Z-scheme heterojunction WO3/BiOBr supported-single Fe atom for ciprofloxacin degradation via visible-light photocatalysis

Single-atom catalysts have drawn tremendous attention on account of their high activity, selectivity and stability. Z-scheme heterojunctions can effectively improve the utilization of optical energy due to the enhanced separation of photogenerated electrons and holes. In this work, several catalysts associated with single-atom Fe (FeSA) loaded on Z-scheme heterojunction WO3/BiOBr were prepared; their structure, morphology and photoelectric properties were analyzed; their photocatalytic degradation performance of Ciprofloxacin (CIP) was investigated; and the effects of initial pH, initial CIP concentration, catalyst dosage, light intensity, inorganic anions and humic acid on CIP removal rate were examined. Relevant results showed that the percentage of CIP removal by FeSA/WO3/BiOBr could reach 98.5% (120 min); the optimal conditions were pH= 9, [CIP]0 = 10 mg/L, [FeSA]0 = 0.8 g/L and Ilight= 500 W (100% degradation rate within 30 min);·O2- and h+ were the key active species. Results of the cyclic experiments suggested good stability of the catalyst. Furthermore, the mechanism of CIP photocatalytic degradation was proposed to be a synergistic mechanism of Z-scheme heterojunction migration and valence cycling between single-atom Fe2+ and Fe3+. Finally, the products and pathways of CIP degradation were analyzed.