The promoted Fenton degradation of norfloxacin by a S-ZnO modified MnFe2O4 with micro-acidic environment

This study synthesized MnFe2O4@S-ZnO with varying S-ZnO loading and investigated their catalytic activity towards Fenton degradation of norfloxacin (NOF). The MnFe2O4@S-ZnO/H2O2 system achieved 98.3 % of NOF removal within 60 min, with the catalytic activity enhanced by 1.8 times compared to MnFe2O4. XPS results indicated that Mn and Fe are the active catalytic sites. The doping of S elements accelerated the reduction rates of Fe3+ and Mn3+, thereby improving the utilization efficiency of H2O2 and generating more center dot OH radicals. The Lewis acidic sites on the surface of MnFe2O4@S-ZnO coordinated with and reduced the concentration of OH- in the suspension, thereby increasing the acidity of theMnFe2O4 catalyst surface, expanding the pH range of the Fenton reaction to alkaline conditions, allowing the composite material to maintain a NOF removal efficiency of over 90.0 % at even high pH (9.0-10.0). The presence of inorganic anions and humic acid (HA) played negative roles on the NOF degradation, but the MnFe2O4@S-ZnO/H2O2 system can still achieve a minimum NOF degradation of 62.8 % within 60 min. Moreover, the MnFe2O4@S-ZnO catalyst exhibited relatively high stability and possessed easy recoverability. Furthermore, this catalyst overcomes the pH limitations of the traditional Fenton reaction, demonstrating significant advantages and promising application prospects.