A B S T R A C TTaking into account that Fenton chemistry can be enhanced under UV radiation, a systematic activation of different H 2 O 2 concentrations (7-50 mM) in 0.05 M Na 2 SO 4 (pH 2 adjusted with H 2 O 4 ) was carried out, in the presence of UV/Fe 2+ in a photochemical reactor. From the experimental results, a simple empirical correlation between the H 2 O 2 activation velocity (AV) and its concentration was derived, as a result, a chemical model for the OH Å production was obtained. Considering that the attractiveness of the Fenton chemistry is its nearstoichiometric generation of a strong oxidant, it is possible to model the oxidation of organic matter under mild conditions. In this way, the fraction of H 2 O 2 produced/consumed provides a measure of the efficiency of the oxidation process. The chemical model was tested in the photochemical reactor with several methylene blue (MB) concentrations (0.1-0.3 mM). Experimentally and theoretically, it was found that 0.1, 0.2, and 0.3 mM MB can be oxidized in 85, 90, and 100 min, respectively. The predictions of the theoretical model are based on 90% of Chemical Oxygen Demand (COD) abatement. Thus, the theoretical results (time for achieving 90% of COD removal, and the stoichiometric amount of H 2 O 2 required for such COD achievement) obtained from the chemical model, agree within a range of 5-15% of relative error against the experimental results. Although Fenton chemistry is very complex, under this approach it is possible to predict the oxidation of the organic matter contained in synthetic industrial effluents by means of a simple chemical model.