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Chloride ion (Cl) is one of the most common anions in the aqueous environment. A mathematical model was developed to determine and quantify the impact of Cl on the oxidization rate of organic compounds at the beginning stage of the UV/persulfate (PS) and UV/HO processes. We examined two cases for the UV/PS process: (1) when the target organic compounds react only with sulfate radicals, the ratio of the destruction rate of the target organic compound when Cl is present to the rate when Cl is not present (designated as r/ r) is no larger than 1.942%; and (2) when the target organic compounds can react with sulfate radicals, hydroxyl radicals and chlorine radicals, r/ r, can be no larger than 60%. Hence, Cl significantly reduces the organic destruction rate in the UV/PS process. In the UV/HO process, we found that Cl has a negligible effect on the organic-contaminant oxidation rate. Our simulation results agree with the experimental results very well. Accordingly, our mathematical model is a reliable method for determining whether Cl will adversely impact organic compounds destruction by the UV/PS and UV/HO processes.

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