Effective degradation of OTC by Co-L@C cathode in heterogeneous Electro-Fenton system: Preeminent role of singlet oxygen species

Heterogeneous electro-Fenton (hetero-EF) system was one of the most promising approaches for treating antibiotic-laden wastewater. However, the rational design of cost-effective, eco-friendly, and efficient earth-abundant electrocatalysts remains a significant challenge. This study synthesized a novel catalyst, lignin-based metal biochar (Co-L@C), from coniferous lignin via hydrothermal reaction and temperature-controlled pyrolysis. The results demonstrated that Co-L@C achieved nearly 100 % oxytetracycline hydrochloride (OTC) removal within 30 min employing the hetero-EF system, consistently exhibiting efficient OTC degradation rates across a wide pH range (3−9) and in various practical water matrices. In conjunction with the burst test and electron paramagnetic resonance (EPR) analysis, singlet oxygen ( 1 O 2 ) was shown to play a dominant role in OTC degradation. At the same time, further investigation revealed that hydroxyl radicals (·OH), superoxide radicals (O 2 ·− ), and dissolved oxygen (DO) all contributed to 1 O 2 production. This work offers a potential technology for the effective degradation of antibiotic-contaminated wastewater.