Removal of ciprofloxacin from water by nitrogen doped TiO2 immobilized on glass spheres: Rapid screening of degradation products

Abstract

Nitrogen doped TiO2 (N-TiO2) powders with different nitrogen doping dosages (urea) were prepared by sol gel method. Then, the powders were immobilized on the glass spheres by sodium silicate to improve its recyclability. The structure and morphological properties also were characterized. A common antibiotic ciprofloxacin (CIP) as water pollutant, was degraded to evaluate the photocatalytic activity of N-TiO2 immobilized on glass spheres. N-TiO2 sample with N/Ti weight ratio of 0.34% exhibits highest visible photocatalytic activity and the removal rate of CIP reached 90% in 90 min under visible light irradiation. The photocatalytic efficiency was hardly reduced after 5 cycle experiments, indicating that the recyclability of immobilized N-TiO2 was well. The kinetic model of degradation of CIP was confirmed as a first-order kinetic reaction model. The degradation products of CIP were analyzed by ultra-performance liquid chromatography tandem quadrupole time of flight mass spectrometry (UPLC-Q-TOF MS). A database containing 49 kinds of the degradation products of CIP already reported in the papers was established to screen the UPLC-Q-TOF MS results. 17 kinds of degradation products were found and the possible degradation pathways to CIP were inferred. The toxicological properties of these degradation products were assessed by computer software simulation. In this study, a new, simple and stable immobilization method was used to prepare N-TiO2 immobilized on glass spheres, and a rapid screening method for the degradation products of CIP was established.