We investigated the impact of NO2-on degradation efficiency,products,and toxicity of 4-chloro-3,5-dimethylphenol(PCMX)during ferrate(Fe(Ⅵ))oxidation.Results demonstrated that Fe(Ⅵ)effectively degraded PCMX in water within the pH range of 7～9,achieving a 100％removal in 5minutes with a[Fe(Ⅵ)]∶[PCMX]ratio of 10∶1.The presence of 0.1～10mg/L humic acid(HA)significantly enhanced PCMX degradation.The addition of NO2 inhibited the reaction,and resulted in the formation of various nitrated byproducts.Quenching experiments indicated that high-valent iron species play a key role in this process.Toxicity assessment suggested that these nitrated byproducts and coupling products exhibited prolonged persistence and biotoxicity.For example,OP-6 and OP-7 have half-lives exceeding 180 days,bioaccumulation factors greater than 5000,and chronic toxicity values less than 1mg/L,which may pose certain environmental risks.
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