Impact of Chloride Ions on UV/H₂O₂ and UV/Persulfate Advanced Oxidation Processes

Abstract

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/H2O2 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 rRCl–/rR) is no larger than 1.942%; and (2) when the target organic compounds can react with sulfate radicals, hydroxyl radicals and chlorine radicals, rRCl–/rR, can be no larger than 60%. Hence, Cl– significantly reduces the organic destruction rate in the UV/PS process. In the UV/H2O2 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/H2O2 processes.