This study investigates the degradation of three fluoroquinolone antibiotics by ozone and �OH radicals during ozonation, with identification of the main degradation products. Ozonation was also carried out in a wastewater secondary effluent to study the evolution of these oxidation products. Twenty oxidation products of ciprofloxacin were formed as a result of ozone and/or �OH attack on the quinolone core structure and the piperazinyl substituent. Of those, only twelve oxidation products with intact quinolone moiety were formed upon ozonation in the presence of the radical scavenger t-Butanol. The same holds true for norfloxacin and lomefloxacin due to their similarity of structure with ciprofloxacin. The results indicate that the tertiary amine in the piperazinyl substituent is a preferred target and its oxidation proceeds via the addition of one or two O-atoms to the ring and the cleavage of the ring, while the quinolole moiety tends to have little reactivity towards molecular ozone and its oxidation proceeds by the attack of hydroxyl radical on the carbon-carbon double bond adjacent to the carboxylic acid group. The concentrations of the degradation products behaved non-monotonically as a function of ozone dose and treatment time, yet they exhibited interpretable correlations with changes of the absorbance of effluent organic matter, demonstrating an alternative approach to elucidate the kinetics and mechanisms of the degradation of fluoroquinolones and other antibiotics.

Identification and spectroscopy of degradation products from fluoroquinolone antibiotics in ozonated wastewater

243rd National Meeting (2012)

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