O O2 2HO2 2(ads) ˙- ˙
+ O2 ˙ - + e-(cb) → O2 + H2O → HO2 → O2 + H2O ˙ - ˙ 2 → O H - + O H + O 2 ˙ + OH-
(8) (9) (10)
Consequently, when the photocatalyst is irradiated in the presence of O3 a greater number of OH radicals is produced. ˙
EPR studies5, moreover, confirmed that O2 is less electrophylic than O3 on respect to photogenerated electrons onto TiO2 surface.
The above considerations can justify the observed positive effect of photocatalysis coupled with ozonation on the oxidation rate of oxalate anion.6
5. M.D. Hernandez-Alonso, J.J. Coronado, A.J. Maira, J. Soria, V. Loddo, V. Augugliaro, Appl. Catal. B: Environ. 39 (2002) 257 6. M. Addamo, V. Augugliaro, E. García-López, V. Loddo, G. Marcì, L. Palmisano, Catalysis Today, in press (paper presented during the XIX Iberoamerican Symposium of Catalysis).