligação Fe-O-C do grupo carboxílico do óxido de grafeno. O nanocompósito mostrou superparamagnetismo à temperatura ambiente que diminui com o aumento da quantidade de óxido de grafeno, o que facilitou sua coleta para testes de reutilização. Verificou-se pelos espectros de Raman que o grafite precursor foi oxidado, enquanto o difratograma de raios X mostrou um aumento na distância interplanar devido à esfoliação do precursor. Devido à associação de efeitos entre adsorção e degradação, foi possível remover pelo menos 98% da cafeína em água (< limite de detecção) após uma hora. O nanocompósito mostrou uma atividade catalítica superior em comparação à magnetita isolada, com um efeito sinérgico de até 17,4 no escuro devido a um melhor transporte para a superfície do catalisador, que resultou em maior geração de radicais HO.. A constante de velocidade superficial aumentou em até 3 ordens de grandeza com a presença de óxido de grafeno. O catalisador mostrou dependência do pH do meio, com melhor eficiência de degradação em ... (Resumo completo, clicar acesso eletrônico abaixo) / Abstract: To remove pharmaceutical products in wastewater, graphene oxide/magnetite (GO/Fe3O4) composite was studied as a catalyst in the heterogeneous Fenton process. The characterization of the synthesized material from magnetite co-precipitation in the presence of graphene oxide revealed that the graphene oxide sheets were covered with cubic-like nanoparticles of magnetite, with an average size of 7 nm. It was also found, from the FTIR spectrum, that the Fe-O-C bond of the graphene oxide carboxylic group links the composite. The nanocomposite showed superparamagnetism at room temperature which decreases with increasing amount of graphene oxide, which facilitated its collection for reuse tests. Raman spectra showed that the precursor graphite was oxidized, while the X-ray diffractogram showed an increase in interplanar distance due to precursor exfoliation. Due to the association of effects between adsorption and degradation, it was possible to remove at least 98% of caffeine in water (<detection limit) after one hour. Nanocomposite showed a higher catalytic activity compared to isolated magnetite, with a synergistic effect of up to 17,4 in the dark due to better transport to the catalyst surface, which resulted in higher generation of HO. radicals. The rate constant increased up to three orders of magnitude with the presence of graphene oxide. The catalyst showed medium pH dependence, with better degradation efficiency at pH 3. / Mestre

<p>Cilj&nbsp; ovog&nbsp; rada&nbsp; bio&nbsp; je&nbsp; ispitivanje&nbsp; mogućnosti&nbsp; primene&nbsp; modifikovanog&nbsp; bentonita&nbsp; kao katalizatora&nbsp; (ferioksalat&nbsp; i&nbsp; Al,&nbsp; Fe-bentonit&nbsp; katalizatori)&nbsp; u&nbsp; Fenton&nbsp; i&nbsp; foto-Fenton&nbsp; procesu&nbsp; uklanjanja tekstilne&nbsp; reaktivne&nbsp; boje&nbsp; Reactive&nbsp; Red&nbsp; 120.&nbsp; Do&nbsp; sada&nbsp; su&nbsp; objavljene&nbsp; studije&nbsp; primene&nbsp; heterogenog Fenton procesa sa različitim koncentracijama gvožđau katalizatorima i sa kompleksom ferioksalata,međutim, njihovo poređenje u smislu efikasnosti obezbojavanja nije istraženo, &scaron;to je bio jedan od fokusa&nbsp; istraživanja&nbsp; u&nbsp; ovom&nbsp; radu.