Biochar loaded with CoFe₂O₄ enhances the formation of high-valent Fe(IV) and Co(IV) and oxygen vacancy in the peracetic acid activation system for enhanced antibiotic degradation

Corn straw and sludge-derived biochar composite (BC) loaded with CoFe₂O₄ was successfully prepared to activate peracetic acid (PAA) for efficient degradation of tetracycline hydrochloride (TCH). Within 60 s, 96 % TCH removal efficiency was achieved through a non-free radical degradation pathway, primarily driven by singlet oxygen (¹O₂). The mechanism involves the electron-rich groups on the biochar surface, which facilitate the cleavage of the PAA O–O bond to generate •O₂⁻/¹O₂ and provide electrons to induce the formation of high-valent Fe(IV) and Co(IV). The oxygen vacancies on the surface of the CoFe₂O₄-loaded biochar composite (CFB-2) contribute partially to ¹O₂ production through their transformation into a metastable intermediate with dissolved oxygen. Moreover, elevated temperatures further enhance PAA activation by CFB-2, leading to increased reactive oxygen species (ROS) production through PAA decomposition, thereby promoting TCH removal. This study offers new insights into the catalysis of metal-loaded biochar for efficient TCH degradation via non-free radical generation.