This study investigated the photocatalytic reduction of CO2 in a self-designed closed circulated batch reactor system and a bench-scale batch photocatalytic reactor. The photocatalysts tested included titanium dioxide (TiO2, Degussa P-25) and zirconium oxide (ZrO2). The reductants investigated included hydrogen (H2), water vapor (H2O), and hydrogen plus water vapor (H2+H2O). The wavelengths of incident near ultra-violet (UV) and UV lights for the photocatalysis of TiO2 and ZrO2 were 365 nm and 254 nm, respectively. The initial concentrations of CO2 ranged from 0.2-5.0% and the reaction temperature ranged from 35-95 ¡³C. The incident near-UV (or UV) light with wavelength of 365 nm (or 254 nm) was irradiated by a 15-watt low-pressure mercury lamp. The photocatalytic reaction was conducted continuously for approximately two hours. Reactants and products were analyzed by a gas chromatography with a flame ionization detector followed by a methanizer (GC/FID-methanizer). Experimental results indicated that glass pellets coated with TiO2 had better photoreduction efficiency than ZrO2. The highest yield rates of the photoreduction of CO2 were obtained using TiO2 with H2+H2O and ZrO2 with H2. Photoreduction of CO2 over TiO2 with H2+H2O formed CH4, C2H6, and CO in the yield of 32.95~94.60, 0.80~18.55, 1.12~21.78 £gmol/g, respectively, while the photoreduction of CO2 over ZrO2 with H2 formed CO in the yield of 0.34~4.99 £gmol/g. Results obtained from the operating parameter tests showed that the photoreduction rate increased with the initial concentration of carbon dioxide and resulted in more product accumulation. The photoreduction rate of carbon dioxide increased with reaction temperature, which promoted the formation of products. Concurred with previous researches, the reaction rate of major products over TiO2 and ZrO2 were higher than previous investigations of CO2 photoreduction. Furthermore, the spectra of FTIR showed that formic acid (HCOOHads), methanol (CH3OHads), carbonate (CO32−ads), bicarbonate (HCO32−ads), formate (HCOO−ads), formic acid (HCOOH ads), formaldehyde (HCOHads) and methyl formate (HCOOCH3 ads) formed on the surface of TiO2 and ZrO2 photocatalysts. The detected reaction products supported the proposal of two reaction pathways for the photoreduction of CO2 over TiO2 and ZrO2 with H2 and H2O, respectively. A modified bimolecular Langmuir-Hinshelwood kinetic model was developed to simulate the reaction temperature, CO2 initial concentration and relative humidity promotion and inhibition of the photoreduction of CO2. Additionally, the modified L-H kinetic model was successfully applied to simulate the photoreduction rate of CO2. The result showed that CO2 could be reduced by used solar light over TiO2 and ZrO2 photocatalysts. The reaction products of CO2 photoreduction over TiO2 were CH4, C2H6, and CO in the yield of 2.16~2.995, 0.057~0.128, 0.078~0.134 £gmol/g, respectively, while the photoreduction of CO2 over ZrO2 formed only CO in the yield of 0.023~0.051 £gmol/g. Furthermore, experimental results indicated that TiO2 gave the highest average photo energy efficiency (AEf) of ~4.13%, and apparent quantum efficiency (£pA) of ~1.05%. However, the ZrO2 gave the highest average photo energy efficiency (AEf) of 5.07¡Ñ10-3%, and apparent quantum efficiency (£pA) of ~1.54¡Ñ10-2%.

