N-doped biochar from sewage sludge for catalytic peroxydisulfate activation toward sulfadiazine: Efficiency, mechanism, and stability

Sewage sludge-derived biochar (SBC) could remove organic contaminants in environment and reuse the sludge effectively. In this study, urea-doped SBC (NSBC) was prepared, characterized, and applied as heterogeneous catalytics to peroxydisulfate (PDS) activation. Sulfadiazine (SD), a widely used antibiotic, was used as a model pollutant to evaluate the efficiency and mechanism of this system. The degradation rate of SD increased to 100% after 4 h when 1 g/L of NSBC was added to the system with a SD concentration of 20 mg/L. In this study, it was confirmed that there were two important pathways in the degradation of SD by NSBC/PDS system: the free radical on the surface of NSBC and the nonradical (O-1(2)) in the solution. The doping of N atoms makes neighboring C atoms positively charged, thereby making the direct transfer of electrons with S2O82- and the generation of O-1(2) via nonradical pathway easy. In addition, the C=O functional group formed during the pyrolysis of NSBC can produce O-1(2) in a similar way. A total of 22 SD degradation products were identified, and 4 possible pathways were proposed. This study provide supplement for the degradation mechanism of organic compounds by carbonbased materials.

Automated summary

Sewage sludge-derived biochar can effectively remove organic contaminants in the environment and reuse sludge. In this study, urea-doped SBC was used as a catalyst for peroxydisulfate activation to degrade sulfadiazine, a widely used antibiotic. The degradation mechanism involves two pathways: the free radical on the surface of NSBC and the nonradical pathway in the solution, with N doping facilitating electron transfer and O-1(2) generation. A total of 22 degradation products of SD were identified, and 4 possible degradation pathways were proposed, providing insights into the degradation mechanism of organic compounds by carbon-based materials.