&nbsp; Osim&nbsp; toga,&nbsp; potencijal&nbsp; sunčeve&nbsp; energije&nbsp; predstavlja&nbsp; 16,7%&nbsp; od ukupno&nbsp; iskoristivog&nbsp; potencijala&nbsp; obnovljivih&nbsp; izvora&nbsp; energije&nbsp; u&nbsp; Srbiji,&nbsp; dok&nbsp; je&nbsp; prosečno&nbsp; sunčevo zračenje&nbsp; u&nbsp; Srbiji&nbsp; oko&nbsp; 40%&nbsp; vi&scaron;e&nbsp; od&nbsp; evropskog&nbsp; proseka,&nbsp; čineći&nbsp; ga&nbsp; vrlo&nbsp; zanimljivim&nbsp; za&nbsp; primenu&nbsp; u ovom tipu tretmana. U cilju &scaron;to boljeg iskori&scaron;ćenjasunčevog zračenja i unapređenja fotokatalitičkih performansi&nbsp; procesa&nbsp; primenjen&nbsp; je&nbsp; parabolični&nbsp; koncentri&scaron;ući&nbsp; reaktor,&nbsp; koji&nbsp; je&nbsp; za&nbsp; ovu&nbsp; vrstu&nbsp; procesa prvi put upotrebljavan. Proučavano je u kojoj meri je solarna fotokataliza značajan segment tehnike za tretman otpadnih voda tokom degradacije perzistentnih jedinjenja, kao &scaron;to je organska azo boja. Takođe, utvrđen je i potencijal fotolize vodonik-peroksida za obezbojavanjem sintetičkog rastvora date&nbsp; boje.&nbsp; Prva&nbsp; faza&nbsp; imala&nbsp; je&nbsp; za&nbsp; cilj&nbsp; sintezu&nbsp; materijala&nbsp; primenom&nbsp; različitih&nbsp; metoda&nbsp; pripreme&nbsp; i<br />konstrukciju solarnog paraboličnog reaktora, koji će se koristiti u Fenton i foto-Fenton procesima degradacije boje Reactive Red 120. Druga faza je podrazumevala karakterizaciju novosintetisanih materijala i optimizaciju procesa fotokatalize primenom Fenton i foto-Fenton procesa i određivanje postignutih efikasnosti primenjenih procesa. Takođe, vr&scaron;eno je određivanje stepena mineralizacije i identifikacija degradacionih produkata nakon procesa degradacije tekstilne boje Reactive Red 120, kao&nbsp; i&nbsp; primena&nbsp; foto-Fenton&nbsp; procesa&nbsp; na&nbsp; realnom&nbsp; efluentu.&nbsp; Na&nbsp; osnovu&nbsp; dobijenih&nbsp; rezultata&nbsp; tokom primene Fenton procesa i kori&scaron;ćenjem oba tipa katalizatora u periodima niskog i visokog intenziteta zračenja,&nbsp; sa&nbsp; aspekta&nbsp; postizanja&nbsp; visoke&nbsp; efikasnosti&nbsp; obezbojavanja&nbsp; i&nbsp; najmanjeg&nbsp; izluživanja&nbsp; gvožđa,<br />može&nbsp; se&nbsp; zaključiti&nbsp; da&nbsp; je&nbsp; Fenton&nbsp; proces&nbsp; najefikasniji&nbsp; na&nbsp; pH&nbsp; vrednosti&nbsp; 3.&nbsp; AlFeB&nbsp; je&nbsp; pokazao&nbsp; veću reaktivnost čak i pri manje upotrebljenim dozama od0,05 g u odnosu na CuOFeB (0,2 g), kao i mogućnost&nbsp; manje&nbsp; upotrebe&nbsp; vodonik-peroksida&nbsp; od&nbsp; 2,5&nbsp; mM,&nbsp; za&nbsp; postizanje&nbsp; visoke&nbsp; efikasnosti obezbojavanja i postignut visok stepen mineralizacije. Vi&scaron;i intenzitet sunčevog zračenja omogućava odvijanje reakcije obezbojavanja na vi&scaron;im pH vrednostima primenom oba katalizatora tokom fotoFenton&nbsp; procesa.