The “conditioning cycles” are the number of cycles (often about five) that are required to achieve
a stable amount of adsorption and regeneration. Carbon, after undergoing the conditioning
cycles, is capable of adsorbing about 50% of the amount that was adsorbed by the virgin material.
Zeolite is capable of adsorbing about 90% of the amount adsorbed by the virgin material.
Polymers can vary over the range of 50% to 90%. This “conditioned isotherm” also defines the
“working capacity” of the adsorbent. The fact that carbon and some polymers will typically
desorb only 50% as much as the virgin material is thought to be caused by the continued
recapture of molecules (i.e., depressed vapor pressure) in the micro-pores. VOC can be removed
from these micro-pores only by pyrolysis, which would destroy the VOC, and either destroy the
polymer or alter the properties of the carbon.