Com o crescimento industrial e urbanização, diversos tipos de poluentes estão sendo encontrados com maior frequência e concentração em corpos hídricos. Um exemplo, são os corantes utilizados pelas indústrias têxteis. Grande parte desses poluentes, não é eliminada pelos processos atuais comumente empregados em estações de tratamento de águas residuais e plantas de tratamento de água potável. Devido a este fato, novas tecnologias para o tratamento da água estão sendo desenvolvidas, como os Processos Oxidativos Avançados (POAs). O objetivo do trabalho foi avaliar os fatores (físicos, químicos e estruturais) de um fotocatalisador (dióxido de titânio - TiO2), bem como as variáveis de um reator fotocatalítico que interferem na fotocatálise heterogênea (um tipo de POA). Para isso, sintetizou-se partindo do TiCl4, compostos de TiO2 com diferentes: morfologias (microesferas e nanotubos), características físicas e químicas, de modo a avaliar suas propriedades fotocatalíticas na degradação de corantes (azul de metileno e rodamina B), comparando os resultados aos obtidos com o nanopó comercial TiO2-P25. O reator fotocatalítico foi construído permitindo variar a potência, o comprimento de onda e a distância das lâmpadas para o sistema de reação. As microesferas sintetizadas a 550° (MT550) e nanotubos de titânia (NTT) apresentaram propriedades fotocatalíticas equivalentes ou superiores às do P25. O reator otimizado operou com quatro lâmpadas UVA próximas. O pH do meio foi determinante nos ensaios de fotocatálise. Sob pH neutro, as microesferas atuaram como adsorventes e fotocatalisadoras da rodamina B e adsorventes do azul de metileno. O P25 apresentou alta capacidade catalítica, em particular para meios neutro e básico. NTT demonstrou alta capacidade de adsorção do azul de metileno, porém baixo rendimento na adsorção e fotocatálise da rodamina B. / With industrial growth and urbanization, several types of pollutants are being found with greater frequency and concentration in water bodies. An example, are the dyes used by the textile industries. Most of these pollutants are not eliminated by current processes commonly used in sewage treatment plants and drinking water treatment plants. Due to this fact, new technologies for water treatment are being developed, such as Advanced Oxidative Processes (POAs). The aim of this work was to evaluate the physical, chemical and structural properties of a photocatalyst (titanium dioxide - TiO2), as well as the variables of a photocatalytic reactor that interfere with heterogeneous photocatalysis (a type of POA). For this, TiO2 compounds with different morphologies (microspheres and nanotubes), physical and chemical characteristics were synthesized from TiCl4, in order to evaluate their photocatalytic properties in the degradation of dyes (methylene blue and rhodamine B), comparing the results obtained with the commercial nanopowder TiO2-P25. The photocatalytic reactor was constructed allowing to vary the power, wavelength and distance of the lamps to the reaction system. The microspheres synthesized at 550°C (MT550) and titania nanotubes (NTT) showed photocatalytic properties similar to or superior to those of P25. The optimized reactor operated with four nearby UVA lamps. The pH of the medium was determinant in the photocatalysis experiments. At neutral pH, the microspheres acted as adsorbents and photocatalysts of rhodamine B and adsorbents of methylene blue. P25 showed high catalytic capacity, in particular for neutral and basic media. NTT showed high adsorption capacity of methylene blue, but low yields in adsorption and photocatalysis of rhodamine B.

