Mn3O4-ZnMn2O4/SnO2 nanocomposite activated peroxymonosulfate for efficient degradation of ciprofloxacin in water

This study successfully synthesized Mn3O4-ZnMn2O4/SnO2 composite to activate peroxymonosulfate (PMS) for the efficient degradation of ciprofloxacin (CIP). The results showed that the Mn3O4-ZnMn2O4/SnO2/PMS system could effectively degrade CIP in a wide range of pH from 3 to 9, and under the optimal reaction conditions (catalyst = 0.35 g/L, PMS = 1.0 g/L and pH = 6.05) CIP could be degraded by 94.9 % within 30 min. The presence of co-existed substrates HCO3- showed a slight inhibition on the degradation of CIP, while the effect of the remaining substrates was basically negligible. The quenching experiments and electron paramagnetic resonance (EPR) analysis revealed that both non-radical (O-1(2)) and free radicals (SO4 center dot-, O-2(center dot-) and (OH)-O-center dot) played a role in the degradation of CIP, and the non-radical O-1(2) was dominant. It is noteworthy that electrochemical tests and density functional theory (DFT) calculations demonstrated that the electron transfer occurring between SnO2 and Mn3O4-ZnMn2O4 resulted in higher PMS activation properties of the composite. In addition, the three degradation pathways of CIP and the toxicity of the intermediates were identified by liquid chromatography mass spectrometry (LC-MS) and Toxicity Estimation Software (T.E.S.T.), respectively. Finally, to improve the reusability of Mn3O4-ZnMn2O4/SnO2 powdered catalyst, the corresponding microporous filter membrane were synthesized and exhibited good stability.