Activation of peroxydisulfate and peroxymonosulfate by zero-valent iron and FeCu bimetals for 4-chlorophenol oxidation in water

This work systematically evaluates the application of disc-milled iron‑copper (FeCu) bimetals for activating peroxydisulfate (PDS) and peroxymonosulfate (PMS), providing insights into both systems behavior. 4-chlorophenol (4-CP) was chosen as the model pollutant to evaluate the performance of bimetals compared to traditional iron-based activators (Fe2+ and Fe0). The influence of different factors was addressed, including i) bimetals composition (0, 5, and 50 % Cu content), ii) disc-milling, and iii) bimetals concentration. FeCu bimetal with 5 % Cu content showed a better synergy when combined with PMS, resulting in the highest 4-CP degradation, dechlorination, and mineralization (92 %, 62 %, and 60 %, respectively, within 120 min). Different quenchers and PMSO were used to identify the main reactive species in the bimetallic systems, showing the production of Fe4+ with both oxidants and a relevant contribution of 1O2 in the case of PMS. Finally, practical considerations for implementing the FeCu systems have been carefully evaluated, including the potential secondary effects on water quality due to iron and copper release, as well as the stability and reusability of these activators. Adjusting the final pH to 8.0 effectively precipitated dissolved metals, ensuring compliance with Italian environmental quality standards (Fe ≤ 2 mg/L and Cu ≤ 0.1 mg/L). Moreover, Fe5Cu bimetals have shown outstanding stability in repeated uses. Thus, this study introduces a novel, and eco-friendly approach for synthesizing active FeCu bimetals capable of efficiently activating oxidants, offering a promising solution for environmental pollution remediation. While optimal treatment conditions are thoroughly discussed, further studies are needed for full-scale application.