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Highlights  Investigation of process conditions for the degradation of sulfamethoxazole  Identification of degradation products for elucidation of the degradation mechanism  Elucidation of pH influence on formation of degradation products

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In this study, the degradation of ciprofloxacin (CIP) in wastewater was investigated using UVbased sulfate radical advanced oxidation processes (SR-AOP) and UV-based advanced reduction processes (ARP). More specifically, a comparison of the UV-based persulfate advanced oxidation process (the UV/PS process) and the UV-based sulfite advanced reduction process (the UV/sulfite process) was made. As for the UV-based SR-AOPs, the UV/PS process was much more efficient than the UV-based peroxymonosulfate advanced oxidation process (the UV/PMS process), with pseudo first order reaction rate constants (kobs) of 0.752 and 0.145 min -1 , respectively. For the UV-based ARPs, the UV/sulfite process was the most efficient, compared to the UV/sulfide and the UV/dithionite process (kobs of 0.269, 0.0157 and 0.0329 min -1 , respectively). The optimal process parameters for both the UV/PS and the UV/sulfite process were determined and the contribution of the produced reactive species were identified.For the UV/PS process, maximal CIP degradation was found at pH 8, and both •OH and •SO4were responsible for CIP degradation. For the UV/sulfite process, •H and •eaqwere responsible for CIP degradation, with •eaqbeing the predominant radical at pH 8.5. Although CIP degradation was much faster for the UV/PS process, the UV/sulfite process was determined to be much more efficient in the defluorination of CIP.

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