La modification du TiO₂ P25 par un ou deux métaux a connu un intérêt considérable ces dernières années, car ils constituent des catalyseurs et photocatalyseurs très actifs à la fois sous lumière UV et visible. Des nanostructures à un ou deux métaux, comme Au, Ag, Ag@CuO et CuO déposés sur le TiO₂ P25 ont la capacité d’absorber la lumière visible sur un large domaine de longueurs d’onde. Le TiO₂ modifié par des nanoparticules métalliques (comme, Cu, Au ou Ag) absorbe la lumière visible grâce à la résonance de plasmon de surface localisée (LSPR) des métaux. Dans le cas d’une hétérojonction de semi-conducteurs, la lumière visible est absorbée grâce à l’énergie du gap plus faible du second semi-conducteur (par rapport à celle du TiO₂ P25). La modification par une ou deux nanoparticules métallique induit une plus grande activité photocaralytique sous lumière visible par rapport au TiO₂ P25 pur, par transfert d’électrons vers la bande de conduction du P25. De plus sous lumière UV, la vitesse de capture d’électrons photo-excités peut être améliorée, ce qui inhibe les processus de recombinaison et permet de stocker ces électrons photo-excités.Cette thèse présente une synthèse des récentes avancées dans la préparation de TiO₂ modifié en surface par un ou deux métaux et ses applications environnementales. Des nanoparticules d’or ont été synthétisées par une méthode chimique à partir de chlorure de tetrakis(hydroxymethyl) phosphonium (THPC), des nanoparticules de Ag, Ag@CuO et CuO ont été synthétisées sur TiO₂ par radiolyse. L’effet de nombreux paramètres (comme la taille et la forme des particules ou la quantité de métal déposé) sur l’activité photocatalytique (oxydation du phénol, du 2-propanol et de l’acide acétique et génération d’hydrogène) a été étudié. La dynamique de porteurs de charge a été étudiée par conductivité microonde résolue en temps (TRMC). / The modification of TiO₂-P25 with one or two metal-based nanoparticles, have attracted considerable attention in recent years, as a new class of highly active catalysts and photocatalysts under both UV and visible light irradiation. One or two-metal-based structures, such as Au, Ag, Ag@CuO and CuO deposited on TiO₂-P25 have the ability to absorb visible light in a wide spectral range. Surface modified TiO₂ with metal nanoparticles (such as Cu, Au, Ag) absorb visible light due to the localized surface plasmon resonance (LSPR). In the case of semiconductor heterojunctions, they absorb visible light due to the narrow band gap of the second semiconductor, lower than TiO₂-P25. The modification with one or two metal-based nanoparticles induces a higher activity under visible light compared to pure TiO₂-P25, due to the transfer of electrons to the conduction band of TiO₂-P25. On the other hand, under UV irradiation, the speed of trapping photoexcited electrons can be improved, and inhibit the recombination process and have the capability of the storage of photoexcited electrons.This thesis presents recent advances in the preparation and environmental application of the surface modification of TiO₂-P25 with one or two-metal-based nanoparticles: The Au-NPs were synthesized by chemical method using tetrakis(hydroxymethyl) phosphonium chloride (THPC), and the nanoparticles of Ag, Ag@CuO and CuO-NPs were synthesized by gamma irradiation. Moreover, the effects of various parameters (such as particle size, shape of the nanoparticles and amount of metals) on the photocatalytic activity (phenol, 2-propanol and acetic acid oxidation, as well as hydrogen generation) were also studied. The charge carrier dynamics was studied by time resolve microwave conductivity (TRMC).

A solar fiber optic lighting system, SP3 from the Swedish company Parans Solar Lighting AB, has been installed in a study area/corridor test site. A collector is tracking the sun during daytime, focusing the direct sun irradiance via Fresnel lenses into optical fibers, which guide the solar light into the building. The illumination properties of the system have been characterized. The energy saving due to reduced need of artificial lighting have been calculated and methods for balancing the artificial lights in the test site have been evaluated. The illumination at the test site using solar light was at least as high as when using the artificial lights and even higher at very clear days. The luminous flux output (500 lm) was somewhat lower than specified by the manufacturer (550 lm) at 100 000 lx direct sun illuminance. The output at 130 000 lx was high 767±33 lm the sunlight coupling efficiency 23 %. However, for a 20 m SP3 system the luminous flux output (400 lm) at 100 000 lx was higher than specified (350 lm). The SP3 system of Parans provides high quality solar light. It has a fuller spectrum close to the spectrum of the sun compared to the fluorescent lights at the test site. The correlated color temperature of the system was 5800±300 K and the color rendering index 84.9±0.5. The lighting energy saved due to decreased need for artificial light was estimated to 19 % in Uppsala which has 1790 annual sun hours. The savings in Italy, which has 3400 sun hours, is 46 %. Additional saving, especially in warmer countries can be obtained due to decreased need for cooling in the building as the solar luminaires provide negligible heat to the indoor air. Economical saving could also be realized by improved well-being of the occupants spending time under the solar luminaires. Three ways of balancing the artificial light due to sunshine fluctuations have been investigated. The global horizontal irradiance could not be used as a control signal for balancing the artificial lights but a pyranometer attached to the SP3 sun tracking collector was usable. Also the signal from an indoor luxmeter sensor could be used for balancing the light. However the signal from the light sensor which makes the SP3 collector to track the sun is probably the most cost effective method as it would serve two purposes; tracking the sun and balancing the artificial lights.

