Iron-doped Carex meyeriana Kunth biochars activate peracetic acid for efficient degradation of acid orange 7 dye in water: Key role of non-radical pathways

The development of printing and dyeing industry has led to the generation of substantial quantities of dye wastewater, posing significant risks to environment and human health. The advanced oxidation process based on peracetic acid (PAA) could be able to effectively and environmentally treat such wastewater. In this study, iron-doped/iron-undoped Carex meyeriana Kunth biochars were synthesized at 300, 500, and 700 °C to activate PAA for the degradation of acidic orange 7 (AO7) in water. Using 700 °C iron-doped biochar (Fe-KBC700) as the representative material, the effects of reaction conditions and water matrices on removal of AO7 were tested, the dominant reactive species, activation mechanism, and degradation pathway of AO7 were investigated, and the repeatability of Fe-KBC700 was evaluated. High pyrolysis temperature and the introduction of Fe enhanced the activation property of biochars. Fe-KBC700/PAA system could degrade 99.5 % of AO7 within 30 min, and the degradation rate of AO7 remains above 90 % in the pH range of 2.8–9 and complex water matrices. Non-radical pathways dominated AO7 degradation, with singlet oxygen and electron transfer processes playing primary roles, and high-valent metal-oxo species contributed secondarily. Free-radical pathways exhibited minimal contributions. Carbonyl groups (C O) and defect structures on biochar served as primary active sites. AO7 degradation initiated with cleavage of the azo bond, followed by decomposition into small-molecule products. Moreover, Fe-KBC700 degraded 85.6 % of AO7 after 5 cycles. This study could provide valuable insights into the major contributions of non-radicals in biochar activated PAA, and present an effective approach for the efficient treatment of dye wastewater. • Iron-doped Carex meyeriana Kunth biochars were synthesized at 300, 500, and 700 °C. • High pyrolysis temperature and iron-doping improved activation property of biochars. • Non-radical pathways ( 1 O 2 , ETP, and HVMe) dominated the degradation of AO7. • C O and defects on biochar were key active sites for non-radical species generation. • Fe-KBC700/PAA system exhibited strong anti-interference and reusability.