&nbsp; Ovo&nbsp; je&nbsp; posebno&nbsp; izraženo&nbsp; kod&nbsp; CuOFeB&nbsp; tokom&nbsp; letnjeg&nbsp; perioda&nbsp; (pH&nbsp; 7),&nbsp; čak&nbsp; i&nbsp; pri nižim dozama katalizatora. Međutim, najveći udeo u&nbsp; procesu obezbojavanja pri upotrebi CuOFeB katalizatora ima fotoliza vodonik-peroksida (80%). Suprotno ovim rezultatima, pri istim reakcionim uslovima,&nbsp; potrebna&nbsp; je&nbsp; veća&nbsp; količina&nbsp; AlFeB&nbsp; katalizatora&nbsp; (0,1&nbsp; g)&nbsp; i&nbsp; niža&nbsp; pH&nbsp; vrednost&nbsp; reakcije,&nbsp; a efikasnost&nbsp; procesa&nbsp; značajno&nbsp; zavisi&nbsp; od&nbsp; početne&nbsp; koncentracije&nbsp; H₂O₂.&nbsp; Činjenica&nbsp; da&nbsp; se&nbsp; u&nbsp; pripremi katalizatora koristio bentonit kao prirodan, &scaron;irokorasprostranjen i jeftin materijal i solarno zračenje kao obnovljiv i alternativni izvor fotona, gore navedene rezultate bi trebalo uzeti u obzir prilikom analize tro&scaron;kova efikasnosti primenjenog procesa. Takođe, primena unapređenih procesa oksidacije se&nbsp; razmatra&nbsp; kao&nbsp; predlog&nbsp; za&nbsp; najbolju&nbsp; dostupnu&nbsp; tehniku&nbsp; kada&nbsp; je&nbsp; u&nbsp; pitanju&nbsp; tretman&nbsp; otpadne&nbsp; vode tekstilne industrije, dok se kao dodatne nove tehnike uzimaju u obzir foto-oksidacije i ispitivanje mogućnosti&nbsp; njihove&nbsp; primene&nbsp; u&nbsp; preči&scaron;ćavanju&nbsp; otpadne&nbsp; vode&nbsp; u&nbsp; tercijarnom&nbsp; tretmanu&nbsp; na poluindustrijskim sistemima.<br />&nbsp;</p> / <p>The aim of this study was to investigate the decolorization efficiency of Reactive Red 120&nbsp; (RR120) synthetic solution using ferrioxalate (CuOFeB) and Al, Fe-bentonite (AlFeB) catalysts in&nbsp; Fenton&nbsp; and&nbsp; photo-Fenton&nbsp; process.&nbsp; So&nbsp; far,&nbsp; studies&nbsp; of the&nbsp; application&nbsp; of&nbsp; a&nbsp; solar-assisted&nbsp; heterogeneous Fenton process with various Fe loaded catalysts and with ferrioxalate complex have&nbsp; been published, but according to&nbsp;&nbsp; the author&rsquo;s knowledge, their comparison in terms of efficacy of&nbsp; decolorization&nbsp; has&nbsp; not&nbsp; been&nbsp; performed,&nbsp; which&nbsp; was&nbsp; one&nbsp; of&nbsp; the&nbsp; focus&nbsp; of&nbsp; research&nbsp; in&nbsp; this&nbsp; paper.&nbsp; In addition, the potential of solar energy represents&nbsp; 16.7% of the total utilized&nbsp; potential of renewable&nbsp; energy sources in Serbia, while the average solar radiation in&nbsp; Serbia is&nbsp; about 40% higher than the&nbsp; European average, making it very interesting for&nbsp; application in this type of treatment. In order to&nbsp; optimize the use of solar radiation and to improve&nbsp; the photocatalytic performance of the process, parabolic&nbsp; concentrating&nbsp; reactor&nbsp; was&nbsp; used&nbsp; for&nbsp; the&nbsp; first&nbsp; time.