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@BC2-2) 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@BC2-2 showed considerably better CIP degradation efficiency (96.9% at 20 mg L-1) than traditional catalysts. Furthermore, Fe@BC2-2 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@BC2-2 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 (1O2) 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.