In this study, an Agilent Technologies 1260 high performance liquid chromatography equipped with diode array detector (HPLC-DAD) was utilized to determine the concentrations of ofloxacin (OFL) and sulfamethoxazole (SMZ) in aqueous solutions in an attempt to understand influencing factors of the photolysis of these two antibiotics in water environment under simulated sunlight and UV light. The initial pH, dissolved oxygen, hydrogen peroxide and dissolved humic acids were evaluated in the study. The photolysis kinetics of OFL and SMZ single component solutions, their simultaneous photo-degradation in the mixed aqueous solutions were explored. Experimental results demonstrated that the photolysis of OFL and SMZ were in line with first order reaction kinetics, and the rate constant of SMZ was larger than that of OFL. Under simulated sunlight, the rates of photolysis were significantly slower than under UV light. The photolysis rates of these two antibiotics were 8.7% and 27.2% lower in mixed solutions, respectively, suggesting a competing mechanism either for photons or for available oxidants. The effects of initial pH on the photo-degradation rates of these two antibiotics were different. As the pH increased, the photolysis rate of OFL first increased and then decreased, the rate was 24.6% at pH 7. With SMZ, the photolysis rate showed a decrease with increasing pH but seemed to increase with alkaline pH, the photolysis rate was 73.7% at pH 7. Hydrogen peroxide (H2O2) and dissolved oxygen as oxidizers tended to enhance the photolysis of OFL and SMZ, while dissolved humic acids at a concentration of 15 mg C/L was showed to inhibit the photolysis of OFL and SMZ.

Photolysis of ofloxacin and sulfamethoxazole

256th National Meeting (2018)

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