No abstract

In this study, titanium dioxide powder obtained by the sol-gel method and TiO2 nanotubes, were prepared. In order to increase the TiO2 photoactivity, the powders and nanotubes obtained were modified by dye sensitization treatment during the oxide synthesis. The sensitizers applied were Quinizarin (Q) and Zinc protoporphyrin (P). The materials synthesized were extensively characterized and it was found that the dye sensitization treatment leads to modify the optical and surface properties of Titania. It was also found that the effectiveness of the dye-sensitized catalysts in the phenol and methyl orange (MO) photodegradation strongly depends on the dye sensitizer employed. Thus, the highest degradation rate for MO was obtained over the conventional Q-TiO2 photocatalyst. In the case of the nanotubes series, the most effective photocatalyst in the MO degradation was based on TiO2-nanotubes sensitized with the dye protoporfirin (ZnP). Selected catalysts were also tested in the phenol and MO photodegradation under visible light and it was observed that these samples are also active under this radiation.

In this study, the treatment of wastewater coming from a river highly polluted with domestic and industrial effluents was evaluated. For this purpose, series of photocatalysts obtained by ZnO and TiO modification were evaluated. The effect of metal addition and Ti precursor (in the case of the titania series) over the physicochemical and photocatalytic properties of the materials obtained was also analyzed. The evaluation of the photocatalytic activity showed that semiconductor modification and precursor used in the materials synthesis are important factors influencing the physicochemical and therefore the photocatalytic properties of the materials obtained. The water samples analyzed in the present work were taken from a highly polluted river, and it was found that the effectiveness of the photocatalytic treatment increases when the reaction time increases and for both, wastewater samples and isolated Escherichia coli strain follow the next order Pt/TiO << ZnO. It was also observed that biochemical and chemical demand oxygen and turbidity significantly decrease after treatment, thus indicating that photocatalysis is a non-selective technology, which can lead to recover wastewater containing different pollutants.

<p>El objetivo de esta investigación fue aislar y caracterizar bacterias solubilizadoras de fosfatos (BSF) asociadas a la rizosfera de <em>Baccharis macrantha </em>y <em>Viburnum triphyllum,</em> y evaluar su capacidad para solubilizar fosfatos en condiciones <em>in vitro</em>. Además se determinó el efecto de la inoculaciónde las cepas de BSF más eficientes sobre el crecimiento de <em>B. macrantha</em>. Las muestras de suelo rizosférico de <em>B. macrantha </em>y <em>V. triphyllum </em>fueron colectadas en los meses de mayo-período de lluvia y septiembre-período seco del 2012. Para la cuantificación de bacterias heterótrofas cultivables y BSF se empleó el método de recuento en placa en los medios Agar Tripticasa de Soya y Pikovskaya (PVK) respectivamente. La capacidad de solubilización de fosfatos de las cepas aisladas se estimó a partir del diámetro de los halos formados alrededor de las colonias en el medio de cultivo PVK después de 7 días de incubación a 28 °C. Los ensayos de inoculación en <em>B. macrantha </em>se realizaron con las BSF más eficientes<em>. </em>La inoculación de las BSF <em>B. firmus y P. fluorescens</em> de forma individual y como inoculante combinado mostro un efecto benéfico, incrementando significativamente el porcentaje de germinación de semillas, la altura de la plántula, la longitud de la raíz y el peso seco de <em>B. macrantha</em>. La inoculación de BSF podría ser considerada una estrategia para mejorar el crecimiento y establecimiento de <em>B. macrantha</em> en pastizales abandonados.</p><p><strong>Growth Promotion of <em>Baccharis macrantha </em>(Asteraceae) by Phosphate Solubilizing Rhizosphere Bacteria</strong>     </p><p>The objectives of this research was to isolate and characterize phosphate solubilizing bacteria (BSF) associated to the rhizosphere of <em>Baccharis macrantha</em> and <em>Viburnum triphyllum</em>, and to assess their ability to solubilize phosphate under conditions in vitro. Furthermore to determine the effect of inoculation of the strains BSF more efficient on the growth of <em>B. macrantha</em>. Rhizosphere soil samples of <em>B. macrantha</em> and <em>V. triphyllum </em>were collected in the months of May-rainy season and September-period dry the 2012. Trypticase Soya Agar and Pikovskaya (PVK) were used for quantification of culturable heterotrophic bacteria and BSF, respectively. The phosphate solubilizing capacity of the isolated strains was estimated from the diameter of the halo around the colonies formed in the culture medium PVK after 7 days incubation at 28 °C. Inoculation assays were performed with more efficient BSF in <em>B. macrantha. </em>Inoculation of BSF <em>Bacillus firmus</em> and <em>Pseudomona fluorescens </em>individually and as inoculant combined showed a beneficial effect, significantly increasing the percentage of seed germination, seedling height, root length and dry weight of <em>B . macrantha</em>. Inoculation the BSF could be considered a strategy to improve the growth and development of <em>B. macrantha</em> in abandoned pastures</p>

In this work, catalysts based on TiO2 modified by fluorination and platinum addition were prepared and evaluated in glycerol oxidation. The materials were characterized by TEM, N2 physisorption, XRD, UV–Vis DRS, XRF and XPS. It was found that fluorination led to an increase in the surface area of TiO2, and by platinization treatment, it was possible to obtain a high absorption in the visible region of the electromagnetic spectrum. From these improved properties, 0.5 wt.% Pt-F-TiO2 was prepared as the best catalyst for the obtention of the highest yield and selectivity towards glyceraldehyde (GAL). It was also observed that the increase in Pt content had a detrimental effect on the effectiveness of fluorinated titania in the glycerol conversion. The fluorination and platinum addition modify some physicochemical properties of TiO2, thus also modifying the reaction mechanism and selectivity during glycerol oxidation.

In this work, fluorinated and platinized TiO2 was evaluated in the glycerol oxidation. Fluorination led to increase the specific surface area of titania, and platinization treatment led to obtain the highest absorption in the visible region of the electromagnetic spectrum; thus, 0.5 wt.% Pt-F-TiO2 was the best catalyst in the obtention of highest yield and selectivity to glyceraldehyde (GAL). It was also found that 2wt.% of Pt content had a detrimental effect in the glycerol conversion. Fluorination and platinum addition led to modify the reaction mechanism and selectivity.