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AQUACAT Résumé de rapport

Project ID: ICA3-CT-2002-10016
Financé au titre de: FP5-INCO 2
Pays: France

Photocatalytic activity of TiO2 Ahlstrom papers for the degradation of organic pollutants

To avoid the final tedious filtration of titania photocatalyst when used in slurry and which makes the whole system unrealistic and absoluty not adaptable and transferable to developing countries, we had to deposit the solid on a flexible, photo-inert support: the AHLSTROM paper prepared by J. DUSSAUD (partner n°8) which could be inserted on both types of supports (fin and coaxial) inside the final AQUACAT prototype. The photocatalytic activity of the resulting solid was tested in different reactions of degradation of pollutants: chemicals (phenol), pesticide (diuron, imazapyr), dyes (Congored, Remazol Black 5 , Reactive Red 2). All these pollutants could be successfully totally degraded. In parallel, it was checked that the AQUACAT prototype was efficiently designed: proportionality of the reaction rate with (i) the radiant flux; (ii)the initial concentration and (iii) the mass of catalyst employed directly linked to the number of tubings used.

The initial paper underwent some titania leakage. This was remediated by a new preparation of paper-supported titania with less photocatalyst and an increase in the silica binder.

The conclusions are that the AQUACAT prototype using supported titania is working in optimal conditions for a given solar radiant flux. The reaction rate was found to be independent of the flow rate. This makes possible the use of a low flow rate (2 L/min).

The positive consequences of using low flow rates are the following:
(1) preservation of the deposited catalyst from abrasion and leaching of titania from it support.
(2) use of a low electrical power provided by the photovoltaic panels for the recirculating pump.
(3) conservation of purified (drinkable) water in clean conditions (no recontamination).
(4) conservation of the pump in constant steady state working conditions.
(5) maintenance of the photocatalytic bed and of the tubings and reservoir of the whole prototype in clean conditions between two successive runs (prevention of the development of biofilms, of fungi, algae, ... detected during the storage of the prototype on the catalyst in contact with humid air).

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