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Research Papers

Influence of Catalyst Properties and Reactor Configuration on the Photocatalytic Degradation of Trichloroethylene Under Sunlight Irradiation

[+] Author and Article Information
Juan M. Coronado1

Environmental Applications of Solar Radiation, CIEMAT, Avenida Complutense 22, Building 42, 28040 Madrid, Spainjuanmanuel.coronado@ciemat.es

Benigno Sánchez, Silvia Suárez, Raquel Portela

Environmental Applications of Solar Radiation, CIEMAT, Avenida Complutense 22, Building 42, 28040 Madrid, Spain

Fernando Fresno1

Solar Concentrating Systems,  CIEMAT, Avenida Complutense 22, Building 42, 28040 Madrid, Spainfernando.fresno@ciemat.es

1

Corresponding authors.

J. Sol. Energy Eng 130(4), 041012 (Oct 06, 2008) (5 pages) doi:10.1115/1.2969797 History: Received November 13, 2007; Revised November 29, 2007; Published October 06, 2008

In this work, the influence of the reactor configuration and the characteristics of the catalysts on the photodegradation of trichloroethylene (TCE) vapors are studied under sunlight illumination. The photocatalytic activity tests were carried out using two types of continuous flow reactors: (i) a compound parabolic collector (CPC) and (ii) a simple flat reactor. Three different photocatalysts based on TiO2 were utilized: (i) commercial powders calcined at 500°C (ii) a TiO2xNx sample synthesized by treating the commercial sample at 500°C in an NH3 gas flow, and (iii) TiO2 thin film coatings on differently shaped borosilicate glass supports prepared by a sol-gel procedure. The obtained data reveal that the photonic efficiency for the removal of TCE is quite high but slightly decreases with increasing the light intensity. The commercial TiO2 sample presents the highest efficiency while nitrogen doping seems to be slightly detrimental for photoactivity, despite the fact that certain photoresponse in the visible can be envisaged. In contrast, transparent sol-gel TiO2 coatings present the highest TCE degradation rate per mass of catalyst. Regarding the type of reactor, it is found that the use of CPCs can be advantageous, especially when dealing with high volumes of effluent and elevated concentration of TCE, although flat reactor also shows a considerable efficiency.

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Copyright © 2008 by American Society of Mechanical Engineers
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Figures

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Figure 1

Scheme of experimental setup used for the photocatalytic activity measurements under sunlight irradiation, showing the configuration of the flat photoreactor

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Figure 2

XRD pattern of the samples: (a) TiO2 Hombikat, (b) TiO2−xNx, and (c) sol-gel TiO2; R and B stand for rutile and brookite reflections, respectively.

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Figure 3

UV-visible spectra of the (a) glass support, (b) sol-gel TiO2 coating measured in transmittance, (c) TiO2 Hombikat, and (d) TiO2−xNx recorded in reflectance

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Figure 4

Variation of the TCE (dotted line) and COCl2 (dashed line) concentration in the flat microreactor using TiO2−xNx as photocatalyst under the following illumination conditions: (a) in the dark, (b) sunlight exposure with an UV-filter, (c) without the filter (irradiance at 365nm1.9–1.8mWcm−2), (d) exposed to diffuse solar radiation with irradiance at 365nm0.04mWcm−2, (e) irradiance at 365nm0.05mWcm−2, and finally (f) in the dark. The thick line shows a fivefold magnification of the COCl2 trace.

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Figure 5

Variation of photonic efficiency with solar irradiance at 365nm for sol-gel TiO2 (squares), TiO2−xNx (circles), and TiO2 Hombikat (triangles) photocatalysts; conditions of the photocatalytic runs: 0.2s residence time, [TCE]0=70ppmv.

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Figure 6

Variation of the amount of TCE degraded per illuminated area with the accumulated incident energy using a CPC reactor with Raschig rings and solar irradiation (solid circles; concentration: 130ppmv of TCE; residence time 2.2s), the flat reactor with Raschig rings and lamps (crossed circles; concentration: 94ppmv of TCE; residence time 2.3s), the flat reactor with a TiO2 Hombikat coated slide exposed to sunlight (solid squares, concentration: 70ppmv of TCE; residence time 0.2s), and artificial light (crossed squares; concentration 70ppmv of TCE; residence time 0.2s)

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