Magnetic Co/Fe nanocomposites derived from ferric sludge as an efficient peroxymonosulfate catalyst for ciprofloxacin degradation

Ferric sludge, generated during drinking water purification process, can be considered as a promising support with potential iron resource. Herein, magnetic bimetallic Co/Fe nanocomposite derived from ferric sludge (CoFe@FS) was created via a facile solvothermal treatment and employed as an efficient peroxymonosulfate (PMS) activator for the elimination of antibiotic ciprofloxacin (CIP) in water. CoFe@FS exhibited nano-sphere structure with the composites of CoO, CoFe2O4 and SiO2 crystals and presented excellent catalytic performance with 97.3% removal efficiency of 10 mg/L CIP within 15 min. Sulfate radicals (SO4•−), hydroxyl radicals (•OH) superoxide radicals (O2•−) and singlet oxygen (1O2) all contributed to CIP degradation, and SO4•− functioned as the dominant reactive species in this activation system. CoFe@FS composite exhibited great reusability due to the strong Co/Fe-Si interaction and was able to regenerate by a simple solvothermal process. The CIP degradation mechanism in the CoFe@FS/PMS system were also proposed based on density functional theory (DFT) calculations and analysis of intermediate products. Overall, the magnetic Co/Fe bimetallic catalyst derived from ferric sludge could be employed as high-efficiency and low-cost candidate for the degradation of refractory organic contaminants. This work not only provides a promising reclamation strategy of water treatment waste from ferric sludge to high-effective catalyst, but also clarifies the mechanisms of PMS activation and CIP degradation. The more stable bimetallic CoFe catalysts derived from waste sludge need to be developed in the future study to relieve the occurrence of metal leaching.