Iron-modified granular sludge biochar-based catalysts for improved Rhodamine B degradation by activating peroxymonosulfate

Anaerobic granular sludge (AnGS) is a potential resource for biochar production due to its unique microstructure and high organic contents. In this study, Fe 3 O 4 -loaded biochar derived from AnGS as a catalyst for peroxymonosulfate (PMS) activation was synthesized through iron modification and pyrolysis at different temperatures. The biochar characterization indicated that surface area (249.145 m 2  g −1 ) and microporosity (131.819 m 2  g −1 ) were significantly enhanced at 800 °C. Furthermore, the excellent magnetic properties of the iron-modified biochar at 800 °C (S@Fe-800) (45.28 emu g −1 ) were confirmed, in which Fe 3 O 4 was identified as the dominant reactive species. S@Fe-800 exhibited remarkable PMS activation ability for organic pollutants, which displayed superior Rhodamine B (RhB) removal efficiency. Results from the quenching experiments and electron paramagnetic resonance (EPR) detections demonstrated that the reactive oxidizing species (ROS), including sulfate radical (SO 4 •− ), were generated in the S@Fe-800/PMS system. Meanwhile, the significant intermediates and possible degradation path of PMS decomposition over RhB were proposed. It is believed that this work provides an effective method for organic contaminants removal and a green utilization route for AnGS.