Degradation of acetaminophen in photo-enzyme coupling system with natural organic matters from different sources

Acetaminophen (AAP) is one of the most commonly prescribed over-the-counter drugs with wide distribution in surface water, which has attracted great attention around the world. Photodegradation and enzymatic transformation are important processes for the removal of AAP in water. The influence of natural organic matter (NOM) from different sources on the transformation of AAP by horseradish peroxidase (HRP) in sunlit water was systematically studied. NOM can effectively promote the combined degradation rate of AAP in photo-enzyme coupling system (PECS), and the promotion extents of different NOMs were dependent on their aromaticity and average molecular weights. NOM with low aromaticity and low average molecular weight is more effective. In order to disclose the underlying effects of NOM clearly, the reaction mechanism was clarified through the determination of the photodegradation constant and enzymatic reaction constant. The effect of NOM structure on the photo-enzymatic transformation of AAP was quantified, which showed significant positive correlation with the SUVA₂₅₄ and E₂/E₃ of NOM. Further investigation revealed that the amount of H₂O₂ generated by NOM from different sources was also closely related to SUVA₂₅₄ and E₂/E₃ of NOM. The findings will facilitate understanding the environmental fate of AAP and other pharmaceutical products in natural water.