Solar photodegradation of pesticides in water by sodium decatungstate

Solar photodecomposition of 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. Titanium dioxide appears to be the most efficient photocatalyst concerning the rate of photodegradation and mineralisation 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 mechanisms of the photodegradation in the presence of the two photocatalysts are discussed. They appear to be different, accounting for the observed difference of reactivity