One-pot fabrication of sludge-derived magnetic Fe,N-codoped carbon catalysts for peroxymonosulfate-induced elimination of phenolic contaminants.

The use of waste sludge as a precursor of catalysts for environmental applications has been encouraged during the past few years. In this study, a series of magnetic Fe,N-codoped carbon catalysts (UBC-x) were successfully prepared by a facile one-pot pyrolysis method using Fe-rich sludge and N-rich urea as the raw materials. By carefully controlling the mass ratio of urea/dry sludge (x = 0-3), a significant amount of N (1-10 mass%) were incorporated, and the UBC-x catalysts, especially UBC-0.5 and UBC-0.75, could be imparted with high catalytic activity, convenient magnetic separation and high recycle stability. Phenolic contaminants like phenol and bisphenol A (BPA) could be nearly completely removed through peroxymonosulfate (PMS)-induced degradation by using UBC-x as the catalysts under a wide pH range (2-11) and with the co-existence of water constituents (chloride Cl and sodium humate NaH, 0-50 mM). Among the several reactive oxidative species (ROS), singlet oxygen (O) was deemed as the main reactive species responsible for BPA degradation. Both Fe and N active sites contributed to the high catalytic activity of UBC-x, and their coordination made the catalysts rather stable with no significant Fe leaching under a wide pH range. Therefore, after an easy magnetic separation, the UBC-x could be recycled and reused efficiently in another BPA removal cycle. The as-synthesized magnetic Fe,N-codoped carbon catalysts provided a new route for sludge reutilization and showed potential applications in wastewater treatment.