Nonradical pathway in peroxymonosulfate-based Fenton-like reactions triggered by the active Fe-Cu dual sites encapsulated in endogenous N-rich biochar

Fabricating a high-performance catalyst for peroxymonosulfate (PMS) activation via efficient nonradical pathways remains a crucial challenge. Herein, we developed a new strategy to fabricate an efficient PMS activator (FeCu@NBC 700 ) with synergistic Fe-Cu dual sites encapsulated in nitrogen (N) self-doped biochar derived from waste soybean dregs. The FeCu@NBC 700 catalyst achieved 98.55% tetracycline (TC) removal and 90.56% PMS utilization within 60 min, with excellent stability across varying pH conditions, realistic water matrices, and continuous-flow operation. Characterizations confirmed that the N-rich carbon matrix (NBC 700 ) facilitated the in-situ formations, enhanced stabilizations, and full dispersions of low-valence Fe(0)/Fe(II) and Cu(0)/Cu(I) species, which participated as main active components for PMS activation. Density Functional Theory (DFT) calculations on the Fe-Cu bimetallic system showed electronic coupling converges their d -band centers, optimizes PMS adsorption energy (-4.45 eV), and promotes multi-electron transfer (1.45 e⁻). Mechanistic studies, including quenching tests, electron paramagnetic resonance (EPR) tests, galvanic oxidation process (GOP), and methyl phenyl sulfoxide (PMSO) probing experiments, demonstrated that TC degradation proceeded via a multiple nonradical pathway dominated by singlet oxygen (¹O 2 ) from superoxide ( O • − 2 ) disproportionation, supplemented by an electron transfer pathway (ETP) and participation of high-valent metal species (HMS). Ecological Structure-Activity Relationship (ECOSAR) analysis and seed germination tests confirmed significant reductions in the toxicity of degradation intermediates. This work provides an insight into bimetallic synergy for multi-pathway nonradical oxidation applied in PMS-based Fenton-like reactions and a waste-valorization design paradigm.