Com o crescente número de indústrias pertinentes à área química, atrelada a grande quantidade de novos produtos, grande variedade de resíduos tem sido gerado diariamente. A maior parte do descarte dessas indústrias constitui-se de cargas muito poluentes e de difícil degradação, sendo em muitos casos incinerada. Resíduos desta classe, devido ao poder tóxico, devem como primeira etapa passar por um tratamento químico, visto que o tratamento biológico utiliza bactérias decompositoras as quais não suportariam o meio agressivo. Os processos muito utilizados hoje como tratamento químico são os processos oxidativos avançados (POAs), os quais podem ser utilizados de várias formas diferentes, sendo como caracteristica final a formação de radicais hidroxila. Desta forma, os processos heterogêneos têm recebido muito destaque na descontaminação de águas, principalmente industriais. Desta maneira, o presente trabalho teve como delineamento a construção e aplicação de um reator Counpound Parabolic Concentrator (CPC), para posterior tratamento de água de reação da produção de resina fenólica. Como fonte de radiação utilizada pelo reator, foi utilizada a própria radiação solar com o prematuro intuito de redução de custo do processo. Como fonte de radicais hidroxila, optou-se pelo uso de peróxido de hidrogênio, utilizando como catalisador o dióxido de titânio P25 Degussa. O reator teve como tempo de operação uma hora para cada batelada de 20 litros, onde amostras foram coletadas a cada dez minutos. As condições a serem avaliadas neste projeto, foram definidas de acordo com trabalhos previamente consultados pela literatura. A árvore de dados obtida pós-tratamento foi analisada segundo método de Taguchi utilizando assim uma matriz ortogonal com 16 experimentos, todos eles realizados em duplicata. Como variável resposta do processo foram analisadas a redução de Demanda Química de Oxigênio bem como o Carbono Orgânico Total. Entretanto para as condições dos fatores utilizadas neste trabalho, foi observada uma não redução satisfatória dos paramentros analisados, o que pode ser atribuído ao tempo para cada batelada atrelado a elevada carga orgânica inicial. / With the growing number of industries relevant to the chemical area, linked to large amount of new products, great variety of waste has been generated daily. Most of the disposal of these industries is made up of loads very difficult to clean and degradation, and in many cases burned. Waste from this class, due to the toxic power, as a first step must go through a chemical treatment, since the biological treatment uses decomposing bacteria which can not handle the aggressive media. The processes commonly used today as chemical treatment are advanced oxidation processes (AOPs), which can be used in several different ways, as being characteristic final formation of hydroxyl radicals. Thus, the heterogeneous processes have received much emphasis on clean water, mainly industrial. Thus, this study was to design and implement the construction of a reactor Counpound Parabolic Concentrator (CPC) for further treatment of water from the reaction of phenolic resin production. As a source of radiation used by the reactor itself was used solar radiation with the early effort to reduce the cost of the process. As a source of hydroxyl radicals, we chose to use hydrogen peroxide, using as catalyst titanium dioxide Degussa P25. The reactor had the time of operation an hour for each batch of 20 liters, where samples were collected every ten minutes. The conditions to be evaluated in this project were defined in accordance with those previously found in the literature. The tree of data obtained after treatment was assessed by using Taguchi method as an orthogonal matrix with 16 experiments, all performed in duplicate. As response variable of the process were analyzed to reduce Chemical Oxygen Demand and Total Organic Carbon. However for the conditions of the factors used in this study, we observed no satisfactory reduction of paramentros analyzed, which can be attributed to the time for each batch tied to high organic load stage.

