Experimental and theoretical aspects of biochar-supported nanoscale zero-valent iron activating H2O2 for ciprofloxacin removal from aqueous solution

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, > C=O and C-O-C and C-O groups. Different reaction conditions were compared to define the optimal conditions for ciprofloxacin removal in BC/nZVI/H(2)O(2 )system. More than 70% of ciprofloxacin was removed in the optimal conditions: acidic condition (pH 3 similar to 4), low doses of H2O2 (20 mM), and temperature of 298 K. The hydroxyl radical COH) 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 center dot 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.