Programme  Poster session 4  abstract 221

Photocatalytic Reaction Engineering for Solar Water Detoxification.

Author(s): Vincent Goetz, Jean-Pierre Cambon, Daniel Sacco, Gael Plantard
PROMES-CNRS UPR 8521 Process Materials ans Solar Energy Laboratory), Tecnosud, Rambla de la Thermodynamique, 66100 Perpignan, France.

Keyword(s): Chemical Engineering, Heterogeneous photocatalysis, water detoxification, atrazine

Article: abs221_article.pdf
Poster: abs221_poster.pdf
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Session: Poster session 4
AbstractHeterogeneous photocatalysis is

an alternative method for the removal of organic pollutants in water. The photo excitation of a semi-conductor under

ultra violet (UV) irradiation entails the production of hydroxyl radicals, one of the most oxidative chemical species.

Combined with solar energy this process of water detoxification is in perfect agreement with the requirement of

sustainable processes development. In the open literature, papers have already demonstrated the practical ability of

photocatalysis method for the degradation of biorecalcitrant pesticides and more particularly atrazine. This pollutant

is sometimes found in drinking water and has noxious consequences on man’s environment. With the global objective

to design large scale solar water treatment plants, a necessary initial step is the development of a reliable

photocatalytic reactor model. The photocatalytic semi-conductor used is supported TiO2 on cellulose based paper

(Alhstrom Grade 1048®) placed in a tubular reactor irradiated thanks to an UV source in the range of solar UV

irradiation powers. In a first part, data acquisition on the kinetic of atrazine degradation was made with an

experimental laboratory plant. Evolutions of the concentration of atrazine as a function of the time were measured in

a closed fluid loop connecting the tubular reactor and a vessel of atrazine. Experiments were performed for a large

range of UV powers, initial concentrations of pollutant and hydrodynamic flowing modes in the tubular reactor. From

these results an original model was developed. It is based on the coupling between: mass transfer from the liquid

phase to the surface of the catalyst; adsorption of the pollutant molecules by TiO2; photocatalytic reaction rate.

Comparisons between the simulated values of the concentration as a function of time and the experimental ones

validate the proposed mechanisms. It is shown that in the range of experimental conditions explored, the apparent

global kinetic basically depends from the combination of two limiting phenomena: the mass transfer in the liquid phase

and the intrinsic photocatalytic rate. Relative importance of these two limitations is discussed and depends on the

hydrodynamic flowing mode (laminar or turbulent) and the level of the irradiation flux. The validated model is a tool

readily usable for reactor design and scale-up.

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