Este trabalho teve como objetivo estudar a fotocatálise heterogênea com Ti'O IND.2' no tratamento de esgoto sanitário secundário, visando a oxidação da matéria orgânica e desinfecção. A luz solar foi utilizada como fonte de radiação. O reator fotocatalítico consistiu de placa de vidro (aproxidamente 0,48 'M POT.2') sobre a qual foi fixado o catalisador (10 g/'M POT.2'). Foi avaliada a influência de parâmetros operacionais (vazão e ângulo de inclinação do fotorreator) na eficiência do processo. As vazões de estudo foram 15; 22,5 e 30 L/h, e os ângulos de inclinação em relação à horizontal foram 2, 12 e 22 graus. Os experimentos foram realizados com dois tipos de efluentes. O primeiro (efluente 1) foi de reator anaeróbio compartimentado tratando esgoto doméstico e o segundo (efluente 2) de reator anaeróbio/aeróbio de leito expandido com meio suporte constituído de carvão ativado que trata o esgoto do Campus I da USP/São Carlos e de contribuições domésticas. Os ensaios foram do tipo batelada com recirculação do esgoto durante 4 horas. Também foi avaliada a fotólise (ensaio apenas com radiação solar) e adsorção do catalisador (ensaio sem luz e com Ti'O IND.2') na oxidação de matéria orgânica e na desinfecção. Foram avaliadas as remoções de matéria orgânica (DQO e COT) e de microrganismos indicadores de contaminação fecal (Clostridium perfringens, coliformes totais, E. coli e colifagos). Os resultados indicaram que a fotocatálise heterogênea foi mais eficiente como método de desinfecção que a fotólise. A resistência dos microrganismos ao processo Ti'O IND.2'/UV, em ordem decrescente, foi: Clostridium perfringens, coliformes totais, E. coli e colifagos. As melhores condições operacionais para inativação de microrganismos no efluente 1 foram: 'alfa' = 2 graus e Q = 22,5 L/h. O ângulo de inclinação da placa teve maior influência na oxidação de COT do efluente 2 do que a vazão. As características físico-químicas dos efluentes tiveram papel importante no resultado final da fotocatálise heterogênea, tanto na oxidação de matéria orgânica como na desinfecção. A concentração inicial de E. coli exerceu maior influência na desinfecção fotocatalítica do que a radiação solar, para as condições dos ensaios realizados. Os reatores de placa plana com Ti'O IND.2' imobilizado, quando expostos à luz solar, devem ser vedados para evitar evaporação excessiva / The heterogeneous photocatalysis with Ti'O IND.2' and solar radiation in secondary wastewater treatment to remove organic matter and microorganisms was investigated. A glass plate (approximate 0.48 'M POT.2') with immobilized titanium dioxide (10 g/'M POT.2') was operated in different flow rates (15; 22.5 and 30 L/h) and angles in relation to horizontal (2, 12 and 22 degrees). Two effluents were used in the assays. The first (effluent 1) was from an anaerobic reactor treating sewage and the second (effluent 2) from an anaerobic/aerobic granular activated carbon expanded bed reactor which receives the wastewater collected in the Campus of USP/São Carlos and from the surrounding neighborhood of the campus. The assays were carried out in batch with recirculation time of 4 hours. The photolysis (only solar radiation) and the catalyst adsorption (Ti'O IND.2' in the dark) in organic matter removal and disinfection were evaluated. The oxidation of organic matter (COD and TOC) and inactivation of indicators of fecal contamination (Clostridium perfringens, total coliforms, E. coli, and coliphages) were evaluated. The results shows that heterogeneous photocatalysis was more efficient in effluents disinfection than the photolysis. The resistance of the microorganisms to Ti'O IND.2'/UV process was in decreasing order: Clostridium perfringens, total coliforms, E. coli and coliphages. The best operational conditions for microorganisms inactivation in effluent 1 are: 'alfa' = 2 degrees and Q = 22.5 L/h. TOC oxidation in effluent 2 was more influenced by angle than by flow rate. The physical and chemical characteristics of the effluents had an important role in oxidation and disinfection. Initial E. coli concentration was more important than intensity of solar radiation during photocatalytic disinfection in the experimental conditions of this work. The reactors with immobilized Ti'O IND.2' open to solar radiation have to be closed to avoid excessive evaporation

