Continuous cryogenic adsorption adjustments of radon in air using carbon-based microporous adsorbents
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In underground low-background laboratories (LRBL), minimizing radon concentration is crucial. This study developed a cryogenic Rn adsorption system, which operated for more than 5 h at a flow rate of 60 L/min. The dynamic adsorption coefficients (Kd) of Rn on four carbon-based adsorbents were measured at 293 K, 243 K and 223 K. Combined with the results of N2-adsorption and desorption,XPS, FTIR and SEM test results indicated that the larger the micropore volume within the 0.5–0.7 nm range, the higher the the Kd of Rn adsorption of the adsorbent, and this difference becomes more obvious with the decrease of adsorption temperature. CarbosieveSIII exhibited the highest Kd at 223 K (436 L/g). Adsorption penetration curves of each component of Rncontaining air on activated carbon were measured using an infrared gas analyzer and a RAD7 radon meter. The CO2 concentration gradient was adjusted, and the Kd of all adsorbents (including reduced carbon molecular sieves) were measured. Experimental results revealed that CO2 acts as the dominant competitive adsorbate for radon capture when water vapor interference was eliminated.
Abstract
In underground low-background laboratories (LRBL), minimizing radon concentration is crucial. This study developed a cryogenic Rn adsorption system, which operated for more than 5 h at a flow rate of 60 L/min. The dynamic adsorption coefficients (Kd) of Rn on four carbon-based adsorbents were measured at 293 K, 243 K and 223 K. Combined with the results of N2-adsorption and desorption,XPS, FTIR and SEM test results indicated that the larger the micropore volume within the 0.5–0.7 nm range, the higher the the Kd of Rn adsorption of the adsorbent, and this difference becomes more obvious with the decrease of adsorption temperature. CarbosieveSIII exhibited the highest Kd at 223 K (436 L/g). Adsorption penetration curves of each component of Rncontaining air on activated carbon were measured using an infrared gas analyzer and a RAD7 radon meter. The CO2 concentration gradient was adjusted, and the Kd of all adsorbents (including reduced carbon molecular sieves) were measured. Experimental results revealed that CO2 acts as the dominant competitive adsorbate for radon capture when water vapor interference was eliminated.