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Chemosphere. 2019 Jun 4;233:667-676. doi: 10.1016/j.chemosphere.2019.05.295. [Epub ahead of print]

Comparative assessment of a foam-based oxidative treatment of hydrocarbon-contaminated unsaturated and anisotropic soils.

Author information

1
Université de Bourgogne Franche-Comté - Besançon, Institut UTINAM - UMR CNRS 6213, 16, Route de Gray, 25030, Besançon, France.
2
Université de Bourgogne Franche-Comté - Besançon, Institut UTINAM - UMR CNRS 6213, 16, Route de Gray, 25030, Besançon, France. Electronic address: nicolas.fatin-rouge@univ-fcomte.fr.

Abstract

In situ delivery of liquid reagents in vadose zone is limited by soil anisotropy and gravity. The enhanced delivery of persulfate (PS) as oxidant, using a new foam-based method (F-PS) was compared at bench-scale to traditional water-based (W-PS) and surfactant solution-based (S-PS) deliveries. The goal was to distribute PS uniformly in coal tar-contaminated unsaturated and anisotropic soils, both in terms of permeability and contamination. Water was the less efficiently delivered fluid because of the hydrophobicity of the contaminated soils. Surfactant enhanced PS-distribution into contaminated zones by reducing interfacial tension and inverting soil wettability. Regardless of coal tar contamination contrasts (0 vs. 5 and 1 vs. 10 g kg soil-1) or strong permeability contrasts, PS-solution injection after foam injection led to the most uniform reagents delivery. While PS-concentration varied more than 5-times between zones using W-PS and S-PS methods, it varied less than 1.6-times when the F-PS one was used. Finally, despite unfavorable conditions, the foam-based method did not show any detrimental effect regarding the oxidation of hydrocarbons compared to the W-PS and S-PS methods carried out in ideal conditions. Moreover, hydrocarbon degradation rates were slightly higher when using F-PS than S-PS due to a lower surfactant content in the targeted zone.

KEYWORDS:

Coal tar contamination; ISCO; Soil anisotropy; Surfactant foam; Vadose zone

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