Mesoporous nanospheres of tungstosilicic acid/titania

JULIÁN A. RENGIFO-HERRERA; ROMINA FRENZEL; EDGARDO L. SOTO,; MIRTA N. BLANCO; LUIS R. PIZZIO

Simposio; Scientific Bases for the Preparation of Heterogeneous Catalysts PREPA11; 2014

The degradation of chemicals present in wastes by photocatalysis is an important issue and its study is a constantlygrowing field. Titanium dioxide has been the most widely used photocatalyst due to its easy availability, lowcost, relatively high chemical stability, and its negligible toxicity. Several factors influence the photocatalytic activityof titania, such as the crystal structure, the crystallinity, the surface area, the porosity, the band gap energy, andthe surface hydroxyl density. Mesoporous titania with suitable properties to be used as photocatalyst was synthesizedvia sol-gel reactions using urea as a low-cost pore-forming agent.The most important disadvantages of titania as photocatalyst are the hole-electron recombination and low surfacearea, which lead to low photocatalytic activity. Therefore, the photocatalytic activity of titania-based catalystscan be improved by separation of electrons and holes, and by increasing the surface area.On the other hand, heteropolyoxometallates (POMs) were employed as effective homogeneous photocatalysts inthe degradation of organic pollutants in water. Furthermore, some heteropolyoxometallates have been used astitania modifiers intending to reduce the charge recombination. They have been added to TiO2 suspensions, incorporatedinto TiO2 colloids, or anchored to TiO2 by chemical interactions. We incorporated TPA into the titania matrixduring the synthesis of TiO2 gel, using urea as low-cost template in order to obtain mesoporous materials. Inaddition, the incorporation of POMs into the titania matrix can improve the density of the catalysts, thus facilitatingtheir separation from heterogeneous reaction systems in order to reuse them.We present here the preparation and characterization of mesoporous titania directly modified with tungstosilicicacid (TSA), using urea as a low-cost pore-forming agent, via HCl-catalyzed sol-gel reactions.The aim is to study the influence of some preparation conditions, such as TSA concentration and calcinationtemperature, on the characteristics of the tungstosilicic acid mesoporous titania nanospheres synthesized via sol?gelreactions and measured the catalytic activity of the materials in the 4-chlorophenol photodegradation.