Formation of iodinated products in Fe (II)/peroxydisulfate (PDS) system

The transformation of iodide (I) and hypoiodous acid (IO) by Fe (II)-activated peroxydisulfate (PDS) in the presence of natural organic matter (NOM) was investigated. In the water of a reservoir in Shenzhen, four kinds of organic matter were detected: iodoform > diiodo-bromomethane > dibromo-iodomethane > dichloromethane. As pH increased from 3 to 10, I conversion rate decreased from 31.0% to 11.0%. There is basically no iodic acid (IO3-) generated under alkaline conditions, probably due to these organic matters. When PDS concentration is low, PDS can oxidize part of I to IO, and the oxidation of I into IO3- reaction and continued oxidation reaction exist at the same time, so some IO3- is generated in the system. As the proportion of Fe (II) increases, the generation rate of IO 3 gradually increases. When Fe2+/PDS is 1:5, 2:5, and 3:5, the conversion rates of IO3- are 4.7%, 6.5%, and 8.4%, respectively. There are two main reasons for this: (i) the reaction of IO- produced in the system with humic acid (HA) inhibits the further conversion of IO- to IO3-; (ii) both HA and I- in the system can react with PDS, resulting in a reduction in the oxidation rate of I-.

Automated summary

The research found that as the pH increased, the conversion rate of iodide decreased and there was basically no generation of iodic acid under alkaline conditions, possibly due to the presence of organic matter. Additionally, the presence of Fe (II) activated peroxydisulfate was found to increase the generation rate of hypoiodous acid.