Sewage sludge derived magnetic biochar effectively activates peroxymonosulfate for the removal of norfloxacin

Abstract

As an undesirable by-product of the wastewater treatment plants (WWTPs), sewage sludge (SS) caused considerable stress on the normal operation of WWTPs, because of its expensive disposal costs. On the other hand, exploiting resource utilization of the residual SS seems to be an attractive approach to resolve this problem. In this study, SS was thermally converted into biochar catalysts (SBC) under oxygen-limiting conditions. By using peroxymonosulfate (PMS) as the chemical oxidant, norfloxacin (NOR) could be effectively removed and the reaction was significantly accelerated after the addition of SBC. Specifically, over 90% of NOR was eliminated by the SBC800/PMS process within 70 min. As evidenced by the comprehensive mechanistic investigations, 1O2 as well as electron-transfer regime primarily participated in the NOR degradation process, while radical species played minor roles. More importantly, the endogenous iron substances endowed SBC with magnetic properties, making the efficient separation of SBC from water available. Eventually, the possible intermediates were tentatively identified by liquid chromatography-mass spectrometry and the corresponding degradation pathways were proposed. Overall, this research developed a novel method to achieve the remediation of NOR-contaminated water and elimination of the potential risks of SS simultaneously.