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The photocatalytic performance of TiO 2-SiMgOx ceramic plates for trichloroethylene abatement in gas phase has been evaluated under sun irradiance conditions. A continuous flow Pyrex glass reactor fixed on the focus of a Compound Parabolic Collector has been used. The performance of the hybrid photocatalyst has been evaluated as the variation of the TCE conversion and reaction product formation with the solar irradiance at different total gas flow, TCE concentration, and water vapour content. SiMgOx not only provides adsorbent properties to the photocatalyst, but it also allows the effective use of the material during low solar irradiance conditions. The adsorptiondesorption phenomena play a pivotal role in the behaviour of the system. Thus, TCE conversion curves present two different branches when the sun irradiance increases (sunrise) or decreases (sunset). CO 2 , COCl 2 and DCAC were the most relevant product detected. Meanwhile CO 2 concentration was insensitive to the branch analysed, COCl 2 or DCAC were not indicating the ability of these compound to be adsorbed on the composite. An increase of the UV irradiation at total TCE conversion promotes the CO 2 selectivity. The excess of energy arriving to the reactor favours the direct reaction pathway to produce CO 2. The photonic efficiency, calculated as a function of the rate for CO 2 formation, decreases linearly with the solar irradiance up to around 2 mW cm-2 , where becomes independent. For decontamination systems high TCE conversion is pursuit and then high solar irradiance values are required, in spite of lower photonic efficiency values. The present photocatalyts configuration, with only 17 % of the reactor volume filled with the photoactive material, allows total TCE conversion for 150 ppm and 1 L min-1 in a wide sun irradiance window from 2-4 mW cm-2. The incorporation of water vapour lead to an increase of the CO 2 selectivity keeping the TCE conversion around 90 %, although significant amounts of COCl 2 were observed.

Hybrid photocatalysts based on an adsorbent SiMgOx and a photocatalyst TiO 2 were developed in a plate shape. The ceramic surface was coated with TiO 2 by the slip-casting technique. The effect of the support in the photocatalytic degradation of trichloroethylene (TCE) was analyzed by modifying TiO 2 loading and the layer thickness. Photocatalysts were characterised by N 2 adsorption-desorption, mercury intrusion porosimetry, SEM, UV-vis spectroscopy and XRD. A direct relationship between the TiO 2 content and the photocatalytic activity was observed up to three layers of TiO 2 (0.66 wt.%). Our results indicate that intermediate species generated on the TiO 2 layer can migrate through relatively long distances to react with the OHsurface groups of the support. By increasing the TiO 2 loading of the photocatalyst two effects were observed: trichloroethylene conversion is enhanced, while the efficiency of the oxidation process is decreased at expenses of increasing the selectivity to COCl 2 and dichloroacetylchloride (DCAC). The results are discussed in terms of the layer thickness, TiO 2 amount, TCE conversion and CO 2 , COCl 2 selectivity.

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