A novel methodology to estimate the importance of isotopic exchange in the CH3I adsorption by impregnated activated carbons

Activated Carbons (AC) are widely used in the ventilation lines of nuclear facilities for the removal of volatile iodine species. In this paper, new experimental methodologies have been developed in order to measure the BreakThrough Curves (BTC) of both radioactive and stable CH3I for KI-or TEDA-impregnated AC {T = 20 - 30 degrees C, dry conditions}. Non-impregnated and KI-impregnated AC were shown to display similar performances for the trapping of stable CH3127I. In that case, only physical interactions within the micropores were involved in the adsorption process. A significant improvement of the retention occurred after TEDA impregnation. Regarding the trapping of the gamma-labelled CH3I, a significant enhancement of AC performances during both retention and breakthrough phases is observed after KI impregnation due to the promotion of isotopic exchange phenomenon. Therefore, the contribution of KI, still rarely studied in the literature, was isolated for the first time from the other mechanisms (physisorption and chemisorption). The in-depth analysis of BTC data obtained under active and inactive conditions allowed quantifying the contribution due to isotopic exchange.

Automated summary

This paper develops new experimental methodologies to measure the BreakThrough Curves (BTC) of radioactive and stable CH3I for KI-impregnated activated carbon (AC). The results show that KI-impregnated AC has similar adsorption performance to non-impregnated AC for stable CH3127I, while AC impregnated with TEDA significantly improves the adsorption capacity. For the trapping of gamma-labelled CH3I, KI impregnation enhances the AC performance during both retention and breakthrough phases due to the promotion of isotopic exchange phenomenon.