Catalytic ozonation with N, S co-doped sludge biochar for decontamination: Performance and mechanistic insights

Waste-derived biochar catalysts are widely used in catalytic ozonation. However, biochar is often constrained by insufficient surface active sites and low interfacial electron transfer efficiency. In this work, nitrogen (N) and sulfur (S) co-doped sediment-derived biochar (C-N 1 S 2 -600) was prepared by one-step pyrolysis using a mixed compost of black-odorous sediment, reed straw, and food waste as precursors, with melamine and thiourea using as the N and S sources, respectively. The optimized C-N 1 S 2 -600 has a well-developed mesoporous structure, abundant structural defects, and numerous reactive sites originating from N/S–C coordination. Ozonation with C-N 1 S 2 -600 achieved 62.8% Deethylatrazine degradation, which was significantly higher than that of ozonation alone (13.9%) and ozonation with pristine biochar (33.1%). C-N 1 S 2 -600 also exhibited excellent reusability over five consecutive cycles and maintained high performance in secondary effluent. Reactive species identification confirmed that C-N 1 S 2 -600 facilitated the conversion of O 3 into • OH. Theoretical calculations further revealed that N, S co-doping induced a more non-uniform surface charge distribution and narrowed the orbital energy gap, providing electronic-level insights into enhanced O 3 adsorption, interfacial electron transfer, and reactive oxygen species generation. C-N 1 S 2 -600 exhibited good operational stability and tolerance to matrix interference under the tested conditions. This study provides a feasible strategy for converting solid-waste-derived biochar into efficient carbonaceous catalysts for advanced wastewater treatment, and offers a promising strategy for micropollutant abatement and wastewater purification by catalytic ozonation with high-performance biochar catalyst.