Determination of persulfate based on the principle of the oxidation of chloride ion

Persulfate (PS) is a widely used oxidant for the chemical oxidation of organic pollutants. The accurate measurement of PS concentration is crucial for the practical application process. The iodometry is the most recommended method for PS determination, and its principle is based on the redox reaction between S2O82− and iodide ions. However, hydrogen peroxide (H2O2), an important intermediate product in the process of PS use, often leads to abnormally high determination concentrations of PS. Given this, a novel method was developed for the determination of PS based on the principle of the oxidation of chloride ion (Cl−). The concentration of PS is calculated according to the consumption of Cl− concentration, which is not disturbed by H2O2. The optimized test conditions were explored as: C(H+) = 2 mol/L, T = 80 ℃, C(Cl−):C(PS) = 4:1 and t = 30 min. Under the optimized conditions, the limit of detection and the limit of quantification of PS concentration determined by this method were 0.26 g/L and 0.85 g/L, respectively. And the linear range of the PS determination was 1–100 g/L with an error of 0.53%-12.06%. The spike recovery rate for determining PS concentration in the actual wastewater ranged from 94.07%-109.52%. Interfering factors such as H2O2, Fe3+, MnO2 and natural organic matter had almost no effect on the results. This method could not only accurately determine the concentration of PS in industrial wastewater, but also determine the purity of PS industrial products.