Sonophotocatalytic degradation of ciprofloxacin by Bi2MoO6/FeVO4 heterojunction: Insights into performance, mechanism and pathway

In this study, Bi2MoO6/FeVO4 core-shell heterojunction was adopted as sonophotocatalyst to investigate its sonophotocatalytic degradation of ciprofloxacin (CIP) under ultrasonic and visible light. The properties of Bi2MoO6/FeVO4 sonophotocatalyst were analyzed by XRD, FTIR, SEM, TEM, BET, DRS, XPS, PL and EIS. The effects of different operating parameters on the sonophotocatalytic degradation performance of CIP were investigated. Under the optimal operating conditions, a CIP degradation efficiency of 98.2 % and a mineralization rate of 68.9 % could be achieved after 60 min of reaction. Kinetic studies showed that the degradation process obeyed a pseudo-first-order reaction with a rate constant of k(sonophotocatalytic) > k(photocatalytic) > k(sonocatalytic). Before and after the addition of H2O2, the sonophotocatalytic degradation of CIP reached high synergy values of 2.02 and 2.50, respectively. The synergistic effect of degradation can be attributed to the generation of (OH)-O-center dot, O-center dot(2)- and h(+) in the system. Contribution rate calculation displayed that (OH)-O-center dot and h(+) were the most significant reactive oxygen species. In addition, twenty degradation products were identified by HPLC-MS analysis, and the toxicity of the degradation products was further analyzed by ECOSAR. Ultimately, three potential degradation pathways for CIP were proposed.