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Transport and sorption of toxic volatile organic compounds
(VOCs) to several commercial adsorbents were investigated in
this study. Benzene, toluene andtrichloroethylene were selected
as representative adsorbates as each is highlytoxic and is
commonly found in the environment.
To mimic the environmental conditions, such as indoor air and
soil gas, the concentrations of these VOCs were set at around
5 to 200 ppm. Three differentcommercial adsorbents, including
activated carbon, zeolite, and polymer were chosen as
representative adsorbents. A differential adsorption bed (DAB)
system was employed to determine both the adsorption/desorption
kinetics and equilibrium of the VOCs to the adsorbents. The
Freundlich isotherm was found to well describe the sorption
equilibrium of the three VOCs onto all the adsorbents tested.
At the same relative pressure of the three VOCs,
adsorptioncapacities in terms of molecule number were found to
be almost the same for allthe three VOCs on GAC, indicating that
the affinity between GAC and three VOCsare very similar. The
model simulations were found to fit very well to the high
concentration experimental kinetic data for both adsorption and
desorptionusing two adjust parameter, effective diffusivity, and
the Freundlich isothermexponent. The extracted model parameter,
effective diffusivity and n, were then used to predict the
experimental kinetic data for the same adsorbent/adsorbate
combination at other concentrations. Model predictions were
found tobe very close to the observed experimental data,
indicating that the model is very appropriate for the systems
tested. Finally, the tortuosity factors extracted for all the
three adsorbents were found to fall in the range of 7 to 9
suggested in the literature, further substantiating the
applicability of the model.
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