Carbon paper-based Fe-co-Mn cathode synergistically enhances electro-Fenton system for non-radical degradation of 2-mercaptobenzothiazole

2-Mercaptobenzothiazole (MBT), a highly toxic industrial corrosion inhibitor containing a thiol group, poses severe threats to ecological and human health. In this study, a trimetallic cathode (FeCoMn@LNC-500) was fabricated by in situ growing oxygen-vacancy-rich FeCoMn-LDHs on carbon paper followed by carbonization at 500 °C. FeCoMn@LNC-500 exhibited a cylindrical fiber-rod structure decorated with numerous densely aggregated spherical particles, which increased the electrochemical active surface area and reduced the charge-transfer resistance. Under optimal conditions, FeCoMn@LNC-500/EF achieves a degradation rate of 100% within 70 min through singlet oxygen ( 1 O₂) mediated non-radical oxidation (k = 0.0557 min −1 ). The removal efficiency achieved with this cathode was approximately 11.8, 5.0, 2.0, and 3.2 times higher than those of the PC-500, FeMn@LNC-500, CoMn@LNC-500, and CoFe@LNC-500 cathode systems, respectively. The outstanding degradation performance is primarily attributed to the carbon paper's excellent conductivity, which enhances the in-situ synergistic cycling of Co, Fe, and Mn to accelerate the Fenton reaction while also improving system stability, as demonstrated by a 7-cycle operational test and the detection of extremely low metal-ion leaching. Quenching experiments and electron paramagnetic resonance (EPR) spectroscopy confirmed that the non-radical 1 O₂ played a dominant role in the oxidation process. HPLC-MS analysis revealed the degradation mechanism and pathway of MBT: non-radical-dominated selective cleavage of the S N bond followed by stepwise mineralization. The carbon-paper-based cathode developed in this work provides insights into the electro-Fenton degradation of thiol-containing wastewater and is expected to offer a new strategy for the efficient treatment of coal-chemical pipeline wastewater.