An oxidation process of tetracycline with low products toxicity by Fe single-atom peroxydisulfate activator from...

Recently, advanced oxidation processes based on single-atom catalysts have been extensively adopted in water treatments. Although some studies have identified low toxicity in degradation products, the mechanistic understanding remains unclear. In this work, an efficient catalyst named BC-Fe was developed by anchoring atomically dispersed Fe onto biochar (BC) derived from microalgae using a convenient impregnation method. The catalyst of BC-Fe enhanced performance in activating peroxydisulfate (PDS) for the degradation of tetracycline (TC). The BC-Fe/PDS system demonstrated faster TC degradation rate constant of 0.073 min^-1. Mechanism investigations revealed that the atomically dispersed Fe-N₄ sites activate PDS via efficient electron transfer, generating high-valent metal-oxo (HVMO) species as the primary reactive oxidants. These HVMO species selectively oxidized electron-rich moieties in TC, leading to progressive ring-opening and mineralization into low-toxicity intermediates. Moreover, TC served as an electron donor to the HVMO species, enabling their reduction and forming a favorable cycle of valence states of Fe. This work provides an efficient and environment-benign strategy for the oxidation of antibiotics with minimal secondary pollution.