  The noble elements, argon and xenon, are frequently employed as the target
and event detector for weakly interacting particles such as neutrinos and Dark
Matter. For such rare processes, background radiation must be carefully
minimized. Radon provides one of the most significant contaminants since it is
an inevitable product of trace amounts of natural uranium. To design a
purification system for reducing such contamination, the adsorption
characteristics of radon in nitrogen, argon, and xenon carrier gases on various
types of charcoals with different adsorbing properties and intrinsic
radioactive purities have been studied in the temperature range of 190-295 K at
flow rates of 0.5 and 2 standard liters per minute. Essential performance
parameters for the various charcoals include the average breakthrough times
($\tau$), dynamic adsorption coefficients (k$_a$) and the number of theoretical
stages (n). It is shown that the k$_a$-values for radon in nitrogen, argon, and
xenon increase as the temperature of the charcoal traps decreases, and that
they are significantly larger in nitrogen and argon than in xenon gas due to
adsorption saturation effects. It is found that, unlike in xenon, the dynamic
adsorption coefficients for radon in nitrogen and argon strictly obey the
Arrhenius law. The experimental results strongly indicate that nitric acid
etched Saratech is the best candidate among all used charcoal brands. It allows
reducing total radon concentration in the LZ liquid Xe detector to meet the
ultimate goal in the search for Dark Matter.
