The mechanism of reaction between peroxodisulfate ion (S2O 82-), selenite (Se(IV)O32-) and Mn2+ as an inhibitor of selenite oxidation was studied using aqueous solutions composed of commercial reagents, as well as limestone-gypsum flue gas desulfurization (FGD) liquors sampled from coal fired power plants. The oxidation of selenite to selenate (Se(VI)O42-) is promoted by the sulfate ion radical (SO4-) which results from decomposition of S2O82-. In the presence of Mn2+, selenite oxidation was prevented due to the difference in rates of reaction with SO4-. The ratio of the oxidation rate constants of selenite and Mn2+ with SO4- was determined over a temperature range of 40-60 C, and was found to be little influenced by the various coexisting components in FGD liquors.
ASJC Scopus subject areas
- Environmental Chemistry