Iron oxychloride composite sludge-derived biochar for efficient activation of peroxymonosulfate to degrade organic pollutants in wastewater

The reuse of sewage sludge is still a challenging issue for wastewater treatment plants. In this study, a composite catalyst (FeOCl-SBC) was innovatively synthesized to activate peroxymonosulfate (PMS) to degrade organic pollutants in wastewater, which was obtained by sludge-derived biochar (SBC) modified by iron oxychloride (FeOCl). The addition of FeOCl triggered the increase of carbonyl groups (CO) on biochar, which promoted the generation of reactive oxygen species (ROS) and accelerated the catalytic rate. Compared with SBC/PMS (0.0993 min−1) and FeOCl/PMS (0.0215 min−1) systems, the kinetic reaction rates of FeOCl-SBC/PMS (0.2107 min−1) for organic pollutants were increased by 2.1 and 9.8 times, respectively. FeOCl-SBC/PMS system had a wide pH range (3–9) and maintained 85% removal rate after 10 cycles. CO groups and Fe species (Fe3+/Fe2+) played an important role in the generation of singlet oxygen (1O2) and superoxide radical (O2•-) in FeOCl-SBC/PMS system. This work provides a viable strategy for the resource utilization of sludge and efficient treatments of organic wastewater.