Enhanced catalytic degradation of ciprofloxacin with FeS/SiO microspheres as heterogeneous Fenton catalyst: Kinetics, reaction pathways and mechanism.

In this study, the application of FeS/SiO microspheres as a catalyst to activate HO for the degradation of ciprofloxacin (CIP) was systematically investigated. Results demonstrated that the presence of SiO microspheres on the surface of FeS could effectively make the reaction of aqueous Fe and HO smoothly continuous by controlling the release of aqueous Fe from FeS. Nearly 100% of CIP was degraded after 60min under the optimum conditions. A superior performance on the CIP degradation and high reusability of the catalyst was obtained in FeS/SiO microspheres activated HO system. A low concentration of ethylene diamine tetraacetie acid (EDTA) did positively affect the degradation rate of CIP. A synergetic effect between adsorption and oxidation processes contributed to the significant enhancement of CIP degradation. Seven oxidation intermediates were identified during the CIP degradation process, and the direct HO oxidation proved to be a main CIP degradation pathway. For degradation pathway of CIP, oxidation of piperazine ring would be its first step, followed by cleavage of the heterocyclic ring. Subsequently, the substitution, hydroxylation and decarboxylation processes occurred. This is the first report on the feasibility of FeS/SiO microspheres activated HO system for the enhanced degradation of CIP.