La présente thèse, concernant l’ingénierie de la photosynthèse naturelle et notamment l’optimisation des procédés de production de microalgues, a été menée à l'Institut Pascal. L'approche suivie repose sur la construction de modèles de connaissance des photobioréacteurs, capables d'en prédire les performances quelle que soit leur géométrie, les conditions d'éclairement, ou le type de microalgues cultivées. Ces modèles de connaissance permettent de dégager des stratégies de conception et de conduite du procédé, qui sont utilisées pour développer et réaliser des démonstrateurs performants, à l'échelle pilote. Cette thèse a pour objet d'étude un photobioréacteur pilote de 24 litres utiles à agitation pneumatique dans lequel la lumière est apportée dans le volume réactionnel par 1000 fibres optiques à diffusion latérale. Sa conception repose sur le principe innovant de Dilution Contrôlée du Flux solaire en Volume (DiCoFluV) dont l'objectif est d'atteindre l'efficacité thermodynamique maximale de la photosynthèse. Au cours de cette thèse, le réacteur a été étudié en conditions d’éclairement parfaitement contrôlées, grâce à des lampes à décharges. Il a été rendu fonctionnel (en incluant sa régulation et son amélioration), puis caractérisé en termes d'hydrodynamique et de transfert radiatif. Notamment, le flux radiatif incident à la surface des fibres optiques a été déterminé par des expériences d'actinométrie (sel de Reinecke), grâce à un traitement original permettant l'analyse de situations avec absorption partielle du rayonnement et en géométrie complexe. Ensuite, une année de culture ininterrompue de la cyanobactérie Arthrospira platensis (dont six phases de fonctionnement continu) ont permis de mesurer la vitesse volumétrique moyenne de production de biomasse et l'efficacité thermodynamique du pilote. Pour les faibles densités de flux testées (dilution), les résultats expérimentaux ont montré l’apparition d’un phénomène de photorespiration qui a été intégré dans le modèle de couplage thermocinétique. De plus, ce manuscrit présente également l'utilisation de la méthode de Monte Carlo pour la résolution des modèles radiatifs dans la géométrie réelle du procédé, définie à partir d’une conception assistée par ordinateur, ce qui est une nouvelle avancée pour le traitement des géométries complexes. Après validation de l'adéquation entre les mesures expérimentales et l'estimation prédictive par le modèle, des premières simulations du pilote en fonctionnement solaire ont été menées, à partir de bases de données solaires (DNI). Les résultats obtenus donnent des premières indications quant aux paramètres d'ingénierie (en particulier le facteur de dilution) menant à une productivité surfacique moyenne annuelle maximale, en fonction de l'implantation géographique. / The present PhD dissertation deals with photobioreaction engineering for efficient microalgae production. The approach is based on the construction of knowledge models that permit predicting the performances of the process, whatever its design, the illumination conditions, or the microalgae species cultivated. These models are used to establish optimal design and control strategies that are implemented to construct and operate pilot-scale plants. Here, a 24 liters air-lift photobioreactor is studied, that is based on the principle of incident solar light-flux dilution for approaching the maximum thermodynamic efficiency of natural photosynthesis. For that purpose, the culture volume is internally illuminated by 1000 light-diffusing optical fibers. As a first step toward solar production, this PhD work focuses on perfectly controlled illumination conditions ensured by discharge lamps. First, the reactor hydrodynamics and radiative transfer are characterized. In particular, incident light-flux density at the fiber surfaces is measured by actinometry (with Reinecke salt), thanks to a novel treatment enabling analyses of situations with partial light absorption and complex geometries. Then, the mean volumetric rate of biomass production and the process efficiency are measured based on one year of continuous Arthrospira platensis culture. For the low radiative flux densities tested (dilution), photorespiration by the cyanobacterium is observed and included in the thermokinetic model. Moreover, this dissertation includes a presentation of the Monte Carlo method for solving the radiative transfer equation withinthe complex geometry of the computer aided design used for manufacturing the reactor. After validation against experimental results, the model is predictively used to simulate the pilot operating with natural solar light, based on solar DNI databases. These results indicate engineering parameters (in particular the dilution factor) for optimal yearly-averaged surface productivity, as a function of Earth location.

