Synergistic activation of MgFe2O4/ZnO photocatalyst with peroxymonosulfate enables efficient degradation of ciprofloxacin: A study on radical multipath mechanisms

The widespread use of ciprofloxacin antibiotics poses substantial environmental and health threats due to their persistence in aquatic ecosystems. In this study, a light-responsive MgFe 2 O 4 /ZnO (MFOZ) composite was synthesized via a co-precipitation method for activating peroxymonosulfate (PMS) to degrade ciprofloxacin (CIP). The constructed heterojunction structure, with MgFe 2 O 4 nanoparticles uniformly anchored on ZnO, significantly increased the specific surface area (51.94 m 2 ·g −1 ) and enhanced light absorption, narrowing the bandgap to 2.91 eV. This unique configuration facilitated the separation of photogenerated charge carriers, as evidenced by a higher photocurrent density and lower electrochemical impedance compared to the individual components. Under light irradiation, the MgFe 2 O 4 /ZnO/PMS system achieved a 95 % CIP removal within 100 min, with a kinetic rate constant of 0.0262 min −1 , which is 5–11 times superior to that of the single-component systems. Radical quenching experiments and EPR analysis confirmed the involvement of •OH, SO 4 •⁻, O 2 •⁻, and 1 O 2 , among which O 2 •⁻ was identified as the primary contributor. The catalyst demonstrated remarkable stability, retaining over 80 % efficiency after five consecutive cycles, and maintained high efficacy in both tap and surface water matrices. Effective across a broad pH range (3.96–9.74), the system's performance was, however, inhibited by the presence of HCO 3 - and H 2 PO 4 - anions. The degradation pathway of CIP involved defluorination of the quinolone ring, oxidation of the piperazine ring, and C-F bond cleavage, ultimately leading to the formation of low-molecular-weight products. This work presents a stable and synergistic strategy that couples photocatalysis with PMS activation for antibiotic remediation, thereby advancing practical solutions for water treatment.