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 earthabundant 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 (1O2) was shown to play a dominant role in OTC degradation. At the same time, further investigation revealed that hydroxyl radicals (& sdot;OH), superoxide radicals (O2 & sdot;- ), and dissolved oxygen (DO) all contributed to 1O2 production. This work offers a potential technology for the effective degradation of antibiotic-contaminated wastewater.