Com o crescente número de indústrias pertinentes à área química, atrelada a grande quantidade de novos produtos, grande variedade de resíduos tem sido gerado diariamente. A maior parte do descarte dessas indústrias constitui-se de cargas muito poluentes e de difícil degradação, sendo em muitos casos incinerada. Resíduos desta classe, devido ao poder tóxico, devem como primeira etapa passar por um tratamento químico, visto que o tratamento biológico utiliza bactérias decompositoras as quais não suportariam o meio agressivo. Os processos muito utilizados hoje como tratamento químico são os processos oxidativos avançados (POAs), os quais podem ser utilizados de várias formas diferentes, sendo como caracteristica final a formação de radicais hidroxila. Desta forma, os processos heterogêneos têm recebido muito destaque na descontaminação de águas, principalmente industriais. Desta maneira, o presente trabalho teve como delineamento a construção e aplicação de um reator Counpound Parabolic Concentrator (CPC), para posterior tratamento de água de reação da produção de resina fenólica. Como fonte de radiação utilizada pelo reator, foi utilizada a própria radiação solar com o prematuro intuito de redução de custo do processo. Como fonte de radicais hidroxila, optou-se pelo uso de peróxido de hidrogênio, utilizando como catalisador o dióxido de titânio P25 Degussa. O reator teve como tempo de operação uma hora para cada batelada de 20 litros, onde amostras foram coletadas a cada dez minutos. As condições a serem avaliadas neste projeto, foram definidas de acordo com trabalhos previamente consultados pela literatura. A árvore de dados obtida pós-tratamento foi analisada segundo método de Taguchi utilizando assim uma matriz ortogonal com 16 experimentos, todos eles realizados em duplicata. Como variável resposta do processo foram analisadas a redução de Demanda Química de Oxigênio bem como o Carbono Orgânico Total. Entretanto para as condições dos fatores utilizadas neste trabalho, foi observada uma não redução satisfatória dos paramentros analisados, o que pode ser atribuído ao tempo para cada batelada atrelado a elevada carga orgânica inicial. / With the growing number of industries relevant to the chemical area, linked to large amount of new products, great variety of waste has been generated daily. Most of the disposal of these industries is made up of loads very difficult to clean and degradation, and in many cases burned. Waste from this class, due to the toxic power, as a first step must go through a chemical treatment, since the biological treatment uses decomposing bacteria which can not handle the aggressive media. The processes commonly used today as chemical treatment are advanced oxidation processes (AOPs), which can be used in several different ways, as being characteristic final formation of hydroxyl radicals. Thus, the heterogeneous processes have received much emphasis on clean water, mainly industrial. Thus, this study was to design and implement the construction of a reactor Counpound Parabolic Concentrator (CPC) for further treatment of water from the reaction of phenolic resin production. As a source of radiation used by the reactor itself was used solar radiation with the early effort to reduce the cost of the process. As a source of hydroxyl radicals, we chose to use hydrogen peroxide, using as catalyst titanium dioxide Degussa P25. The reactor had the time of operation an hour for each batch of 20 liters, where samples were collected every ten minutes. The conditions to be evaluated in this project were defined in accordance with those previously found in the literature. The tree of data obtained after treatment was assessed by using Taguchi method as an orthogonal matrix with 16 experiments, all performed in duplicate. As response variable of the process were analyzed to reduce Chemical Oxygen Demand and Total Organic Carbon. However for the conditions of the factors used in this study, we observed no satisfactory reduction of paramentros analyzed, which can be attributed to the time for each batch tied to high organic load stage.

No description available.

1-butyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide ([BMIM]Tf2N) was investigated as a multifunctional solvent, ligand, and reducing agent for platinum deposition onto well-defined CdSe@CdS nanorods. Platinum deposition was carried out thermally and photochemically using Pt(acac)2 as the metal precursor. Thermal deposition was investigated in [BMIM]Tf2N with and without addition of a sacrificial reducing agent, and product topology was compared with the products obtained from polyol reduction using 1,2-hexadecanediol, oleic acid, and oleylamine in diphenyl ether. Photochemically induced platinum deposition was carried out at room temperature in [BMIM]Tf2N, and product topology was compared with the photodeposition products obtained from a toluene dispersion. Thermal deposition of platinum in ionic liquid showed rods of broken morphology and small platinum nanoparticles speckled across the rods’ surface, while photodeposition of platinum exhibited particles decorated throughout the nanorod surface but larger in size than those exhibited by thermal means. Photocatalytic reduction of methylene blue was studied using these Pt-CdSe@CdS heterostructured nanoparticles, and catalytic performance was correlated with topology and synthetic history. Initial findings of catalytic performance suggest that there in an advantage of depositing platinum nanoparticles onto the CdSe@CdS in the ionic liquid system. Methylene blue dye was degraded using each system and the results show and there is an increased performance of the nanorods synthesized in the ionic system.