&nbsp; As&nbsp; a&nbsp; significant&nbsp; segment&nbsp; of&nbsp; the&nbsp; wastewater&nbsp; treatment&nbsp; technique&nbsp; during&nbsp; the&nbsp; degradation&nbsp; of&nbsp; persistent&nbsp; compounds,&nbsp; such&nbsp; as&nbsp; organic azo dye, solar photocatalysis was studied. Also, the potential of photolysis of hydrogen peroxide for&nbsp; decolorization of the synthetic dye solution was determined. Aim of the first phase of the study was synthesizing&nbsp; materials&nbsp; by&nbsp; using&nbsp; different&nbsp; methods&nbsp; of&nbsp; preparation,&nbsp; and&nbsp; construction&nbsp; of&nbsp; a&nbsp; solar&nbsp; parabolic reactor, which will be used in Fenton andphoto-Fenton dye degradation processes. The second phase involved the characterization of newlysynthesized materials and the optimization of the&nbsp; photocatalytic&nbsp; process&nbsp; by&nbsp; applying&nbsp; Fenton&nbsp; and&nbsp; photo-Fonton&nbsp; processes,&nbsp; as&nbsp; well&nbsp; as&nbsp; the&nbsp; determination&nbsp; of&nbsp; achieved efficiency&nbsp; of&nbsp; the&nbsp; appliedprocesses.&nbsp; Also, the degree&nbsp; of mineralization and the identification of degradation products after applied processes were determined. Application&nbsp; of the photo-Fenton process on a real effluent was conducted as well. Based on the obtained results&nbsp; during&nbsp; Fenton&nbsp; process&nbsp; and&nbsp; using&nbsp; both&nbsp; types&nbsp; of&nbsp; catalysts&nbsp; in&nbsp; periods&nbsp; of&nbsp; low&nbsp; and&nbsp; high&nbsp; intensity&nbsp; of&nbsp; radiation, from the aspect of achieving high efficiency of decolorization and smallest iron leaching,&nbsp; it&nbsp; can&nbsp; be&nbsp; concluded&nbsp; that&nbsp; the&nbsp; Fenton&nbsp; process&nbsp; is&nbsp; most effective&nbsp; at&nbsp; pH&nbsp; 3.&nbsp; AlFeB&nbsp; showed&nbsp; greater&nbsp; reactivity even at less used doses of 0.05&nbsp; g, compared to CuOFeB (0.2 g), and the possibility of using&nbsp; less&nbsp; hydrogen&nbsp; peroxide&nbsp; (2.5&nbsp; mM),&nbsp; achieving&nbsp; high&nbsp; efficiency&nbsp; and&nbsp; a&nbsp; high&nbsp; degree&nbsp; of mineralization. Higher intensity of solar radiationallows the reaction to be carried out at higher pH values when using both catalysts during the photo-Fenton process. This is particularly pronounced largest part in the decolorization process using the CuOFeB catalyst has&nbsp; a photolysis of hydrogen peroxide&nbsp; (80%).&nbsp; Contrary&nbsp; to&nbsp; these&nbsp; results,&nbsp; under&nbsp; the&nbsp; same&nbsp; reaction&nbsp; conditions,&nbsp; a&nbsp; higher&nbsp; doses&nbsp; of AlFeB catalyst (0.1 g) is needed at lower pH value&nbsp; of the reaction, and the process efficiency is significantly dependent on the initial concentration of H ₂O₂. The fact that in the preparation of the catalysts bentonite as a natural, abundant, inexpensive material was used and solar&nbsp; radiation as a renewable and alternative source of photons, the above results should&nbsp; be taken into account in the cost-effectiveness&nbsp; analysis&nbsp; of&nbsp; the&nbsp; applied&nbsp; process. Also,&nbsp; the&nbsp; application&nbsp; of&nbsp; advanced&nbsp; oxidation processes is considered as a proposal&nbsp; for the best available technique when it comes to the treatment of&nbsp; wastewater&nbsp; from&nbsp; the&nbsp; textile&nbsp; industry,&nbsp; while&nbsp; as&nbsp; additional&nbsp; new&nbsp; techniques,&nbsp; photooxidation&nbsp; is considered as a candidate and the possibility of their application in the treatment of wastewater in tertiary treatment on semi-industrial systems.</p>

No description available.

