Oxidant selection to treat an aged PAH contaminated soil by in situ chemical oxidation.

International audienceThis 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 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

Ennoyage des mines de fer lorraines : impact sur la qualité de l'eau

International audienceThe flooding of the abandoned ironmines of Lorraine leads to a degradation of the groundwater quality. Laboratory experiments allowed us to build a kinetic chemical model based on simple chemical mechanisms. During mining operations, pyrite oxidation and carbonate dissolution lead to the precipitation of gypsum. The local decrease of pH favours local dissolutions of minerals and releases ions that are fixed on cationic exchange sites. During the flooding of the mine workings, the dissolution of the newly precipitated gypsum, the precipitation of carbonates and cationic exchange reactions are responsible for the increase of the concentrations of sulphate, magnesium, sodium, potassium and strontium in water. Thereafter, these concentrations would decrease with the natural leaching of the mining reservoir.L’ennoyage des mines de fer abandonnées de Lorraine entraîne une dégradation de la qualité de l’eau souterraine. Des expériences en laboratoire ont permis la construction d’un modèle chimique cinétique, basé sur des schémas réactionnels simples. Lors de l’exploitation, l’oxydation de la pyrite et la dissolution des carbonates conduisent à la précipitation de gypse. Les baisses locales de pH favorisent des dissolutions ponctuelles de minéraux et libèrent des ions qui se fixent sur des sites d’échanges cationiques. Lors de l’ennoyage, la dissolution du gypse néoformé, la précipitation des carbonates et des réactions d’échanges cationiques entraînent une hausse des concentrations de l’eau en sulfate, magnésium, sodium, potassium et strontium qui devraient ensuite diminuer au fur et à mesure du lessivage naturel du réservoir

Identification of particles transport regimes in closed channel flow at low Reynolds numbers

International audienceIdentification of particles transport regimes in closed channel flow at low Reynolds number

A comparative study of five boundary treatment schemes for stationary complex boundaries in the lattice Boltzmann method

International audienceA comparative study of five boundary treatment schemes for stationary complex boundaries in the lattice Boltzmann metho

Effects of the geometry of two-dimensional fractures on their hydraulic aperture and on the validity of the local cubic law

International audienc