Degradation of ciprofloxacin by CuFe2O4/GO activated PMS process in aqueous solution: performance, mechanism and degradation pathway

Catalytic degradation of ciprofloxacin (CIP) was studied by using copper ferrite (CuFe2O4) nanoparticles coated on graphene oxide (CuFe2O4/GO) as a heterogeneous activator of peroxymonosulfate (PMS). CIP degradation efficiency by CuFe2O4/GO/PMS system was evaluated by affecting factors such as, pH of aqueous media, reaction time, different concentrations of PMS, various CIP and catalyst concentrations, trapping agents and water matrix inorganic components. Kinetic models of the catalytic oxidation process were also investigated. Also, based on quenching tests, a pathway of PMS activation and reactive species production in both solid and liquid phases was proposed. Results showed that under the optimum conditions (pH = 7, 2 mM PMS and 0.2 g/L catalyst), 98% of CIP (30 mg/L) and 45% of total organic carbon (TOC) were removed within 60 min. Pseudo-first-order kinetic model was the best fit with the experimental data of degradation process. The inhibiting effects of water inorganic species on CIP degradation were as follows: HCO3− >NO3− > Cl− > SO42-. CuFe2O4/GO remains active even after five cycles of reuse for CIP degradation and leaching of Fe and Cu metals in the solution was negligible. Transformation products of CIP by CuFe2O4/GO/PMS were analysed by GC-MS. Transformation products of CIP by CuFe2O4/GO/PMS were identified using GC-MS, and degradation pathways have been proposed. Investigating the free radicals showed that SO4•- radicals play an important role in the catalytic oxidative degradation process. CuFe2O4/GO in coupling with PMS can be utilised as an effective method to degrade/mineralise of antibiotics, due to the powerful catalytic activity, the generation of various free radicals, magnetically recyclable and the high stability and reusability potential.