Catalytic degradation of ciprofloxacin by magnetic CuS/Fe2O3/Mn2O3 nanocomposite activated peroxymonosulfate: Influence factors, degradation pathways and reaction mechanism

In the study, CuS/Fe2O3/Mn2O3 magnetic nanocomposite was successfully synthesized and the properties were investigated via a series of characterization. Subsequently, the magnetic nanocomposite was applied to activate peroxymonosulfate (PMS) for ciprofloxacin (CIP) degradation. The results showed that the CuS/Fe2O3/Mn2O3 magnetic nanocomposite possessed higher catalytic performance for ciprofloxacin degradation than bare CuS and Fe2O3/Mn2O3 composite. The degradation process of CIP was suitable for the pseudo-first-order kinetic model and the highest rate was reached 0.10083 min(-1). And under the optimized conditions (catalyst = 0.6 g.L-1, PMS= 0.6 g.L-1, pH= 5.84, C-0= 0.2 g.L-1 and t= 120 min), the efficiency of 88% and 48.6% were corresponding to degradation and mineralization of ciprofloxacin, respectively. In addition, the key factors of degradation process such as catalyst dosage, PMS concentration, initial pH value and common anions were investigated. And the results indicated that the degradation efficiency of ciprofloxacin was reduced, which affected by the common anions in order of Cl- > SO42- > NO3- > HCO3- > Humic acid. Besides, several intermediates of ciprofloxacin were detected and the plausible degradation pathways were proposed. In addition, the underlying reaction mechanism was proposed. Meanwhile, the results of free radical quenching experiment and electron paramagnetic resonance (EPR) spectra indicated that both (OH)-O-center dot and SO4 center dot- radicals were existed in the reaction system and the %OH radicals had a conquer role in the degradation progress. Moreover, the stability and reusability of CuS/Fe2O3/Mn2O3 magnetic nanocomposite were evaluated, which the degradation efficiency still reached 72% after five times used. Ultimately, the as-constructed CuS/Fe2O3/Mn2O3 magnetic nanocomposite might be a candidate to the removal of refractory pollutants in environmental remediation.