L'utilisation du procédé d'oxydation avancée électrochimique : procédé électro-Fenton est un moyen simple et économique d'obtention des radicaux hydroxyles (OH*) fortement oxydantes. Au cours de ce travail les radicaux ont été utilisés pour la dégradation du chlortoluron, du carbofurane et du bentazone en solution aqueuse. La méthodologie de la recherche expérimentale a été utilisée pour étudier l'influence de quelques paramètres (concentration du chlortoluron, l'intensité du courant et la durée du traitement.) sur la vitesse de disparition et pour déterminer les conditions optimales de minéralisation. L'évolution de la concentration des pesticides en fonction du temps de traitement montre une cinétique de pseudo premier ordre (kabs = 4,92 × 109, 3.24 × 109 et 2.63 × 109 M-1 s-1 respectivement pour le chlortoluron, le carbofurane et le bentazone). Dans nos conditions expérimentales optimales (I = 300 mA, [pesticide]0 = 0,125 mM et t = 8 h), nous obtenons un taux de minéralisation supérieur à 90% pour les trois pesticides. Dans le cas des molécules étudiées, il a été montré que le taux de minéralisation par le procédé photo-Fenton (UV/Fe3+/H2O2) est fonction des doses des réactifs utilisés et de la concentration initiale des pesticides à traiter. Une comparaison des performances de minéralisation par les différents procédés étudiés (électro-Fenton (BDD), électro-Fenton (PT), oxydation anodique et photo-Fenton) a montré que les procédés photo-Fenton et électro-Fenton (BDD) permettent d'atteindre des taux de minéralisation très importants (˜ 90% au bout de 2 h). La comparaison du coût du traitement montre que le procédé photo-Fenton coûte beaucoup plus chère que le procédé électro-Fenton (BDD). Le plasma d'air humide a été utilisé pour la dégradation du chlortoluron. Différents catalyseurs (Fe2+, Fe3+ et TiO2) ont été étudiés pour améliorer les performances du glidarc. La combinaison entre TiO2 et Fe2+ permet d'aboutir à 96% de la dégradation du chlortoluron au bout de 3h

L’utilisation du procédé d'oxydation avancée électrochimique : procédé électro-Fenton est un moyen simple et économique d’obtention des radicaux hydroxyles (OH•) fortement oxydantes. Au cours de ce travail les radicaux ont été utilisés pour la dégradation du chlortoluron, du carbofurane et du bentazone en solution aqueuse. La méthodologie de la recherche expérimentale a été utilisée pour étudier l’influence de quelques paramètres (concentration du chlortoluron, l’intensité du courant et la durée du traitement.) sur la vitesse de disparition et pour déterminer les conditions optimales de minéralisation. L’évolution de la concentration des pesticides en fonction du temps de traitement montre une cinétique de pseudo premier ordre (kabs = 4,92 × 109, 3.24 × 109 et 2.63 × 109 M-1 s-1 respectivement pour le chlortoluron, le carbofurane et le bentazone). Dans nos conditions expérimentales optimales (I = 300 mA, [pesticide]0 = 0,125 mM et t = 8 h), nous obtenons un taux de minéralisation supérieur à 90% pour les trois pesticides. Dans le cas des molécules étudiées, il a été montré que le taux de minéralisation par le procédé photo-Fenton (UV/Fe3+/H2O2) est fonction des doses des réactifs utilisés et de la concentration initiale des pesticides à traiter. Une comparaison des performances de minéralisation par les différents procédés étudiés (électro-Fenton (BDD), électro-Fenton (PT), oxydation anodique et photo-Fenton) a montré que les procédés photo-Fenton et électro-Fenton (BDD) permettent d’atteindre des taux de minéralisation très importants (˜ 90% au bout de 2 h). La comparaison du coût du traitement montre que le procédé photo-Fenton coûte beaucoup plus chère que le procédé électro-Fenton (BDD). Le plasma d’air humide a été utilisé pour la dégradation du chlortoluron. Différents catalyseurs (Fe2+, Fe3+ et TiO2) ont été étudiés pour améliorer les performances du glidarc. La combinaison entre TiO2 et Fe2+ permet d’aboutir à 96% de la dégradation du chlortoluron au bout de 3h / The use of advanced oxidation electrochemical process: Electro-Fenton is an easy and economical way to obtain hydroxyl radical (•OH) strongly oxidizing. During this work radicals were used for the degradation of chlortoluron, carbofuran and bentazon in aqueous medium. The methodology of experimental research has been used to study the influence of some parameters (initial concentration, current intensity and processing time) on the rate of degradation and to determine the optimum