Formation of methyl iodide in sodium iodide solutions in the presence of acetic acid and formic acid under gamma irradiation conditions

It was confirmed that the pH of NaOH solution (pH 12) could be lowered to pH 6 or less, where I₂ was chemically stable, by radiolysis products of air and water. It was also confirmed that acetic acid (CH₃COOH) or formic acid (HCOOH) can act as a source material for CH₃I formation if these organic acids and I^- have specific concentration ratios and the solution pH is maintained within a specific range under gamma irradiation conditions. In the case of CH₃COOH mixed solutions, a high concentration of CH₃I was formed at a pH lower than the pK_a (= 4.76), where the radiolysis rate of CH₃COOH was relatively low. In the case of HCOOH mixed solutions, the formation of CH₃I was confirmed under the conditions of satisfying a pH of 3 or more, where radiolysis of HCOOH is inhibited, and a pH of 6 or less, where I₂ is stably present. (author)