Kinetic modelling of UV and UV/HO oxidation of an aqueous mixture of antibiotics in a completely mixed batch photoreactor.

The removal kinetics of an aqueous mixture of thirteen antibiotics (i.e., ampicillin, cefuroxime, ciprofloxacin, flumequine, metronidazole, ofloxacin, oxytetracycline, sulfadimethoxine, sulfamethoxazole, sulfamethazine, tetracycline, trimethoprim and tylosin) by batch UV and UV/HO processes has been modeled in this work. First, molar absorption coefficients (ε), direct quantum yields (Φ) and the rate constants of the reaction of antibiotics with hydroxyl radical (k) (model inputs) were determined for each antibiotic and compared with literature data. The values of these parameters range from 0.3 to 21.8 mM cm for ε, < 0.01 to 67.8 mmol·E for Φ and 3.8 × 10 to 1.7 × 10 M s for k. Second, a regression model was developed to compute the rate constants of the reactions of the antibiotics with singlet oxygen (k) from experimental data obtained in batch UV experiments treating a mixture of the antibiotics. k values in the 1-50 × 10 M s range were obtained for the antibiotics studied. Finally, a semi-empirical kinetic model comprising a set of ordinary differential equations was solved to simulate the evolution of the residual concentration of antibiotics and hydrogen peroxide (model outputs) in a completely mixed batch photoreactor. Model predictions were reasonably consistent with the experimental data. The kinetic model developed might be combined with computational fluid dynamics to predict process performance and energy consumption in UV and UV/HO applications at full scale.