Improving the Radon Adsorption Capacity of Activated Carbon by Liquid Nitrogen Modification

Abstract

Radon is a naturally occurring radioactive inert gas that poses a significant threat to the human health. Coconut shell activated carbon has been verified to be the best radon adsorbing material, but its radon adsorption capacity still cannot meet the requirement of industrial applications. Activated carbon modification using liquid nitrogen is an effective method for improving the radon adsorption capacity, but it is necessary to determine the conditions for large-scale production. In this study, the influence of environmental temperature, container geometry, and amount of activated carbon and liquid nitrogen on the modification effect are examined. The results show that the activated carbon has the best modification effect when the container is placed in a water bath at 50 °C. The container geometry and activated carbon mass have a minor influence on the modification effect. Further, the radon adsorption capacity is increased by 36% when 6.5 L of liquid nitrogen is added to 1 kg of activated carbon. The characterization results reveal that the chemical structure and elemental content of the activated carbon do not change after modification, but the number of micropores is significantly increased, especially the micropores with a size of 0.5-0.6 nm, which is related to the radon adsorption capacity of the modified activated carbon. Overall, the liquid-nitrogen-based modification is a simple, environment-friendly, and low-cost method to improve the radon adsorption capacity of activated carbon, which can be used in the large-scale production of highly efficient radon adsorbents.