Formation of Organic Iodides upon Heating Nitric Acid Solutions Containing Carrier-Free lodine-131

Abstract

When nitric acid solution containing carrier-free "'I was heated, a fraction of the '"I was converted to organic iodides, among which methyl iodide was a major component. The yield of organic iodides showed a strong dependence on the concentration of nitric acid. Furthermore, the yield curve referred to reaction time revealed the particular characteristic of a hump appearing in the case of diluted nitric acid solutions. The distribution of I3'I among the various oxidation states in the acid solution has also been studied in its relation to reaction time. The results obtained indicate that organic iodide formation is related with the Io-IOa-oxidation step. The yield curve of the organic iodides is discussed qualitatively, by assuming an intermediate state I* existing between two extreme states of oxidation.

A Literature Survey to Identify Potentially Volatile Iodine-Bearing Species Present in Off-Gas Streams

“…Volatile organic iodides can be formed in otherwise pure HNO 3 (Nakamura et al 1973;Tachikawa 1973), whereas they do not form in other acids such as HCl, HClO 4 , and H 2 SO 4 (Nakamura et al 1973). Nakamura and coworkers found that the volatile organic iodides CH 3 I, C 2 H 3 I, C 2 H 5 I, n-C 3 H 7 I, and n-C 4 H 9 I were formed from very dilute 131 I 2 -bearing solutions.…”

“…Organic iodides may form in both aqueous and gas phases (Karhu 2001;Nakamura et al 1973;Taghipour 1999;Wren et al 1999). Organic compounds may be introduced to the processing systems, such as the dissolver, in small quantities with fresh reagents (e.g., nitric acid) or with recycle acid that might contain small amounts of alkanes (e.g., dodecane) or tri-n-butyl phosphate.…”

“…This indicates that efforts to volatilize CH 3 I or other organic iodides into the DOG may have limited success. As stated in Section 2.2, commercially obtained nitric acid contains organic impurities, and these impurities are known to react with iodine in the dissolver solution (Nakamura 1973). As the long-chain alkyl iodides do not volatilize into the DOG, residual organic iodine-bearing species may accumulate in the dissolver solution and be released into the VOG during solvent extraction processes.…”

“…Many of the iodides that result from these interactions are expected to remain with the organic phase (Sakurai et al 1995), even when the organic phase is washed to remove the radiolytic decomposition products. Nakamura et al (1973) found an extensive suite of organic iodides in their studies of nitric acid containing iodine. These included CH 3 I, C 2 H 3 I, C 2 H 5 I, n-C 3 H 7 I, and n-C 4 H 9 I.…”

Adsorption of methyl iodide on reduced silver‐functionalized silica aerogel: Kinetics and modeling

“…Therefore, unlike the ppm level in DOG, the iodine concentration in VOG could be in ppb level. The composition of the organic iodides existing in VOG could vary from methyl iodide (CH 3 I) to iodododecane (C 12 H 25 I), and the prior studies have identified CH 3 I and C 12 H 25 I to be the most representative of those organic iodides 6,9‐13 …”