Rational electron tunning of magnetic biochar via N, S co-doping for intense tetracycline degradation: Efficiency improvement and toxicity alleviation

A cheap and recyclable biochar catalyst to degrade antibiotics via a nonradicals-dominated peroxydisulfate (PDS) activation process has attracted extensive attention due to environmental and economic feasibility. However, the mechanism and active sites are unclear, because of the more amorphous structure of biochar compared to the regular nano-carbon. This hinders the rational design of magnetic biochar for a stable and harmless nonradical degradation. Herein, based on magnetic chitosan-derived biochar (CSIN), N and S co-doping strategy was introduced for the rational electron design to achieve a transition from free radicals to nonradicals during the degradation. After modification, the nonradical pathway contributed 93.97% on tetracycline (TC) degradation with ¹O₂ as major species, resulting in 41.24% more degradation performance than pristine CSIN. Moreover, it also ensured broad pH applicability, strong environment stability, and cycling reliability during TC degradation. The intermediates produced by ¹O₂ attacks have significantly lower toxicity than those of free radicals. Therefore, this work serves as an illustration for biochar design used in market-responsive antibiotic degradation, encouraging new insights for the function-oriented catalyst design.