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Previous issue date: 2016-05-16 === Coordena??o de Aperfei?oamento de Pessoal de N?vel Superior (CAPES) === Um dos materiais que atualmente est? em destaque s?o os compostos de ni?bio, por apresentarem caracter?sticas como acidez, propriedades oxidativas e fotocatal?ticas e por ser um dos metais mais abundantes do pa?s, sendo o Brasil o maior produtor mundial. Este trabalho avaliou a efici?ncia da fotocat?lise heterog?nea de materiais de ni?bio na oxida??o de metanol e na inativa??o do microrganismo Escherichia Coli. Foram sintetizados catalisadores a base de ni?bio Nb2O5 e foram feitas imobiliza??es (coating) utilizando ?xido de ni?bio. Diante das caracteriza??es, foi poss?vel verificar a forma??o de esp?cies de ?xido de ni?bio e niobatos de s?dio dependendo da metodologia de s?ntese adotada. Esses materiais foram avaliados na oxida??o de metanol em diferentes concentra??es de catalisadores e apresentaram uma efici?ncia na forma??o do formalde?do proveniente da oxida??o, esta efici?ncia est? diretamente relacionada com a concentra??o dos catalisadores, sendo o material de niobato de s?dio o que apresentou maior efici?ncia, devido as suas propriedades texturais, ?pticas, sendo este um material promissor no ramo da fotocat?lise. Para os sistemas de imobiliza??o (coating), verificou-se que o revestimento ideal ? obtido com tr?s imobiliza??es, estes materiais foram analisados na oxida??o de metanol e na inativa??o de microrganismo Escherichia Coli. Estes sistemas (coating) mostram uma boa atividade na oxida??o de metanol, apesar de apresentar resultados inferiores quando comparados aos materiais em suspens?o de ?xido de ni?bio, por?m a grande vantagem dos sistemas imobilizados em rela??o ao de suspens?es s?o a sua reutiliza??o. Em rela??o ? inativa??o da Escherichia Coli, foi verificado que os sistemas imobilizados n?o s?o muitos ativos e que o microrganismo ? bastante dependendo do meio em que se encontra. === One of the materials that is currently highlighted are the compounds of
niobium, because they have features like acidity, oxidative and photocatalytic
properties and for being one of the most abundant metals in the country, Brazil
is the world's largest producer. In this scenario, the work has to evaluate the
efficiency of heterogeneous photocatalysis niobium materials in the oxidation of
methanol and the inactivation of Escherichia coli using immobilization systems
?coating? and suspension. Commercial niobium oxide (Nb2O5) was evaluated in
suspension and immobilization in different systems (tubes and rings) for
photocatalytic processes for water treatment (methanol oxidation and
inactivation of Escherichia coli). From the results of the commercial Nb2O5
characterizations was observed the presence of an amorphous structure with
heat thermal treatment at temperatures above 550 ?C becomes crystalline
phases, however, this fact produce a significant aggregation of the particles
which reduced the specific area and the photocatalytic activity. The not
calcined Nb2O5 material showed a higher activity, for both oxidation of methanol
as for the inactivation of bacterial tests, the latter being very sensitive to the
chemical composition water. Immobilization of the photocatalyst reactor walls
prevents the need for removal of Nb2O5 particles after treatment, but
significantly reduction its activity. In contrast, immobilization in a fixed-bed
(rings) led to a moderate reduction in activity, which is counteracted by
improvement in the long-term stability of the material. Niobium catalysts were
synthesized using a refluxing method with and without the use of NaOH in
different conditions of synthesis and characterized by different techniques in
order to verify the phase formation of niobium. From the results of X-ray
diffraction for the synthesized materials were recorded forming of species
niobium oxide and sodium niobates depending on the adopted synthesis
methodology. The catalytic activity of these materials was evaluated in the
oxidation of methanol in relation to the amount of catalyst in which the activities
have different behaviors have been dependent on the structure, surface and
morphological parameters. Materials with sodium niobate structure have a lineal
tendency of activity in relation to the mass of catalysts, while the materials
niobium oxide structure have an abrupt loss of their catalytic activity at higher
catalyst concentrations, indicating that the dispersion of the light is higher in
these catalysts as increases the amount of particles in suspension. Among the
materials synthesized and analyzed in the oxidation of methanol, which was
more efficient, was the material of sodium niobate NaNbO3 to their textural
properties, optical, which is a promising material for photocatalysis.
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