Dual heteroatom engineering-modulated cobalt catalysts for peracetic acid activation realized superior sulfadiazine degradation in water

The wide occurrence of sulfonamide antibiotics in water environments poses a great threat to ecological system and human health. Cobalt-based catalysts are well known for advanced oxidation processes (AOP), but the synergistic role of heteroatoms is still uncertain. In this work, a new type of heterogeneous Co based catalyst with sulfur as the ligand (Co@S-N-C) was transferred through a straightforward one-pot pyrolysis approach for efficient activating peracetic acid (PAA) to degrade sulfadiazine (SDZ). Systematic characterization confirmed that the co-doping by S and N in carbon induced the formation of several cobalt species (Co 0 , Co 2+ , and Co 3+ ) and built a unique electronic structure featuring in abundant defects and large specific surface area. The Co@S-N-C/PAA system exhibited exceptional catalytic efficacy, accomplishing total SDZ degradation in 25 min and a substantial mineralization rate of 78.2% within 90 min, markedly surpassing the performance of single heteroatom-doped catalysts (Co@N-C and Co@S-C). Mechanistic investigations indicated that •OH and CH 3 COO• contributed 66.4% and 34.1% to SDZ degradation, respectively. DFT calculations revealed that S-N co-doping increased the electron transfer from low-valent cobalt sites to PAA, promoting O-O bond splitting. The catalyst exhibited excellent stability with 71% activity retention and minimal Co leaching (5%) after four cycles. Based on these results, five primary degradation pathways for SDZ were proposed, and the results of ecotoxicity analysis showed that the transformation products were less toxic. Overall, this work provides significant insights into the development of high-performance dual-heteroatom-doped catalysts to form the PAA-mediated AOP for wastewater treatment.