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.