Degradation Efficiency and Toxicity Variation in Ozonation of 2,4,6-tri-chlorophenol with Interference of Cl-/Br-
As a typical raw material for industrial production,2,4,6-trichlorophenol(2,4,6-TCP)commonly coexists with inorganic halogen ions in the industrial wastewater.However,little literature have reported the effect of halo-gen ions on the oxidative degradation of 2,4,6-TCP.In this paper,the ozonation degradation kinetics and oxidation efficiency of 2,4,6-TCP were investigated under varying halogen ion conditions.Additionally,the toxic effects be-tween 2,4,6-TCP degradation intermediates as well as the alterations of solution toxicity were evaluated.The results showed that adding low concentration of Cl-(20 mmol·L-1)could increase the degradation rate of 2,4,6-TCP from 0.234 mol·min-1 to 0.237 mol·min-1,while high concentration of Cl-and Br-significantly inhibited the degrada-tion of 2,4,6-TCP.When the concentrations of Cl-and Br-respectively increased from 0 mmol·L-1 to 300 mmol L-1 and 100 mmol·L-1,the chemical oxygen demand(COD)removal rate of 2,4,6-TCP solution decreased by 17％and 18％,and the adsorbable organic halides(AOX)removal rate decreased by 15％and 55％after 2 h of ozone oxidation.The results indicated that 2,4,6-TCP was mainly degraded by the co-oxidation of O3,OH and O2·.Notably,the intermediate 2,6-dichloro-1,4-benzohydroquinone,2,6-dichloro-1,4-benzoquinone and 2,4,6-tribromo-phenol exhibited higher acute and chronic toxicity than 2,4,6-TCP.The ternary mixed toxicity test showed a syner-gistic toxicity effect between 2,6-dichloro-1,4-benzoquinone,2,6-dichlorophenol and 2-chlorophenol.The concen-tration of AOX was highly positively correlated with the toxicity unit of the 2,4,6-TCP solution,indicating a sub-stantial contribution of AOX substances to wastewater acute toxicity.Therefore,the potential ecological risks posed by AOX pollutants warrant further attention.
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