Co-catalysis of N, S-codoped biochar toward photo-Fenton reaction for degradation of organic micropollutants in water

Photo-Fenton reaction can degrade organic pollutants with less consumption of H 2 O 2 and iron sources than conventional Fenton processes, but suffers from the problem of slow regeneration of Fe 2+ . Herein, an N, S-codoped biochar (NSB) co-catalyst was developed to accelerate iron redox cycling and enhance the oxidation of organic micropollutants in a visible-light-driven photo-Fenton system. Under optimized conditions (1.0 g L –1 of NSB, 1.0 mg L –1 of Fe 3+ , and initial pH = 3.5), the co-catalytic system (NSB+Fe 3+ +H 2 O 2 ) achieved 95% sulfadiazine (an antibiotic) degradation within 30 min, with an observed rate constant ( k obs = 0.108 min –1 ) 10 times higher than that of the photo-Fenton process (Fe 3+ +H 2 O 2 ). This co-catalytic photo-Fenton process exhibits broad applicability to degrade diverse micropollutants and in real water matrices (e.g., river water and tap water). Mechanistic investigations reveal that defects, pyridinic N, and thiophenic S sites on NSB facilitated the regeneration of Fe 2+ via electron transfer, thereby promoting the production of • OH and subsequent degradation of micropollutants. Thus, this research contributes to the advancement of the catalytic photo-Fenton reaction.