Titanium dioxide(TiO2) is a stable, effective and well-known photocatalyst for degradation of pollutants. However, its practical applications are limited due to the need for energy higher than 3.2 eV, or a wavelength lower than 390 nm (high frequency waves, ultraviolet and above) hindering its ability to effectively work in the visible light region (about 400 nm to 700 nm). Nitrogen-doped TiO2 (N-TiO2) has garnered some attention as a photocatalyst as it appears to work even in the visible light region. This could allow the utilization of a larger part of the solar spectrum. This thesis presents the results of photocatalytic degradation of methylene blue (MB) carried out under simulated visible light by using TiO2 and N-TiO2(doped in the lab) to evaluate and compare their efficiencies under similar conditions.

Maintaining a constant supply of clean drinking water is among the most pressing global challenges in our time. About one-third of the population is affected by the water scarcity and it can only get worse with climate change, rapid industrialization, and the population growth. Even though nearly 70 percent of the planet is covered by water, the consumable freshwater content is only 2.5 percent of it. Unfortunately, the accessible portion of it is only 1 percent. Even so, most of the freshwater bodies are choked with pollution. Considering the vast availability of saline water on the planet and the increasing wastewater generation, seawater desalination, and wastewater treatment and recycling seem to have the potential to address current water-related issues. Therefore, it is necessary to find efficient techniques for seawater desalination and wastewater treatment. The use of nanostructured materials for these applications is becoming a popular approach due to the unique chemical and physical properties they possess compared to bulk materials Solar energy is the cleanest and most abundant renewable natural resource available. Materials for solar photothermal energy conversion are highly sought after for their cost savings, clean environment, and broad utility in providing water heating and/or steam for many applications including domestic water heating and solar-driven desalination. Extensive research efforts have been made to develop efficient solar absorbers with characteristics such as low weight, low thermal conductivity, broad solar absorption and porosity to be able to float on water to provide more efficient and cost-effective solar steam generation systems. Metal NPs have been proposed to take advantage of the high efficiency of the photothermal energy conversion associated with surface plasmon resonance absorption. Nanostructured carbon-based materials such as graphene oxide, carbon nanotubes, carbonized biomass are also in use due to their excellent photothermal energy conversion ability over the range of the visible and near infra-red region of the electromagnetic spectrum. In this dissertation, five projects based on the utility of nanostructured materials for desalination, photocatalysis and water treatment will be discussed. The first three projects involve the fabrication and design of plasmonic and carbon-based photothermal materials for applications in solar steam generation, water desalination, and wastewater treatment. In the fourth project, a unique shape of ZnO nanostructure was synthesized for photodegradation of organic dyes in industrial wastewater. The final project demonstrates the shape-controlled synthesis of iron carbide nanostructures and composite materials of aminated graphene oxide for the removal of Cr(VI) from wastewater.

