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

Abstract

• Cobalt adsorbed on ferric sludge was recycled to create bimetallic catalyst via a facile solvothermal method. • Co/Fe nanocomposites derived from ferric sludge (CoFe@FS) exhibited an excellent performance toward PMS. • SO 4 •− , • OH, O 2 •− and 1 O 2 were produced from PMS activation by synergetic effect of Co and Fe on the catalyst surface. • The possible degradation mechanism of CIP is proposed based on DFT calculations and LC/MS analyses. • This is a cost-effective method to achieve “treating wastewater by waste residuals”. 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, CoFe 2 O 4 and SiO 2 crystals and presented excellent catalytic performance with 97.3% removal efficiency of 10 mg/L CIP within 15 min. Sulfate radicals (SO 4 •− ), hydroxyl radicals ( • OH) superoxide radicals (O 2 •− ) and singlet oxygen ( 1 O 2 ) all contributed to CIP degradation, and SO 4 •− 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.