The rate constants of the reactions of O3 with some typical wastewater pollutants (tributyltin, the macrolide antibiotic clarithromycin, the beta blocker metoprolol and the analgesic diclofenac) were determined and some mechanistic aspects were elucidated. Except for tributyltin compounds that react only slowly with O3 (k=4–7 M−1 s−1), the compounds react fast (k>104 M−1 s−1) and can be eliminated at low O3 doses. Clarithromycin reacts at its dimethylamino group and yields the corresponding N-oxide that is no longer biologically active. The nitrogen is also the major site of O3 attack in diclofenac and in metoprolol. This gives rise to •OH radicals and these are the precursors of hydroxylated products and markedly contribute to chloride release in diclofenac.

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