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Deux applications potentielles des reactions photocatalysees par l'anion decatungstate W 10 O 32 4. sous irradiation solaire ont ete explorees. Premierement, nous avons examine les possibilites offertes pour la functionalization des alcanes. Par irradiation en presence de [(tBut) 4 N] 4 W 10 O 32 , le cyclohexane est converti directement en cyclohexanone et en hydroperoxyde, qui produit apres reduction du cyclohexanol. Une petite quantite de produits polyoxygenes est egalement formee. Deuxiemement, nous avons etudie les potentialites d'action de Na 4 W 10 O 32 en tant que photocatalyseur pour la depollution des eaux. Differents phenols et pesticides, dont l'atrazine, ont ete utilises comme substrats et les resultats compares a ceux obtenus en presence de TiO 2 . Ni TiO 2 , ni Na 4 W 10 O 32 ne conduisant a la mineralisation de l'atrazine, nous avons essaye d'integrer photo- et biodegradation dans le but d'obtenir la mineralisation totale du polluant.

Solar photodegradation in aqueous solutions of phenol, 4-chlorophenol, 2,4-dichlorophenol, bromoxynil, atrazine, imidachloprid and oxamyl, in the presence of two photocatalysts titanium dioxide TiO2 and sodium decatungstate Na4W10O32 is reported. TiO2 appears to be the most efficient photocatalyst concerning the rate of photodegradation and mineralization of the pure compounds. However, when the pesticides are used in formulated solutions, the decatungstate anion becomes as efficient or even more efficient than TiO2. The mechanism of the photodegradation in the presence of Na4W10O32 is investigated by nanosecond flash-photolysis experiments, and is compared to the one proposed for TiO2. The difference of reactivity between the two photocatalysts is accounted by the different primary processes of the mechanisms. The formulation effect is investigated with two model surfactants SDS and Triton X100, and 2-chlorophenol as a model pesticide.

In order to analyze a reaction mixture containing pesti - cides and their DPs, it is necessary to ha ve analytical screen - ing methods available that permit separation and identifica- tion of compounds with ve ry diffe rent hy d ro p h i l i c - hydrophobic characteristics and spanning very different con - Abstract. The insecticide Imidacloprid was oxidized in w ater at 50 mg/L under photocatalytic TiO2 in presence of for mulating agents. Analysis of oxidized solutions was performed with both GC-Ion Trap-MS using either EI and CI as ionization modes and LC-Atmospheric Pressure Chemical Ionization (APCI)-MS in order to confirm and evaluate the decay of Imidacloprid and the presence of de gradation products (DPs). LC-APCI-MS techniques allowed the monitoring of Imidacloprid and 6-chloronicotinic acid along the degradation process. GC-MS techniques allowed the detection of f ive DPs, three of which were unequivocally identified. Other complementary techniques such as Total Or ganic Carbon (TOC) and Ion Chromatography (IC) allowed the eval- uation of the mineralization degree achie ved. A tentati ve de gradation pathw ay of Imidacloprid under photocatalysis is proposed . After 450 minutes of ir radiation, none of the DPs or Imidacloprid were detected. Near ly total mineralization was achieved after 700 minutes of ir radiation.