Estimation of radon adsorption coefficients for coconut shell based activated charcoal system for radon and thoron removal applications

One of the simple and effective methods of removing 222Rn and 220Rn in the occupational domain of uranium mills and thorium processing facilities is based on the adsorption on activated carbon, which is easily available in India. However, for the large scale use of charcoal, it is necessary to study its 222Rn and 220Rn adsorption characteristics. Interestingly, adsorption coefficient (K) of various types of charcoal materials have been found to vary by a factor of more than ten depending upon the type of charcoal, environmental and experimental conditions. Adsorption coefficient plays a central role in determining the breakthrough time, which is the time after which a stable gas or a long lived species such as 222Rn, emerges at the downstream end of the adsorber system. The paper is aimed at generation of 222Rn breakthrough curves and estimation of breakthrough time (τ) for activated charcoal adsorption beds of different dimensions, and estimation of K values from the breakthrough curves, and evaluation of the dependence of K values with the flow rate of the carrier gas and pressure across the adsorber bed