Adsorption Equilibria of Krypton, Xenon, Nitrogen and Their Mixtures on Molecular Sieve 5A and Activated Charcoal

Abstract

The adsorption equilibria of Kr, Xe and N₂, which are constituents of the off-gas from nuclear reprocessing processes, on representative adsorbents (Molecular Sieve 5A (MS5A) and activated charcoal) were studied. Adsorption experiments were conducted in the temperature range of 77 to 323 K using a packed bed column. The adsorption isotherms for the activated charcoal adsorbent were successfully correlated by the vacancy-solution model. The adsorption isotherms for the MS5A adsorbent were properly correlated by the Langmuir model and the vacancy solution model. The adsorption experiments for the binary component systems (Kr—Xe, Kr—N₂ systems) were also performed, and the results suggest that the coexistence of Xe greatly inhibits the adsorption of Kr. The coexistence of large amounts of N₂ was also found to inhibit the adsorption of Kr. The experimental results for the adsorption equilibrium of binary component systems on the activated charcoal adsorbent were well reproduced by the vacancy solution model without parameter fitting. The binary adsorption equilibrium on the MS5A adsorbent is rather well predicted by the ideal adsorbed solution model without parameter fitting. The use of the vacancy solution model for this adsorption system requires the optimization of parameters, but the binary adsorption equilibrium is well reproduced with the optimized parameters.

KEYWORDS:

• nuclear reprocessing
• adsorption
• adsorption isotherms
• krypton
• xenon
• nitrogen
• molecular sieve
• activated charcoal
• mixture gas
• vacancy solution model