Predicting pharmaceutical degradation by UV (MP)/H2O2 processes: A kinetic model

• (Photo)kinetic model of polychromatic (MP) UV advanced oxidation processes.
• Degradation pathways via direct photolysis, OH radical reactions and carbonate radical reactions.
• Validation of model with large group of pharmaceuticals.
• Validation of model in different water matrices.
• Sensitivity analysis for the chemical reactions involved, including nitrate reactions.

A kinetic model for the degradation of organic micropollutants (OMPs) by MP UV lamps has been developed. The model includes (photo)chemical reactions of hydrogen peroxide and nitrate; reactions with the most important water matrix components; changes in pH; and transient radical concentrations. Three pathways of organic micropollutant degradation are involved: direct photolysis, hydroxyl radical reactions and carbonate radical reactions. The model was validated using collimated beam experiments for a group of 35 pharmaceuticals in synthetic and natural water matrices. For MP UV with 10 mg/L H2O2, good agreement between the modelled and measured degradation rates was found. For MP UV without H2O2, most of the pharmaceuticals were well predicted, except for the sulphonamides. A sensitivity analysis on different water matrix constituents was performed for MP UV with H2O2, NO3- and both H2O2 and NO3-. Also, the most important chemical reactions for the degradation of OMPs are identified for different water matrices.