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Research Papers

Solar Photocatalysis for the Elimination of Trichloroethylene in the Gas Phase

[+] Author and Article Information
Juan M. Coronado

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

Benigno Sánchez, Raquel Portela, Silvia Suárez

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

J. Sol. Energy Eng 130(1), 011016 (Dec 28, 2007) (4 pages) doi:10.1115/1.2807194 History: Received October 06, 2006; Revised May 25, 2007; Published December 28, 2007

In the present work, we have studied the photocatalytic degradation of trichloroethylene (TCE) under sunlight illumination with the aim of determining the feasibility of using this technology for gas purification. For these experiments, a continuous flow reactor was employed. This system is basically constituted by a Pyrex glass tube located in the focus of a compound parabolic collector made of anodized aluminum. Raschig rings of borosilicate glass coated with TiO2 and randomly packed within the reactor tube were used as photocatalyts. Results obtained using sunlight illumination indicate that this continuous flow solar reactor can achieve complete TCE degradation. Experimentally, it is found that for moderate conversions, the TCE degradation rate increases linearly with solar irradiance, but a dependence of lower order is observed when removal of the pollutant is almost complete. On the other hand, photonic efficiency decreases linearly with solar irradiance, and it is higher when the molar flow fed to the photoreactor increases. In contrast, the selectivity toward the different partial degradation products (dichloroacetyl chloride, COCl2, etc.) is basically insensitive to solar irradiance.

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Figures

Grahic Jump Location
Figure 1

(A) Picture of the solar photoreactor showing the two CPC units, one with the borosilicate glass tube empty and the other partly filled with the TiO2 coated Raschig rings. (B) Scheme of the gas circulation in the system: by switching the four-way valve, the stream can be driven either to the empty tube or through both of them.

Grahic Jump Location
Figure 2

Variation in TCE conversion using the solar reactor (residence time of 2.3s, TCE concentration of 590ppmv) and solar irradiance at 365nm as a function of the irradiation time. Dashed areas show the results obtained when the gas stream flows through the empty tube.

Grahic Jump Location
Figure 3

Variation of amount of TCE eliminated per illuminated area versus the accumulated incident sunlight energy at 365nm under two different operation conditions: solid squares, concentration of 450ppmv of TCE, residence time of 0.9s; crossed circles, concentration of 430ppmv of TCE and residence time of 2.3s.

Grahic Jump Location
Figure 4

Variation of TCE conversion with the solar irradiance at 365nm at 1.9s (circles) and 1.4s (squares) of residence time and for initial concentrations of 650ppmv (squares) and 605ppmv (circles). Dashed lines represent the least squares fitting to the variation of the conversion with the square root of the solar irradiance (see text for details).

Grahic Jump Location
Figure 5

Photonic efficiency (ξ) for TCE degradation as a function of solar irradiance at 365nm obtained at the following conditions: 1.4s residence time, [TCE]=650ppmv (blue triangles); 1.9s residence time, [TCE]=605ppmv (red circles); 2.3s residence time, [TCE]=430ppmv (black squares); and 2.2s residence time, [TCE]=130ppmv (pink rhombs).

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