Aquatic environment

Involvements of chloride ion in decolorization of Acid Orange 7 by activated peroxydisulfate or peroxymonosulfate oxidation

Ping Wang , Shiying Yang , Liang Shan , Rui Niu , Xueting Shao


Received December 15, 2010,Revised February 19, 2011, Accepted , Available online November 04, 2011

Volume 23,2011,Pages 1799-1807

The effects of chloride anion (Cl-) (up to 1.0 mol/L) on the decolorization of a model compound, azo dye Acid Orange 7 (AO7), by sulfate radical (SO4) based-peroxydisulfate (PS) or peroxymonosulfate (PMS) oxidation under various activated conditions (UV254 nm/PS, Thermal (70℃/PS, UV254 nm/PMS, Co2+/PMS) were investigated. Methanol and NH4+ were used as quenching reagents to determine the contributions of active chlorine species (dichloride radical (Cl2) and hypochlorous acid (HClO)). The results indicated that the effects of Cl- on the reaction mechanism were different under various activated conditions. For UV/PS and Thermal/PS, the inhibition tendency became more clear as the Cl-concentration increased, probably due to the reaction between Cl- and SO4 and the generation of Cl2 or HClO. For UV/PMS, Cl- did not exhibit inhibition when the concentration was below 0.1 mol/L. As Cl- concentration reached to 1.0 mol/L, the decolorization rate of AO7 was, however, accelerated, possibly because PMS directly reacts with Cl- to form HClO. For Co2+/PMS, Cl- exhibited a significant inhibiting effect even at low concentration (≤ 0.01 mol/L). When Cl- concentration exceeded 0.1 mol/L, the activation of PMS by Co2+ was almost completely inhibited. Under this condition, HClO maybe played a major role in decolorization of AO7. The results implicated that chloride ion is an important factor in SO4-based degradation of organic contamination in chloride-containing water.

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