A novel discovery of a heterogeneous Fenton-like system based on natural siderite: A wide range of pH values from 3 to 9

Abstract Natural iron-bearing minerals have been proven to be effective for activating H2O2 to produce OH, which can be used to degrade organic pollutants. In this study, the performance of siderite to degrade sodium sulfadiazine via catalytic H2O2 degradation was investigated at different solution pH values from 3 to 9. An interesting discovery was made: the performance of the siderite-H2O2 system was excellent under acidic, neutral, and even alkaline conditions. The influence of various factors (e.g. initial concentration, anions, natural organic matters, etc.) on the system under different pH conditions was investigated, which confirmed that siderite exhibited an excellent catalytic performance. By combining EPR characterization with scavenger research, it was proposed that dissolved iron (Fe2+) mainly initiated the homogenous Fenton reaction to degrade pollutants under acidic conditions, while structural Fe2+ species present in siderite triggered Fenton-like reactions under neutral or even alkaline conditions. From the SEM and XPS characterizations, oxidation and dissolution of Fe2+ on the surface were also observed, confirming our inference concerning the different reaction mechanisms. The experimental findings show that this siderite-H2O2 system can be used in solutions with pH values from 3 to 9 and that siderite plays a positive role in soil and groundwater remediation when H2O2 is used as an oxidant.