Journal article

Oxidation of antibacterial molecules by aqueous ozone: Moiety-specific reaction kinetics and application to ozone-based wastewater treatment

Ozone and hydroxyl radical (center dot OH) reaction kinetics were measured for 14 antibacterial compounds from nine structural families, to determine whether municipal wastewater ozonation is likely to result in selective oxidation of these compounds' biochemically essential moieties. Each substrate is oxidized by ozone with an apparent second-order rate constant, k(O3,app)' > 1 x 10(3) M-1 s(-1), at pH 7, with the exception of N(4)-acetylsulfamethoxazole (k(O3,app)' is 2.5 x 10(2) M-1 s(-1)) k(O3,app)' values (pH 7) for macrolides, sulfamethoxazole, trimethoprim, tetracycline, vancomycin, and amikacin appear to correspond directly to oxidation of biochemically essential moieties. Initial reactions of ozone with N(4)-acetylsulfamethoxazole, fluoroquinolones, lincomycin, and beta-lactams do not lead to appreciable oxidation of biochemically essential moieties. However, ozone oxidizes these moieties within fluoroquinolones and lincomycin via slower reactions. Measured k(O3,app)' values and second-order center dot OH rate constants, k(center dot OH,app') were utilized to characterize pollutant losses during ozonation of secondary municipal wastewater effluent. These losses were dependent on k(O3,app)', but independent of k(center dot OH,app)". H,app- Ozone doses >= 3 mg/L yielded >= 99% depletion of fast-reacting substrates (k(O3,app)' > 5 x 10(4) M-1 s(-1)) at pH 7.7. Ten substrates reacted predominantly with ozone; only four were oxidized predominantly by center dot OH. These results indicate that many antibacterial compounds will be oxidized in wastewater via moiety-specific reactions with ozone.


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