Hugo Alfonso Rojas Sarmiento

Urban wastewater treatment by using Ag/ZnO and Pt/TiO2 photocatalysts

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 TiO2 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/TiO2 << 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.

Hidrogenación de p-nitrofenol mediante el uso de catalizadores de Ir, Ni e Ir-Ni soportados en TiO2

Los catalizadores de Ir/TiO2,Ni/TiO2 e Ir-Ni/TiO2 fueron obtenidos mediante impregnacion humeda, a una concentracion de 1% en peso del metal. Los catalizadores resultantes se caracterizaron mediante analisis de difraccion de rayos X (DRX), fisisorcion con nitrogeno a 77K, quimisorcion de hidrogeno y temperatura programada de reduccion (TPR). Los solidos sintetizados fueron empleados como catalizadores en la reaccion de hidrogenacion de pnitrofenol para la obtencion de p-aminofenol, importante intermediario para la sintesis de diversos analgesicos y antipireticos. Los ensayos cataliticos se llevaron a cabo en un reactor tipo Batch a 0,62 MPa, 363K y etanol como disolvente. El progreso de la reaccion fuemonitoreado por cromatografia de gases. El catalizador Ir/TiO2 exhibio el mayor nivel de conversion de p-nitrofenol (95,6% en 9 horas de reaccion), lo cual fue atribuido a la presencia de sitios activos originados por el iridio y al efecto SMSI (interaccion fuertemetal soporte) por parte del iridio y niquel.Todos los catalizadores exhibieron una selectividad hacia el p- aminofenol del 100%.

Hidrogenación de Furfural sobre Catalizadores Ir/TiO2. Efecto de la Temperatura de Reducción

Furfuryl alcohol is used inLysine and Vitamin C synthesis, this is obtained by furfural hydrogenation, for this reaction is used as, catalyst Cu-Cr, but this high toxicity has increased interest in studying catalytic systems to lessen the environmental impact [1]. In this research were studied catalysts Ir/TiO 2 , reduced at temperatures between 473 K and 773 K, finding the largest 773 K conversion, selectivity was furfuryl alcohol increases at higher temperature reduction, while at lower temperature is favored formation acetals due to acid sites on the catalysts. We found the presence of SMSI effect at high temperatures, as ascertained by chemisorption. The results of XPS realize the strong influence of the SMSI on the catalytic activity. Analyses by TPR showed the presence of acid sites on the catalysts which explains the changes in selectivity, due to the release of species from the pioneering metal used for the preparation of the catalysts.