Adsorption of Gaseous ¹³¹I₂ and CH₃¹³¹I Onto Geological Materials

Abstract

The adsorption of gaseous iodine, I₂ and CH₃I, in typical rocks of Japanese ground formation such as granite, tuff, and sandstone is described. Adsorption coefficients (Ka) of crushed rock samples were determined by a column technique under dry or wet vapor conditions. The adsorption isotherm was identified as the Langmuir- or Henry-type equation. The Ka value of I₂ varied over two orders of magnitude and was 10² to 10³ times greater than that of CH₃I. The results suggested that the Ka values of I₂ and CH₃I were proportional to the specific surface areas of crushed rocks and the order of the coefficients was: granite < tuff < sandstone at the same grain size (300-µm diam). The specific surface area of the permeable ground formation was estimated by the Kozeny-Carman equation, consequently, the smallest value of Ka of the rocks was one-tenth to one-thirtieth less than that of crushed rock.