The morphology and structure of zero-valent iron nanosheets promote the activation of persulfate for degradation of ciprofloxacin

Herein, a biochar-supported zero-valent iron (ZVI) nanosheet catalyst (Fe@BC 2-2 ) for the activation of persulfate to degrade ciprofloxacin (CIP) was prepared using industrial kraft lignin and Fenton sludge as carbon and iron sources, respectively. Fe@BC 2-2 showed considerably better CIP degradation efficiency (96.9% at 20 mg L −1 ) than traditional catalysts. Furthermore, Fe@BC 2-2 exhibited CIP degradation efficiency above 96% in a wide pH range (3–11) and high resistance to interference from various inorganic anions and humic acid even under real water body conditions. The Fe@BC 2-2 catalyst showed good magnetic separation performance and maintained high CIP degradation efficiency (87.0%) after five degradation–regeneration cycles. CIP degradation was facilitated by ZVI nanosheets along with functional groups and defects on the surface of the biochar. As determined through radical-quenching experiments, both radical and non-radical pathways contributed to the degradation of CIP, with the non-radical pathway being dominant, especially with singlet oxygen ( 1 O 2 ) as the active species. The degradation pathway of CIP was inferred through the analysis of intermediate products, which showed lower toxicity than CIP. This work not only proposes a strategy for the utilization of traditional kraft pulping lignin and Fenton sludge but also presents an innovative catalyst for the degradation of antibiotics.