To understand the effect of temperature to the adsorption, 104 ppbv and 1044 ppbv methyl iodide (CH3I) adsorptions on reduced silver-functionalized silica aerogel (Ag0-Aerogel) at 100, 150 and 200 ℃ were performed. In the experiments, a significantly high uptake rate (3 – 4 times higher than that at 100 and 150 ℃) was observed for the 104 ppbv adsorption at 200 ℃. To explain such behavior, a potential reaction pathway was proposed and multiple physical analyses including nitrogen titration, x-ray photoelectron spectroscopy (XPS) and scanning electron microscopy (SEM) were performed. Based on the results, the contributing factors appear to be the formation of different Ag-I components induced by temperature, higher silver site availability, decreasing diffusion limitation, and increasing reaction rate described by the Arrhenius relationship.

The low concentration methyl iodides (CH3I) adsorption process on reduced silver-functionalized silica aerogel (Ag0-Aerogel) was studied. The kinetic data were acquired using a continuous flow adsorption system. Because the corresponding physical process was observed, the shrinking core model (SCM) was modified and applied. An average CH3I pore diffusivity was calculated, the CH3I-Ag0-Aerogel reaction was identified as a 1.37 order reaction instead of first order reaction, and the nth order reaction rate constant was determined. This modified SCM significantly increases the accuracy of adsorption behavior prediction at low adsorbate concentration. Modeling results indicate that the overall adsorption process is controlled by the pore diffusion. However, at low adsorbate concentration (<100 ppbv), the CH3I adsorption is limited to the surface reaction due to the low uptake rate in a predictable time period.