On the importance of reactions in the proximity of the gas-water interface: Application to direct ozone reactions of antibiotics in water

A comparison between kinetic models of the direct ozonation in water of a mixture of fifteen antibiotics has been carried out by considering both the reactions in the proximity of gas-water interface (film reactions) and in the water bulk. Stoichiometric coefficients and rate constants of the O3-antibiotic reaction were determined following standard procedures and compared to the values reported in the literature. The importance of stoi-chiometric coefficients in the establishment of the ozone kinetic regimes and kinetic modelling has been dis-cussed. Most of the antibiotics studied react under fast or moderate regime with ozone at the conditions applied. The significance of these reactions in the proximity of gas-water interface is discussed sustained in the appli-cation of film theory. Results have been compared to those obtained from the kinetic approach where ozone reactions in the film are not taken into account. The importance of reactions in the film represents >60% of antibiotics consumption. Deviations between experimental and simulated concentrations of antibiotics are due to the contribution of reaction intermediates to ozone consumption, which is not considered in the kinetic model.