Enhanced photochemical degradation and transformation of ciprofloxacin in a UV/calcium peroxide system: pH effects, defluorination kinetics, and different components numerical analysis

Abstract

Advanced oxidation processes (AOPs) are highly efficient for the removal of antibiotics from water. The activation of hydrogen peroxide (H2O2) by ultraviolet (UV) has garnered increasing attention. This study describes the enhanced photochemical degradation of emerging contaminants in water using a UV-activated calcium peroxide (UV/CaO2) system, wherein CaO2 can gently produce H2O2 when exposed to UV light. The UV/CaO2 system can expeditiously and efficiently eradicate ciprofloxacin (CIP), in which hydroxyl radicals (•OH) and superoxide anions (O2•-) played critical roles. The superlative rate constant was 0.024 min−1 at an optimal dosage of 0.1 g L−1, which was a 16-fold increase over the rate of pure UV photolysis. The UV/CaO2 system had an excellent defluorination capacity (80% within 60 min). Further, this technology was intensely evaluated over a wide range of pH for the removal of CIP, including H2O2 yields, defluorination rates, as well as correlations with the reactive species generated during the reactions for numerical analysis. The UV/CaO2 system had an excellent anti-interference capacity over a wide pH range. Three major degradation pathways were proposed for the degradation of CIP, together with predictions of the physiological toxicity of these transformation intermediates. This study provides strong technical support for the promotion of this UV/CaO2 water treatment platform, as well as the decontamination and defluorination of water matrixes contaminated with fluoroquinolones.