Efficient degradation of alkyl imidazole ionic liquids by MnFe2O4-activated peracetic acid: Performance, mechanisms, and ecotoxicity assessment

Peracetic acid (PAA), an emerging oxidant in advanced oxidation processes, has attracted widespread attention in water treatment. However, there is still a lack of an efficient and environmentally friendly method for activating PAA to remove alkyl imidazolium based ionic liquids ([Bmim] + ) in water. This study introduces MnFe 2 O 4 /PAA system as an effective approach for the degradation of [Bmim] + , which have garnered significant attention due to their wide-ranging industry applications and potential biotoxicity. The degradation kinetics, mechanisms, pathways, and ecotoxicity (acute toxicity test and ecological structure-activity relationship program) of [Bmim] + were comprehensively investigated. The results showed that the highest removal efficiency of 1-Butyl-3-methylimidazolium chloride ([Bmim]Cl) reached 93.9 %. Electron paramagnetic resonance and quenching experiments confirmed that the reactive oxygen species (such as •OH and R-O•) participated in the degradation of [Bmim]Cl. Density functional theory calculations identified the imidazole ring of [Bmim] + as the primary active site for free radical attack. Thirteen oxidation products and two major reaction pathways were identified through ultra performance liquid chromatography/tandem mass spectrometry analysis, showing hydroxylation and carbonylation as the key reactions. Furthermore, ecotoxicity evaluations demonstrated that the degradation intermediates were harmless. This study demonstrates that the MnFe 2 O 4 /PAA system is an efficient and environmentally friendly technology for removing [Bmim]Cl, addressing a critical gap in advanced oxidation processes. Mechanism studies and theoretical calculation of MnFe 2 O 4 -activated PAA provide theoretical references for the PAA-based studies, which may further the commercial application of PAA in removing recalcitrant organic pollutants.