Adsorption of iodine and water by reduced silver-exchanged mordenite (AgoZ) is experimentally and theoretically investigated to support the development of advanced modeling tools for the separation and recovery of radioisotopic gases in off-gas streams of nuclear fuel reprocessing. Single-layer adsorption experiments were performed to obtain both iodine and water adsorption data with AgoZ using continuous-flow adsorption systems. The commercial AgZ (IONEX-type Ag-900) used in this study was reduced to AgoZ in 4% H2/Argon at optimal conditions (400oC, 24 hours) determined in this study. The conditions for iodine adsorption experiments are: temperatures 100–200°C; iodine gas concentrations 1-50 ppmv; and dew points -65 to 20 oC. The sorbents are pre-equilibrated in the gas stream with a desired dew point prior to iodine adsorption to study the effect of dew points on the iodine adsorption capacity of AgoZ. The conditions for water adsorption experiments are: temperatures 100–200 °C and dew points -65 to 20 oC.
The effect of reduction conditions on the capacity of AgoZ was studied. The results confirmed the favorable effect of temperature and reduction time on the capacity of AgoZ, and suggested optimal reduction conditions: 400oC, 24 hours. Preliminary results of adsorption experiments indicated that the AgoZ had an iodine loading capacity of ~13 wt%, corresponding to a silver utilization of ~90%. Both the adsorption/desorption and equilibrium data indicated that iodine adsorption on AgoZ was mostly chemisorption. About 2.4 to 4.7% of the adsorbed iodine was physisorbed. Kinetic data were analyzed with the Shrinking Core model and Linear Driving Force model to determine the intraparticle mass transfer and reaction parameters. Single-component adsorption equilibrium data of iodine and water were also obtained to determine the saturation capacity and evaluate the parameters of isotherm models for modeling of co-adsorption.
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