Spectrophotometric determination of peroxymonosulfate anions via oxidative decolorization of dyes induced by cobalt

Abstract

Dyes can be decolorized by the activation of peroxymonosulfate (PMS) in the presence of cobalt, and four good linear correlations between the depletion of dyes at their maximum absorption wavelengths and the concentration of PMS are demonstrated under the optimum conditions. For four types of samples, sensitive, rapid, and low-cost spectrophotometric methods are developed for the determination of PMS in aqueous solutions, which are based on the oxidative decolorization of the dyes with sulfate radicals generated by the conjunction of PMS and cobalt. The linear ranges and the detection limits are determined to be 0–80 μM and 0.08 μM for acid orange 7, 0–100 μM and 0.1 μM for methylene blue, 0–80 μM and 0.08 μM for methyl violet, and 0–40 μM and 0.04 μM for rhodamine B, respectively. When our proposed methods are used for the determination of the concentration of PMS with the treatment of 4-chlorophenol by the activation of PMS with cobalt, the results are as satisfactory as those obtained by using the classical iodometric method.