O grande impacto ambiental causado pelo chorume proveniente de aterros sanitários impulsiona as pesquisas para o seu tratamento, com o objetivo de se obter a máxima degradação possível dos seus contaminantes recalcitrantes e tóxicos, diminuindo-se assim a sua toxicidade. O desenvolvimento de uma tecnologia eficiente e econômica para o tratamento é indispensável devido ao grande volume gerado e à legislação ambiental cada vez mais restritiva. Desta forma, os Processos Oxidativos Avançados (POAs) são avaliados como uma estratégia para o pré-tratamento, com um alto poder de degradação não seletivo e relação custo-benefício vantajosa. Dos diversos tipos de POAs existentes, aqueles que utilizam semicondutores para a fotocatálise heterogênea e luz solar como fonte de irradiação são os de maior interesse, devido a sua relativa eficiência, estabilidade fotoquímica, natureza não tóxica e baixo custo. Este estudo consistiu em avaliar o nível de degradação do chorume proveniente do aterro sanitário de Cachoeira Paulista - SP, utilizando como catalisador o ZnO irradiado pela luz solar, que possui um vasto espectro de fotoativação aliado ao seu baixo custo. As variáveis de entrada em dois níveis, foram o pH, o tempo de reação, a espessura da camada de ZnO impregnada sobre uma placa metálica e a concentração do efluente. Como variável resposta os valores de concentração expressa em Carbono Orgânico Total (COT) foi a mais adequada. O planejamento de experimentos utilizado foi o fatorial 23 com duplicata no ponto central. Na etapa delineatória, reduções de 28 % de COT foram alcançadas. A utilização da fotocatálise heterogênea utilizando ZnO fotoirradiado com luz solar se mostrou promissora para ser utilizada como um pré-tratamento do chorume. / The major environmental impact of leachate from landfills drives research to treat it, and aims to obtain the maximum degradation of their recalcitrant and toxic contaminants. The development of an efficient and economical treatment technology is indispensable due to the large volume generated and the increasingly restrictive environmental legislation. Thus, Advanced Oxidation Processes (AOPs) are evaluated as a strategy to pre-treatment with a high power non-selective degradation and advantageous cost-benefit ratio. From various types of POAs, those which use the heterogeneous photocatalytic semiconductor and solar light as the source of irradiation are the most interesting, because of its relative efficiency, photochemical stability, low cost and non-toxic nature. This study have assessed the level of degradation of the leachate from the landfill of Cachoeira Paulista - SP, using ZnO irradiated by sunlight as catalyst, which has a wide spectrum of photoactivation combined with its low cost. The input variables on two levels, were pH, reaction time, the thickness of the ZnO layer impregnated on a metal plate and concentration of the effluent. The most appropriate output variable was concentration, expressed in means of Total Organic Carbon (TOC). For the photocatalytic process, a factorial design (23) was used for the design of experiments. In final stage, reductions of 28% TOC were achieved. The use of heterogeneous photocatalysis using solar photoirradiated ZnO seems to be a great alternative as a pre-treatment of leachate.

