Involvements of chloride ion in decolorization of Acid Orange 7 by activated peroxydisulfate or peroxymonosulfate oxidation |
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Authors: | Ping Wang Shiying Yang Liang Shan Rui Niu and Xueting Shao |
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Institution: | 1. Key Laboratory of Marine Environment and Ecology, Ministry of Education, Qingdao 266100, China; College of Environmental Science and Engineering, Ocean University of China, Qingdao 266100, China 2. Key Laboratory of Marine Environment and Ecology, Ministry of Education, Qingdao 266100, China; College of Environmental Science and Engineering, Ocean University of China, Qingdao 266100, China; Department of Civil and Structural Engineering, The Hong Kong Polytechnic University, Kowloon, Hong Kong, China |
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Abstract: | 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 (UV254nm/PS, Thermal (70°C/PS, UV254nm/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 (HCIO)). 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 HCIO. 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 HCIO. 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, HCIO 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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Keywords: | chloride anion activated peroxydisulfate oxidation activated peroxymonosulfate oxidation radicals decolorization |
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