The present work aims to evaluate the activity of semiconductor oxides (TiO 2 , Nb 2 O 5 and ZnO) supported on NaA and NaY zeolites, as well as their synergistic effect on Reactive Blue Dye (RB250) photodegradation process. Prior to deposition, TiO 2 particles size was reduced by ultrasonic scattering followed by filtration. The particles on the filtrate were used to conduct the experiments. The semiconductors were immobilized in concentrations of 2.5, 5 and 10% (w w -1 ) and the photocatalytic tests were performed at catalyst concentrations of 1 and 2 g L -1 . Moreover, supported catalysts were characterized by XRD, textural analysis, zero point of charge and temperature programmed desorption of NH 3 . A comparison between the supported catalysts showed high activity for the ones supported with ZnO and TiO 2 . Zeolite NaY has broader opened channels than NaA, which reduces the dye molecules blockage, and, as a result, increased the catalyst activity. A higher concentration of supported catalysts (2 g L -1 ) provides greater photocatalytic activity, while higher concentration of semiconductors immobilized on supports does not present significant differences.Efeito sinérgico entre óxidos semicondutores e zeólitas no fotoclareamento do corante têxtil RB250 RESUMO. O objetivo deste trabalho foi avaliar a atividade dos óxidos semicondutores (TiO 2 , Nb 2 O 5 & ZnO) suportados nas zeólitas NaA e NaY e seu efeito sinérgico na fotodegradação do corante têxtil azul reativo (RB250). Antes da deposição, o tamanho das partículas de TiO 2 foi reduzido por dispersão em ultrassom seguido por filtração e foram utilizadas as partículas que passaram através do filtro. Os semicondutores foram imobilizados em concentrações de 2,5, 5 e 10% (m m -1 ) e os testes fotocatalíticos foram realizados em concentrações de catalisador de 1 e 2 g L -1 . Os catalisadores suportados foram caracterizados por DRX, análise textural, ponto de carga zero e dessorção por temperatura programada. Os catalisadores suportados com ZnO e TiO 2 mostraram maior atividade do que o Nb 2 O 5 . Os testes fotocatalíticos indicaram um aumento na atividade dos catalisadores suportados em NaY sendo essa com resultados superiores aos encontrados com a zeólita NaA. Isso por causa dos seus canais mais estreitos que dificultam a entrada de moléculas do corante. A maior concentração de catalisadores suportados (2 g L -1 ) proporciona maior atividade fotocatalítica, enquanto a maior concentração de semicondutores imobilizados em suportes não apresenta diferenças significativas.

Here, the authors (i) discuss the most prominent co‐catalyst for H2 generation structured in the form of Me‐TiO2/MCM‐41 (Me: Ag, Co, Cu, Ni) based on structural, electronic, textural, morphological and optical characterization techniques, such as XRD, wide and small angle, XPS, Fourier‐transform infrared spectroscopy, scanning electron microscopy, B.E.T., textural analysis, photoacoustic spectroscopy and photoluminescence spectroscopy; and (ii) evaluate the difference in hydrogen production in two distinct geometric reactors based on a theoretical study of light distribution inside the reactors supported by the experimental quantum yield calculation. As a result, copper‐doped photocatalyst generated higher hydrogen amount compared to the others. The high photocatalyst performance was due to the greater lamp spectrum absorption, marked by the low bandgap value, and high photoactivity justified by the low rate of electronic recombination. The hydrogen generation in the quartz reactor was seven times higher than the annular one, and when at maximum light power, it is comparable to the most sophisticated reaction systems found in literature. The larger light exposure area per unit volume of the quartz reactor compared to the annular one is the reason why it obtained better results due to the lower emitted photon blockade, with a 1.81% apparent quantum yield.

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Fotodegradação de corante textil azul RB 250 e produção Fotocatalítica de H 2 utilizando TiO 2 Nano suportado em Zeolita ZSM-5 RB 250 blue dye photodegradation and H 2 Photocatalytic production using TiO 2 Nano supported on Zeolite ZSM-5

The photocatalyst composition affects the chemical-physical properties and directly impacts photocatalytic activity, both in the hydrogen production and degradation of organic contaminants. In this work, the influence of zeolitic structures NaA, NaY, and ZSM-5 combined with a 10% active phase, TiO 2 catalyst doped with 1% copper, and cobalt cocatalysts was tested to mineralize the reactive blue dye (CI250) and to produce hydrogen by photocatalysis under ultraviolet radiation. The band gap energy was affected mainly by the cocatalyst, while the Brunauer-Emmett-Teller method (BET) area was affected by the zeolite structure as well as the X-ray diffraction (XRD). The most active catalyst was the Cu@TiO 2 /NaY, which promoted a hydrogen production rate of 240 μmolH 2 gcat À1 using 10% ethanol (v/v) aqueous solution as a sacrificial agent and mineralization of 53% of the organic dye, followed by the catalysts impregnated on ZSM-5 zeolites, which had discolouration up to 50% and hydrogen evolution of 92.6 and 109.7 μmolH 2 gcat À1 for the catalyst doped with Cu and Co, respectively.

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RESUMO -A utilização de fotocatalisadores na degradação de efluentes tem-se demonstrado eficiente devido as suas propriedades oxidativas, sendo necessário, portanto, a seleção de um catalisador adequado, o que inclui a fase ativa e suporte ideais. Assim, o presente trabalho teve como objetivo preparar fotocatalisadores de ZnO e Nb2O5 suportados em zeólita NaA para uso no tratamento de efluente têxtil sintético (solução de corante azul Color Index 250). Os catalisadores foram preparados com 2,5% e 5% (m/m) dos respectivos óxidos e caracterizados por análise textural, difração de raios-X e ponto de carga nulo, características essas que são parâmetros para analise da eficiência dos fotocatalisadores.