O grande impacto ambiental causado pelo chorume proveniente de aterros sanitários impulsiona as pesquisas para o seu tratamento, com o objetivo de se obter a máxima degradação possível dos seus contaminantes recalcitrantes e tóxicos, diminuindo-se assim a sua toxicidade. O desenvolvimento de uma tecnologia eficiente e econômica para o tratamento é indispensável devido ao grande volume gerado e à legislação ambiental cada vez mais restritiva. Desta forma, os Processos Oxidativos Avançados (POAs) são avaliados como uma estratégia para o pré-tratamento, com um alto poder de degradação não seletivo e relação custo-benefício vantajosa. Dos diversos tipos de POAs existentes, aqueles que utilizam semicondutores para a fotocatálise heterogênea e luz solar como fonte de irradiação são os de maior interesse, devido a sua relativa eficiência, estabilidade fotoquímica, natureza não tóxica e baixo custo. Este estudo consistiu em avaliar o nível de degradação do chorume proveniente do aterro sanitário de Cachoeira Paulista - SP, utilizando como catalisador o ZnO irradiado pela luz solar, que possui um vasto espectro de fotoativação aliado ao seu baixo custo. As variáveis de entrada em dois níveis, foram o pH, o tempo de reação, a espessura da camada de ZnO impregnada sobre uma placa metálica e a concentração do efluente. Como variável resposta os valores de concentração expressa em Carbono Orgânico Total (COT) foi a mais adequada. O planejamento de experimentos utilizado foi o fatorial 23 com duplicata no ponto central. Na etapa delineatória, reduções de 28 % de COT foram alcançadas. A utilização da fotocatálise heterogênea utilizando ZnO fotoirradiado com luz solar se mostrou promissora para ser utilizada como um pré-tratamento do chorume. / The major environmental impact of leachate from landfills drives research to treat it, and aims to obtain the maximum degradation of their recalcitrant and toxic contaminants. The development of an efficient and economical treatment technology is indispensable due to the large volume generated and the increasingly restrictive environmental legislation. Thus, Advanced Oxidation Processes (AOPs) are evaluated as a strategy to pre-treatment with a high power non-selective degradation and advantageous cost-benefit ratio. From various types of POAs, those which use the heterogeneous photocatalytic semiconductor and solar light as the source of irradiation are the most interesting, because of its relative efficiency, photochemical stability, low cost and non-toxic nature. This study have assessed the level of degradation of the leachate from the landfill of Cachoeira Paulista - SP, using ZnO irradiated by sunlight as catalyst, which has a wide spectrum of photoactivation combined with its low cost. The input variables on two levels, were pH, reaction time, the thickness of the ZnO layer impregnated on a metal plate and concentration of the effluent. The most appropriate output variable was concentration, expressed in means of Total Organic Carbon (TOC). For the photocatalytic process, a factorial design (23) was used for the design of experiments. In final stage, reductions of 28% TOC were achieved. The use of heterogeneous photocatalysis using solar photoirradiated ZnO seems to be a great alternative as a pre-treatment of leachate.

Die Verwendung von pharmazeutischen Wirkstoffen (API) hat die moderne medizinische Behandlung erneuert und die menschliche Gesundheit vor Infektionskrankheiten geschützt. Andererseits werden Wirkstoffe in der Regel über Krankenhausabwässer oder Industrieabwässer in verschiedene Gewässer eingeleitet. Ihr kontinuierlicher Eintrag in die Umwelt hat eine ausgeglichene Umwandlungs-/Eliminierungsrate zur Folge und macht API zu 'pseudo-persistenten' Schadstoffen. Antibiotika gehören zur Gruppe der Wirkstoffe und werden in großem Umfang in Rohwasserquellen für Trinkwasser nachgewiesen. Die Konzentration der im Abwasser nachgewiesenen pharmazeutischen Verunreinigungen reicht von ng/L bis µg/L. Ciprofloxacin (CIP) wurde in Abwasser in extrem hohen Konzentrationen (bis zu 31 mg/L) nachgewiesen, die tausendmal höher sind als die für einige Bakterien toxischen Konzentrationen und es zum häufigsten Arzneimittel in Abwasser machen. Die zunehmende Konzentration von Antibiotika ist der Hauptgrund für die Entwicklung antibiotikaresistenter Bakterien, die eine Vielzahl von antibiotikaresistenten bakteriellen Infektionen verursachen. Von vielen pharmazeutischen Instituten wurde erwartet, dass sie neue Antibiotika entwickeln, um die antibiotikaresistenten Bakterien zu bekämpfen. Viele Studien