Dans une société qui peine à renoncer à l'utilisation des énergies fossiles, la production d'hydrogène à partir d'eau par photocatalyse solaire est une alternative que les chimistes se doivent d'explorer. La mise en place de cette solution est conditionnée à la résolution de deux problèmes majeurs : augmenter l'efficacité de la conversion solaire par le développement de nouveaux semi-conducteurs, et améliorer la réactivité en surface par le développement de co-catalyseurs efficaces. Dans un premier temps, nous avons contribué à l'étude d'une nouvelle famille de semi-conducteurs par des calculs ab initio DFT. Différentes propriétés clés ont été calculées et comparées aux valeurs expérimentales. Nous avons montré que pour une même famille de matériaux, l'absorption peut être contrôlée par modification de la composition.Ensuite, nous nous sommes focalisés sur la réaction d'oxydation de l'eau (OER). Pour cette réaction les catalyseurs de type oxyhydroxydes et leurs dérivés sont très prometteurs car à la fois efficaces et contenant des éléments abondants sur Terre, mais la compréhension de son mécanisme reste limitée. Sur le composé modèle CoOOH, nous en avons réalisé une analyse approfondie par une étude exhaustive des intermédiaires ainsi que par modélisation explicite du potentiel électrochimique. Nos études ont montré la nécessite de prendre en compte plusieurs sites réactionnels dans la détermination des mécanismes d'oxydation de l'eau sur la surface de ces catalyseurs. Enfin, une étude préliminaire de l'utilisation de la biomasse a été menée, dans le but de combiner valorisation de la biomasse et production d'hydrogène. Le cas de l'oxydation du glycérol est envisagé. / In a society struggling to waive the use of fossil fuels, hydrogen production from water by solar photocatalysis is a alternative chemists have to consider. Setting up of this solutions asks to tackle two major issues : increase solar energy conversion by developing new semiconductors, and enhance the surface reactivity by developing efficient cocatalysts.First, DFT \emph{ab initio} calculations were carried out on a new family of semiconductor materials. Different key properties were computed and compared to experimental values. We showed that for a same material family, absorption can be controlled by changing the composition.Then, we focused on Oxygen Evolution Reaction (OER). For this reaction oxyhydroxides catalysts and their derivatives seem promising as both efficient and containing earth-abundant elements, but the understanding of its mechanism still remains unclear. On CoOOH model compound, we realised an extended analysis by a comprehensive study of intermediates and by explicit modelling of electrochemical potential. Our studies showed that taking into account several reactive sites is necessary to determine the OER mechanism on these catalysts' surface.Last, a preliminary study of biomass use was carried, in order to combine its valorization along with hydrogen production. The case of glycerol photoreforming is considered.

The crisis of freshwater has been a big concern worldwide. Water contamination that occurs through the discharge of toxic pollutants from different natural and anthropogenic sources have worsened the situation. Adsorption has emerged as a simple and economical water treatment procedure although the challenge is to find the right adsorbent that can efficiently remove the target contaminant followed by their easy recovery from the reaction vessel. In this dissertation, I have focused on the synthesis, characterizations and applications of environmentally compatible and magnetic humic acid coated magnetite nanoparticles (HA-MNP) as a potential adsorbent for water purification. Phosphate is an essential nutrient for many plants and organisms in the environment. However, it can also cause water pollution when present in excess amounts. The adsorption experiments showed that the laboratory synthesized nanoparticles (HA-MNP) can remove more than 90% of phosphate from water mainly through the mechanism of chemisorption. The overall removal process is spontaneous, endothermic and favorable. Water contamination by arsenic is considered one of the biggest natural disasters in human history. In the study, HA-MNP has been applied for the successful trapping and separation of two highly toxic inorganic As species, As(III) and As(V) from water. The removal of As(V) was faster than As(III) for the same initial arsenic concentration and HA-MNP loading. The binding of As species is mainly attributed to three different phases, rapid surface association, intraparticle diffusion and equilibrium adsorption. Selenium is a micronutrient for humans that can be toxic at modest concentrations. The remediation of toxic selenium species, Se(IV) and Se(VI) by using HA-MNP has been found effective under a variety of environmental conditions except at highly alkaline pH and the presence of sulfate and phosphate in aqueous solution. Selenite or Se(IV) forms strong inner sphere complexes while Se(VI) forms relatively weaker outer sphere complexes with the adsorbent sites. The oxidation and adsorption of As(III) is explored by using the photocatalytic and adsorptive behavior of HA-MNP. The higher removal efficiency is attained through the reactive oxygen species mediated photo-conversion As(III) to As(V). Combination of oxygen and 350 nm light provides the best results.