Experimental and theoretical aspects of biochar-supported nanoscale zero-valent iron activating H₂O₂ for...

Ciprofloxacin has been frequently detected in water environment, and its removal has become a significant public concern. Biochar-supported nanoscale zero-valent iron (BC/nZVI) to activate hydrogen peroxide (H₂O₂) has many advantages on promoting the removal of organic contaminants. In this paper, the BC/nZVI activating H₂O₂ degradation of ciprofloxacin was systematically investigated by experimental and theoretical approaches. The morphologies and property analysis showed that nZVI particles distributed uniformly on the biochar surface, which mainly include ^-OH, >CO and COC and CO groups. Different reaction conditions were compared to define the optimal conditions for ciprofloxacin removal in BC/nZVI/H₂O₂ system. More than 70% of ciprofloxacin was removed in the optimal conditions: acidic condition (pH 3∼4), low doses of H₂O₂ (20 mM), and temperature of 298 K. The hydroxyl radical (^•OH) oxidation was the primary pathway in BC/nZVI/H₂O₂ degradation of ciprofloxacin process. The theoretical calculation indicated that hydrogen atom abstraction (HAA) pathways were the dominant oxidation pathways contributing 92.3% in overall second‒order rate constants (k) of ^•OH and ciprofloxacin. The current results are valuable to evaluate the application of BC/nZVI activating H₂O₂ degradation of ciprofloxacin and other fluoroquinolone antibiotics in water treatment plants.