über neue Antibiotika werden jedoch aufgrund der hohen Kosten und des Mangels an Innovation aufgegeben. Somit sind Antibiotika und antibiotikaresistente Bakterien widerspenstige Schadstoffe, die Anlass zu großer Sorge geben. Verschiedene konventionelle und moderne Techniken wie Ozonierung, Nanofiltration und biologische Methoden wurden zur Beseitigung von Schadstoffen eingesetzt. Dennoch sind teure Infrastrukturen, komplexe Systeme und ein hoher Bedarf an Platz und Energie (Strom, Gas) für die Umsetzung dieser Techniken erforderlich, die zudem nicht in der Lage sind, die in Spuren vorhandenen Schadstoffe zu entfernen. Daher werden fortgeschrittene Oxidationsverfahren (AOP) als interessante Lösung angesehen. AOPs sind chemische Behandlungen, die stark oxidierende Spezies, wie z. B. Hydroxylradikale, erzeugen können, um Schadstoffe in Abwässern abzubauen. Viele Studien wurden über den Einsatz der Photokatalyse durchgeführt, die eine der wichtigsten Untergruppen der AOPs ist. Die populärsten Photokatalysatoren, wie z.B. Halbleiter, werden seit dem zwanzigsten Jahrhundert wegen ihrer hohen photokatalytischen Effizienz und ihrer geringen Kosten in der Abwasserbehandlung eingesetzt. Allerdings haben diese Photokatalysatoren auch ihre Grenzen. Titandioxid, der am häufigsten verwendete Photokatalysator und Halbleiter mit großer Bandlücke, hat eine Bandlücke von 3,0 eV in der Rutilphase und 3,2 eV in der Anatasphase. Daher kann er hauptsächlich unter UV-Bestrahlung - die nur 4-5 % des Sonnenlichts ausmacht - photoaktiviert werden und erfordert den Einsatz künstlicher UV-Lichtquellen, um einen effizienten Photoabbau zu erreichen. Der Bedarf an externen Lichtquellen ist immer mit einem hohen Energiebedarf verbunden. Die weltweite Verknappung von Erdöl und Erdgas hat zu einer weit verbreiteten Besorgnis über die Energieversorgung geführt, da ein kalter und dunkler Winter befürchtet wird, insbesondere in der kritischen Situation der zunehmenden globalen Energiekrise. Diese Sorgen haben die Entwicklung alternativer, nachhaltiger Energiequellen in den Mittelpunkt gerückt. Die Lösung für all diese Probleme ist die Nutzung der Sonnenenergie. Eine florierende Forschung hat sich mit der Entwicklung von photokatalytischen Systemen beschäftigt, die im sichtbaren Bereich arbeiten. Allerdings machen ultraviolettes (UV) und sichtbares Licht zusammen nur die Hälfte der Photonen des Sonnenspektrums aus. Die verbleibenden Photonen im nahen Infrarot (NIR) werden für die Energieumwandlung noch zu wenig genutzt. Die Entwicklung praktischer Strategien zur Nutzung des NIR-Lichtanteils der Sonne ist von entscheidender Bedeutung, um die photokatalytische Effizienz für künftige industrielle Anwendungen zu erhöhen. Die Rückgewinnung und Wiederverwendung der verwendeten partikelförmigen Materialien ist ein weiterer mühsamer Schritt. Wie in neueren Studien beschrieben, erfordern die Partikeltrennverfahren höhere Kosten und komplizierte Systeme. Die Immobilisierung der Partikel auf einer Oberfläche wurde untersucht, wobei sich die Nachteile einer begrenzten Adsorptionsfläche und eines unzureichenden Kontakts mit Verunreinigungen oder Sekundärverschmutzungen durch das Auslaugen der Partikel aus den Trägermaterialien gezeigt haben. Ziel dieser Arbeit ist es, einen neuen Ansatz zur Herstellung effizienter solarbetriebener Tm3+-Photokatalysatoren auf UCNP-Basis zu demonstrieren, die aus relativ kostengünstigen Ausgangsstoffen (Poly(vinylalkohol) (PVA), Poly(acrylsäure) (PAA), Poly(etheretherketon) (PEEK)) und Spurenmengen von Lanthanidionen bestehen. Die Nanokomposit-Matrix besteht aus PVA und hydroxyliertem sulfoniertem PEEK (SPOH), die mit PAA-dekorierten UCNPs durch eine einfache Erhitzung bei 170 °C vernetzt wurden, was zu einem nicht auslaugenden porösen UCNP-Material führte. Die in die PVA/SPOH-Matrix eingebetteten UCNPs waren in der Lage, NIR-Licht zu absorbieren und die nach oben konvertierende Anregungsenergie auf die Polymermatrix zu übertragen, was zur Produktion von H2O2 (7,0-10-8 mol-L-1*min-1) führte. Dieses Material erwies sich auch unter Sonneneinstrahlung als funktionsfähig. Der so hergestellte Photokatalysator zeigte eine ausgezeichnete Adsorption (89%) und einen photokatalytischen Abbau (50%) in 4 Stunden gegenüber CIP sowie eine vielversprechende photokatalytische bakterizide Wirkung (55% in 1 Stunde) gegenüber E. coli unter Sonneneinstrahlung. Insgesamt deuten diese Ergebnisse darauf hin, dass dieses Nanokomposit den Weg für ein solarbetriebenes Abwasserreinigungsverfahren auf der Grundlage von hochkonvertierenden Nanopartikeln ebnen kann.

