Influence of suspended natural sands on the photolysis of ciprofloxacin in water

Abstract A comprehensive understanding on the phototransformation of antibiotics in aqueous environments requires consideration of particulate matters contained in natural waters. However, relevant studies on this issue are still limited. Considering the wide distribution of natural sands in natural waters, especially in rainy seasons, the photolysis of CIP in water containing natural sands was investigated, and the influence of natural sands on photolysis was evaluated. The photolytic kinetics showed that the natural sands suspended in water notably accelerated the photodegradation of CIP, and the affecting degree depended on their compositions. The scavenger experiments combined with electron paramagnetic resonance (EPR) experiments showed that 1O2, O2−•, and ·OH generated in the natural sand systems under irradiation, and responsible for the enhanced photodegradation of CIP. The H2O2 and HCl treatment experiments, together with deoxygenation experiments, confirmed that the production of reactive radicals was mainly ascribed to the photoactive oxides and natural organic matter (NOM) in natural sands. The photoproducts of CIP in the presence of natural sands were identified by LC-MS, and the possible degradation pathways were proposed. This study suggested that particulate matters contained in natural waters was a important factor influencing the phototransformation of pollutants, and should be considered in assessing their fate in aqueous environments.