conditions for mineralization. The evolution of chlortoluron concentration with processing time shows a pseudo first order kinetics ( (4.92 × 109, 109 × 3.24 × 2.63 and 109 M-1 S-1 respectively for the chlortoluron, and Carbofuran bentazon). In our optimal conditions (pH = 3, I = 300 mA, [pesticide]0 = 0.125 mM and t = 8 h), we obtain a TOC removal ratio more than 90% for the three pesticides. In the case of molecules studied, it was shown that the rate of mineralization by the photo-Fenton (UV/Fe3+/H2O2) is a function of doses of reagents used and the initial concentration of pesticides treaty. A comparison of the performance of mineralization by the different processes studied (Electro-Fenton (BDD), Electro-Fenton (PT), anodic oxidation and photo-Fenton) has shown that more than 90% of TOC removal was obtained after only 2 hours of photo-Fenton and electro-Fenton (BDD) process. Nevertheless, a comparison of the cost treatment shows that photo-Fenton process is more expensive than electro-Fenton (BDD). The plasma humid air was used for chlortoluron degradation. Different catalysers (Fe2+, Fe3+ and TiO2) were studied to improve the glidarc performances. The combination of TiO2 and Fe2+ can reach 96% of chlortoluron degradation after 3h

Des solutions d'acides carboxyliques contenant principalement de l'acide formique sont obtenues par oxydation photo-Fenton des polysaccharides. Une irradiation dans le visible de 60 W sous des conditions douces suffit à fournir des résultats reproductibles. Les produits d'oxydation issus d'amidon de pomme de terre et d'amidon de blé ont montré des capacités de complexation comparables aux solutions commerciales d'acide gluconique et glucuronique.Un système d'oxydation innovant, comprenant des sels d'halogénures et du DMSO, convertit quantitativement le HMF en DFF. Cette méthode permet aussi la transformation one-pot du fructose en DFF avec de bons rendements. Selon l'étude mécanistique, le bromo-HMF serait un intermédiaire réactionnel. / Solutions of carboxylic acids, containing mainly formic acid, are produced under photo-Fenton conditions. Visible irradiation with a 60 W spot is sufficient to provide reproducible results under mild conditions. The oxidation products of potato starch and wheat starch have shown Ca sequestering properties similar to those of gluconic and glucuronic acids.Using halide salts and DMSO, an innovating method has been elaborated for the selective oxidation of HMF to DFF with quantitative yields. The one-pot transformation of fructose to DFF occurs with fair yields. Based on the mechanistic study, Br-HMF would be the reaction intermediate.

O objetivo desta pesquisa foi estudar a degradação,pelo processo foto-Fenton, de um poluente-modelo (um antibiótico da classe dos nitrufuranos:a nitrofurantoína), utilizando-seLEDs-UV no lugar das lâmpadas tradicionalmente utilizadas, ou seja, das lâmpadas fluorescentes negras.Foram comparadas duas câmaras de irradiação, cada uma com um tipo de fonte, em termos de: porcentagem de remoção, ecotoxicidade (Lactuca sativa), atividade antimicrobiana (Escherichia coli), custos de capital (equipamentos), de operação (consumo energético) e das fontes luminosas, além do espaço ocupado. Os experimentos de degradação foramrealizados e otimizados via planejamento experimental, utilizando-se a Metodologia de Superfície de Resposta, obtendo-se as concentrações ótimas denitrofurantoína, de íons férricoe de peróxido de nitrogênio para cada caso.As câmaras estudadas apresentaram desempenhos semelhantes na remoção de nitrofurantoína (mais de 95% em 15 min), além de não ter havido a geração de produtos ecotóxicos (Lactuca sativa) e de ter sido alcançada a inativação biológica (Escherichia coli) do fármaco.A câmara de irradiação com LEDs é compacta, custa duas vezes menos que a outra e é quatro vezes mais eficiente em termos de consumo elétrico. A única desvantagem encontrada foi o custo dos LEDs-UV. Levando-se em conta o número de LEDs e de lâmpadas fluorescentes negras nas câmaras, o custo é trinta vezes maior. No entanto, o custo adicional dos LEDs-UV em relação às lâmpadas fluorescentes negras é facilmente compensado pela economia realizada nos custos de capital (aquisição do equipamento) e de operação (consumo energético).Em suma, pelo menos no caso da degradação da nitrofurantoína pelo processo foto-Fenton, os LEDs-UV mostraram-se substitutos vantajosos das lâmpadas fluorescentes negras, tradicionalmente utilizadas. / The goal