Figure 1. Schematic diagram of the continuous flow CH3I adsorption system
Dry air flowed through Dynacalibrator (VICI, Model 500), in which a permeation tube (VICI) was placed, as the carrier gas to generate CH3I. The CH3I concentration was controlled by the specific permeation tube model and the temperature of the permeation chamber. 500 sccm of gas mixture was preheated to 150 ℃ in the preheating coil wound around the adsorption column and then sent to the adsorption column (I.D.= 30 mm). In the adsorption column, one layer of Ag0-Aerogel pellets was placed on a tray and suspended under the microbalance. The microbalance has a variance of approximately 30 μg and a sensitivity of 0.1 μg. When the CH3I vapor was absorbed by Ag0-Aerogel pellets, mass change was measured by the microbalance and saved by the data acquisition system. During the adsorption process, the temperature was controlled by the furnace controller and N2 was used as the protective gas for the microbalance system.

Modeling

Multiple gas-solid adsorption models have been used in explaining adsorption kinetics of I2 and Organic Iodides including Linear Driving Force Model (LDFM), Shrinking Core Model (SCM), Volume Reaction Model (VRM) and Pore Diffusion Model (PDM).16,18,38,42-46 I2 adsorption on Ag0Z has been identified as the shrinking core process because the core shrinkage was observed by Nan.16Shown in Figure 2, a similar process was observed in CH3I adsorption on Ag0-Aerogel by cutting a partially reacted pellet in half. The yellow area is the reacted Ag0-Aerogel and the black area is the unreacted core. Therefore, the shrinking core model was selected to model the adsorption kinetics.