Os processos oxidativos avançados (POAs) têm sido apontados como alternativa eficiente para a degradação de poluentes recalcitrantes. Entre os POAs, a fotocatálise utilizando luz solar vem sendo muito estudada tendo em vista sua aplicação no tratamento de efluentes aquosos contendo pesticidas. No presente trabalho, estudou-se a degradação do herbicida amicarbazona (AMZ) por meio do processo TiO2/UV em um reator com coletores parabólicos compostos irradiados por luz solar. Os experimentos foram realizados segundo uma matriz Doehlert para o estudo da influência da concentração inicial de AMZ (20-100 mg L-1), da concentração de catalisador (0,1-1 g L-1) e do número de tubos expostos à luz solar (1-9). Amostras retiradas ao longo do tempo foram analisadas quanto às concentrações de AMZ e de carbono orgânico total (TOC). As medidas radiométricas realizadas indicaram que a radiação UVB-UVA correspondeu em média a ca. 4% da radiação solar total incidente entre 310-2800 nm; a actinometria de ferrioxalato indicou fluxo fotônico médio de 3,58×10-5 mol fótons m-2 s-1 para dias ensolarados típicos. O processo TiO2/UV mostrou-se eficiente para degradação do pesticida, que foi totalmente removido antes de 45 minutos de tratamento, para as seguintes condições: [AMZ]0=21,3 mg L-1; [TiO2]=0,5 g L-1; e 7 tubos. Contudo, nesse caso houve apenas ca. 24% de mineralização e na grande maioria dos casos os valores de TOC permaneceram praticamente constantes, o que indica a formação de sub-produtos recalcitrantes, cuja toxicidade e biodegradabilidade devem ser caracterizadas. A análise estatística dos resultados confirma os efeitos importantes da concentração inicial do pesticida e do número de tubos expostos (volume irradiado), cujo aumento permite compensar a menor incidência de radiação solar. Em alguns experimentos os resultados sugeriram que a degradação da AMZ foi favorecida pela maior concentração de TiO2. Na grande maioria dos casos os valores de ACM foram inferiores a 50 m2 kg-1, o que torna este parâmetro interessante para aumento de escala de processos fotocatalíticos irradiados por luz solar empregados no tratamento de efluentes aquosos contendo amicarbazona. / Advanced oxidative processes (AOP) have been considered as an efficient alternative for the degradation of recalcitrant pollutants. Photocatalysis using solar radiation has been studied for the treatment of wastewaters containing pesticides. In this work, the degradation of the herbicide amicarbazone (AMZ) by the TiO2/UV process was studied in a reactor equipped with compound parabolic collectors irradiated by solar light. The experiments were carried out according to a Doehlert matrix to study the effects AMZ initial concentration (20-100 mg L-1), catalyst concentration (0.1-1 g L-1), and number of tubes exposed to solar light (1-9). Samples were analyzed for AMZ and total organic carbon (TOC) concentrations. Radiometric measurements indicated that UVB-UVA radiation corresponded in average to about 4% of the solar radiation between 310-2800 nm; ferrioxalate actinometry resulted in an average photonic flux of 3.58×10-5 mol fótons m-2 s-1 for typical sunny days. The TiO2/UV process showed to be efficient for the degradation of the pesticide, which was completely removed before 45 minutes of treatment, for the following conditions: [AMZ]0=21.3 mg L-1; [TiO2]=0.5 g L-1; and 7 tubes. However, in this case only ca. 24% of mineralization was achieved, and in most cases TOC values remained practically constant, indicating the formation of recalcitrant by-products whose toxicity and biodegradility should be characterized. Statistical analysis of the results confirmed important effects of pesticide initial concentration and number of tubes exposed (irradiated volume), whose increase enables to compensate the lower incidence of solar radiation. Some experimental results suggested that AMZ degradation was favored by higher TiO2 concentrations. In most cases the values of ACM were lower than 50 m2 kg-1, in such a way that this parameter is interesting for scale-up of solar irradiated photocalytic processes used in the treatment of amicarbazone-containing wastewaters.