of this research was to study the degradation, by the photo-Fenton process, of a model-pollutant (an antibiotic fromthe nitrofurans group: nitrofurantoin), using UV-LEDs instead of the lamps traditionally used, i.e. black fluorescent lamps. Two irradiation chambers were compared, each one of them with a type of light source, regarding: removal percentage, ecotoxicity (Lactuca sativa), antimicrobial activity (Escherichia coli), capital costs (equipment), operating costs (energy consumption), and light sources costs, as well as the space the chambers occupy.The degradation experiments were performed and optimized by experimental design, using the Response Surface Methodology, and obtaining the optimum concentrations of nitrofurantoin, ferric ions, and hydrogen peroxide, for each of the chambers. The studied chambers showed similar performances regarding nitrofurantoin removal (more than 95% in 15 min), besides the generation of no ecotoxic products (Lactuca sativa) and the biological inactivation (Escherichia coli) of the drug. The irradiation chamber with UV-LEDs is compact,cheaper (it is half of the price of the other one), and it is four times more efficient in terms of electric consumption. The sole disadvantage found was the cost of the UV-LEDs. Taking into consideration the number of LEDs and black fluorescent lamps used in the chambers, thiscost is 30 times greater. However, the additional cost of the UV-LEDsin comparison to black fluorescent lamps is easily compensated by the savings in capital costs (equipment acquisition) and operating costs (electric consumption). In summary, at least regarding the nitrofurantoin degradation by the photo-Fenton process, the UV-LEDs proved to beworthwhile alternatives for black fluorescent lamps, which are traditionally used.

Neste trabalho, utilizou-se um Processo Oxidativo Avançado (POA) para a degradação de uma solução aquosa contendo uma mistura de metilparabeno e propilparabeno (50 &mu;g L-1 cada). O processo estudado foi o foto-Fenton solar, em um reator do tipo CPC operado no modo batelada com reciclo total. As condições operacionais foram otimizadas por meio da Metodologia de Superfície de Resposta (MSR), sendo elas: 771,6 &mu;g H2O2 L-1, 65,3 &mu;g Fe3+ L-1 e vazão 0,9 L min-1. O pH foi fixado em 2,5. A determinação das concentrações dos analitos foi realizada por Cromatografia Líquida de Alta Eficiência acoplada a um Detector de Arranjo de Diodos (CLAE-DAD), tendo sido monitorado o comprimento de onda 258 nm. Utilizou-se como técnica extratora e de pré-concentração a Microextração Líquido-Líquido Dispersiva (MELLD), sendo o n-octanol o solvente extrator e a acetona o solvente dispersivo. Avaliou-se a cinética de degradação do processo otimizado (em triplicata), obtendo-se uma degradação &gt; 99% em 50 min. As constantes de taxa (em função da dose de energia, unidades m² kW-1) foram 1,2 &plusmn; 0,034 (R² = 0,987) e 1,1 &plusmn; 0,042 (R² = 0,979) para o metilparabeno e o propilparabeno, respectivamente. O efluente do reator mostrou-se biologicamente inativo, tendo sido testadas sua ecotoxicidade (Lactuca sativa) e sua atividade antimicrobiana (Escherichia coli). / In this work, an Advanced Oxidation Process (AOP) was used for the degradation of aqueous methylparaben and propylparaben (50 &mu;g L-1 each). The studied process was the solar photo-Fenton reaction, using a CPC-type reactor, which was operated in batch mode with total recycle. The experimental conditions were optimized using the Response Surface Methodology (RSM) and the obtained results were: 771.6 &mu;g H2O2 L-1, 65.3 &mu;g Fe3+ L-1, and flow rate 0,9 L min-1. The solution pH was set at 2.5. The analytes concentration were determined by High Efficiency Liquid Chromatography coupled to a Diode-Array Detector (HPLC-DAD), monitoring the 258 nm wavelength. The Dispersive Liquid-Liquid Extraction was used as a pre-concentration and extraction technique before injection, whereas n-octanol was the extraction solvent and acetone was the dispersive one. The optimized degradation process kinetics was assessed (triplicate) and more than 99% degradation was obtained after 50 min. The rate constants (normalized by the energy dose, m2 kW-1 units) were 1.2 &plusmn; 0.034 (Rsup>2 = 0.987) and 1.1 &plusmn; 0.042 (R2 = 0.979) for methylparaben and propylparaben, respectively. The reactor effluent was biologically inactive, regarding its ecotoxicity (Lactuca sativa) and antimicrobial activity (Escherichia coli).

