This work is a part of the OXYSOL project aiming at the conception of a global treatment pathway including In Situ Chemical Oxidation to clean up soils of former metallurgical sites.It deals with the selection of the most adapted oxidants. Batch experiments were performed with aged contaminated soil samples of a former steel-making plant to degrade the 16 US 1 EPA PAHs. In this research, hydrogen peroxide, modified Fenton's reaction, potassium permanganate, sodium percarbonate and sodium persulfate were compared at high and moderate doses. Hydrogen peroxide, modified Fenton's reagent, percarbonate and activated persulfate led to a maximum degradation ratio of 45%. A higher ratio (70%) was obtained with a high dose of permanganate. Except for permanganate, increasing oxidant dose did not improve degradation rates, especially with radical-based oxidative systems probably due to radical scavenging. Oxidant doses had an effect on pH that drastically increased or dropped in some cases, which was a drawback. Permanganate efficacy was mainly assigned to its persistence. In all cases, the low availability of PAHs, partly sequestrated in the aged soil, was identified as the most limiting factor for degradation performance. Oxidants were ranked according to their efficiency for PAH oxidation in soils. Efficiency was not correlated to the doses.
[1] Alteration and dissolution resulting from reactive fluid flows in vertical fracture are investigated from numerical and laboratory experiments. Due to fluid density contrast, buoyancy effects are observed leading to significant changes in fracture geometry. Buoyant and forced convection forces act here in the same direction. The experiments were carried out at two different flow rates. When buoyancy forces are preponderant (low injection flow rate), the dissolution rate increases with the vertical distance. By contrast, for convectiondominated transport (high injection flow rate), a uniform dissolution is observed. Using numerical simulations, four dissolution regimes were identified. The fracture patterns observed strongly depend on the characteristic dimensionless numbers of the process, respectively, the Richardson, Damköhler, and Péclet numbers. The good agreement between numerical simulations and experimental results in terms of fracture patterns highlights the capability of the numerical model to describe the complex coupling between flow dynamics, buoyancy, and chemical reaction. Finally, a 3-D behavior diagram is constructed to illustrate these interactions and as a means of relating the appropriate dimensionless parameters to the morphological changes observed.Citation: Olte´an, C., F. Golfier, and M. A. Bue`s (2013), Numerical and experimental investigation of buoyancy-driven dissolution in vertical fracture,
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