The effect of hospital urine components on the degradation of ciprofloxacin during UV/chlorine disinfection process: Kinetics, pathways, and toxicity evaluation

Abstract

UV/chlorine as an advanced oxidation process (AOPs) has been employed to treat contaminants. However, current research has primarily focused on drinking water and sewage treatment. This paper investigated the degradation of ciprofloxacin (CIP) by UV/chlorine treatment in hospital urine components that contain a higher concentration of iodine (I−). The results indicated that the characteristic ions (HCO3−, SO42−, and NH4+) and I− in hospital urine inhibited CIP removal. In contrast, the characteristic ion, Cl− ion promoted this degradation reaction. Surprisingly, microgram levels of I− strongly inhibited CIP degradation. The characteristic ions can reduce the contribution of hydroxyl radicals (HO•) and reactive chlorine species (RCS). I− can decrease the contribution rate of HO• while slightly increasing the contribution of other radical oxidation in phosphate buffer solution (PBS) ascribed to the formation of HOI and reactive iodine species (RIS). Three degradation pathways have been proposed based on the main transformation products: hydroxylation, electron transfer, and halogen substitution. The piperazine ring of CIP was the main reactive group, and the N2, C10, C16, and C13 atoms were identified as reaction sites. Preliminary toxicity analysis suggested that the toxicity of hospital hydrolyzed urine containing iodine was higher than that of PBS.