Oxidation of trichloroethylene, toluene, and ethanol vapours by a partially saturated permeable reactive barrier

“The mitigation of volatile organic compound (VOC) vapors in the unsaturated zone largely
relies on the active removal of vapor by ventilation. In this study we considered an alternative
method involving the use of solid potassium permanganate to create a horizontal permeable
reactive barrier for oxidizing VOC vapors. Column experiments were carried out to investigate
the oxidation of trichloroethylene (TCE), toluene, and ethanol vapors using a partially
saturated mixture of potassium permanganate and sand grains. Results showed a significant
removal of VOC vapors due to the oxidation. We found that water saturation has a major effect
on the removal capacity of the permeable reactive layer. We observed a high removal
efficiency and reactivity of potassium permanganate for all target compounds at the highest
water saturation (Sw = 0.6). A change in pH within the reactive layer reduced oxidation rate
of VOCs. The use of carbonate minerals increased the reactivity of potassium permanganate
during the oxidation of TCE vapor by buffering the pH. Reactive transport of VOC vapors
diffusing through the permeable reactive layer was modeled, including the pH effect on the
oxidation rates. The model accurately described the observed breakthrough curve of TCE and
toluene vapors in the headspace of the column. However, miscibility of ethanol in water in
combination with produced water during oxidation made the modeling results less accurate
for ethanol. A linear relationship was found between total oxidized mass of VOC vapors per
unit volume of permeable reactive layer and initial water saturation. This behavior indicates
that pH changes control the overall reactivity and longevity of the permeable reactive layer
during oxidation of VOCs. The results suggest that field application of a horizontal permeable
reactive barrier can be a viable technology against upward migration of VOC vapors through
the unsaturated zone.”
© 2014 Elsevier B.V. All rights reserved.
(Citaat: Mahmoodlu, M.G., Hassanizadeh, S.M., Hartog, N. Raoof, A. Oxidation of trichloroethylene, toluene, and ethanol vapours by a partially saturated permeable reactive barrier – Journal of Contaminant Hydrology 164(2014) 193-208)