Adsorptive removal of gaseous methyl iodide by triethylenediamine (TEDA)-metal impregnated activated carbons under humid conditions

Sorption Properties of Activated Carbons for the Capture of Methyl Iodide in the Context of Nuclear Industry

“…Indeed, the computed qm (Table 4) values are decreasing from (0.204 ± 0.017) to (0.141 ± 0.007) g/g when moving from AC 1 -G to 1.6TEDA,KI/AC1 -G respectively. Nevertheless, TEDA functionalization enhances the chemical re actions leading to a specific storage of CH3 I molecules as stated in previous works [9][10][11][12]. Then, an increase of the energetic affinity displayed by the activated carbon towards CH3 I is expected.…”

“…Different trends can be noticed depending on the experimental conditions. In the first set of conditions, CH3 I adsorption is mainly governed by physisorption phenomena [8,9,12,49]. These phenomena are known to be almost sensitive to the micropore accessibility especially in the case of CH3 I (kinetic diameter of 0.5-0.6 nm) [8,50].…”

“…before KI and TEDA impregnation). Nevertheless, pore blockage phenomena are known to occur upon impregnation due to the presence of the incorporated agents within or at the micropores openings [9,12,16,36,37].…”

“…This deterioration in retention properties is assigned to an increase in both the adsorption temperature (from 35 to 75 °C) and the water vapor content (from 150 00 to about 130 000 ppmv). On the one hand, the presence of water vapor in large excess is known to in duce an adverse effect on CH3 I trapping by activated carbons, due to the adsorption competition between CH3 I and H2 O molecules [8,9,48]. More precisely, it was reported [56] that the adsorbed water molecules formed clusters interacting through hydrogen bonds with activated carbon porous network, making therefore the ac tive sites less accessible for iodine species.…”

“…TEDA reacts with CH3 I through a chemical reaction leading to a stronger fixation. This reactivity was reported to be dependent on the relative humidity [9]. For a totally dry atmosphere, the chemisorption of CH3 I is governed by an alkylation mechanism based on the SN 2 reaction [10,11].…”