Este trabalho de mestrado descreve a avaliação do emprego de radicais sulfato (SO42-.), obtidos a partir do oxidante persulfato de potássio (K2S2O8) , na degradação de soluções aquosas de fenol. A deterioração dos recursos hídricos tem assumido um caráter preocupante uma vez que as demandas deste bem estão se tornando cada vez maiores. Dentre os compostos responsáveis pela degradação da qualidade dos sistemas aquáticos, destacam-se os compostos orgânicos poluentes como os organoclorados, organofosforados, carbamatos, triazinas, hidrocarbonetos aromáticos polinucleares, fenólicos, etc. Dentre esta série de compostos poluentes, atenção especial tem sido dada ao fenol devido as grandes quantidades em que são gerados e pela diversidade tipos de atividades produtivas que o empregam. Assim, este trabalho avaliou a aplicação de radical SO4 2- do fenol Estudos utilizando ressonância paramagnética eletrônica (EPR) mostraram que o radical SO42- é a principal espécie radicalar obtida a partir da fotólise e termólise do oxidante S2O8-2. A presença de radiação UV contribuiu beneficamente para a degradação do composto orgânicos. Altas temperaturas como 40 0C e 70 <SÙP>0C também levaram a uma maior taxa na degradação do fenol devido a uma maior produção de espécies radicalares oxidantes. Além dos processos fotoassistidos e térmicos, investigou-se também processos de geração dos radicais a partir da ativação do oxidante em diferentes pH (3,0, 5,0, 7,0 e 9,0) e tambem na presença de metais de transição (Co2+, Mn2+, Fe2+, Fe3+ e Cu2+). A processo não foi afetada pelo pH. Com relação a presença dos metais de transição na solução obteve-se um ganho na eficiência do processo principalmente com o emprego do Fe2+, caracterizando a reação como uma reação do tipo Fenton. De uma maneira geral a utilização de SO4 2- na degradação de fenol mostrou-se bastante promissora para uma aplicação deste processo no tratamento de efluentes contendo estes compostos. / This work describes the evaluation of radicals sulphate (SO42-), obtained from the oxidant potassium persulphate (K2S2O8), in the degradation of phenol aqueous solutions. The deterioration of the aquatic resources has been assumed a preoccupying situation, since a time its demands has been increased constantly. Amongst many compounds in the degradation of aquatic systems quality, special attention has been dispensed to organic compounds such as organochlorinated, organophosphorated, aromatic carbamates, triazines, polynuclear hydrocarbons, phenolic, etc. This work evaluated the application of SO42- radicals in the degradation of phenol. Studies using electron paramagnetic resonance (EPR) showed that SO4-2 is the main radical species obtained by the S2O8-2 oxidant photolysis and thermolysis. The presence of UV radiation contributed to improve phenol degradation due to the increase in oxidant radicals production. Higher temperatures (40 0C and 70 0C) have also led to an increment in the phenol degradation rate. Beyond the photoassisted and thermal processes, it was also investigated processes of radicals\' generation from the activation of the oxidant in different pH (3.0, 5.0, 7.0 and 9.0) and also in the presence of transition metals (Co2+, Mn2+ , Fe2+ , Fe3+ and Cu2+ ). The efficiency of the process was not affected by the pH. On the other hand, the presence of transition metals in the solution led to considerably better degradation rates, specially applying Fe2+, which could be characterized as a Fenton-like reaction. In a general way, the use of SO42- in the phenol degradation showed promising results for its future application in the treatment of effluent containing these composites.