Os processos oxidativos avançados (POAs) têm sido apontados como alternativa eficiente para a degradação de poluentes recalcitrantes. Entre os POAs, a fotocatálise utilizando luz solar vem sendo muito estudada tendo em vista sua aplicação no tratamento de efluentes aquosos contendo pesticidas. No presente trabalho, estudou-se a degradação do herbicida amicarbazona (AMZ) por meio do processo TiO2/UV em um reator com coletores parabólicos compostos irradiados por luz solar. Os experimentos foram realizados segundo uma matriz Doehlert para o estudo da influência da concentração inicial de AMZ (20-100 mg L-1), da concentração de catalisador (0,1-1 g L-1) e do número de tubos expostos à luz solar (1-9). Amostras retiradas ao longo do tempo foram analisadas quanto às concentrações de AMZ e de carbono orgânico total (TOC). As medidas radiométricas realizadas indicaram que a radiação UVB-UVA correspondeu em média a ca. 4% da radiação solar total incidente entre 310-2800 nm; a actinometria de ferrioxalato indicou fluxo fotônico médio de 3,58×10-5 mol fótons m-2 s-1 para dias ensolarados típicos. O processo TiO2/UV mostrou-se eficiente para degradação do pesticida, que foi totalmente removido antes de 45 minutos de tratamento, para as seguintes condições: [AMZ]0=21,3 mg L-1; [TiO2]=0,5 g L-1; e 7 tubos. Contudo, nesse caso houve apenas ca. 24% de mineralização e na grande maioria dos casos os valores de TOC permaneceram praticamente constantes, o que indica a formação de sub-produtos recalcitrantes, cuja toxicidade e biodegradabilidade devem ser caracterizadas. A análise estatística dos resultados confirma os efeitos importantes da concentração inicial do pesticida e do número de tubos expostos (volume irradiado), cujo aumento permite compensar a menor incidência de radiação solar. Em alguns experimentos os resultados sugeriram que a degradação da AMZ foi favorecida pela maior concentração de TiO2. Na grande maioria dos casos os valores de ACM foram inferiores a 50 m2 kg-1, o que torna este parâmetro interessante para aumento de escala de processos fotocatalíticos irradiados por luz solar empregados no tratamento de efluentes aquosos contendo amicarbazona. / Advanced oxidative processes (AOP) have been considered as an efficient alternative for the degradation of recalcitrant pollutants. Photocatalysis using solar radiation has been studied for the treatment of wastewaters containing pesticides. In this work, the degradation of the herbicide amicarbazone (AMZ) by the TiO2/UV process was studied in a reactor equipped with compound parabolic collectors irradiated by solar light. The experiments were carried out according to a Doehlert matrix to study the effects AMZ initial concentration (20-100 mg L-1), catalyst concentration (0.1-1 g L-1), and number of tubes exposed to solar light (1-9). Samples were analyzed for AMZ and total organic carbon (TOC) concentrations. Radiometric measurements indicated that UVB-UVA radiation corresponded in average to about 4% of the solar radiation between 310-2800 nm; ferrioxalate actinometry resulted in an average photonic flux of 3.58×10-5 mol fótons m-2 s-1 for typical sunny days. The TiO2/UV process showed to be efficient for the degradation of the pesticide, which was completely removed before 45 minutes of treatment, for the following conditions: [AMZ]0=21.3 mg L-1; [TiO2]=0.5 g L-1; and 7 tubes. However, in this case only ca. 24% of mineralization was achieved, and in most cases TOC values remained practically constant, indicating the formation of recalcitrant by-products whose toxicity and biodegradility should be characterized. Statistical analysis of the results confirmed important effects of pesticide initial concentration and number of tubes exposed (irradiated volume), whose increase enables to compensate the lower incidence of solar radiation. Some experimental results suggested that AMZ degradation was favored by higher TiO2 concentrations. In most cases the values of ACM were lower than 50 m2 kg-1, in such a way that this parameter is interesting for scale-up of solar irradiated photocalytic processes used in the treatment of amicarbazone-containing wastewaters.