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Réactivité argiles-polluants métalliques : simulation des barrières argileuses des sites de stockage des déchets

Abstract : Storage of household and industrial wastes has become an important issue for the environment. Smectites, with a low permeability and a high capacity to retain pollutants, are frequently used as an engineered barrier at the bottom of landfills. The aim of this work was to simulate in the laboratory the infiltration of metallic pollutants solutions in smectites, to analyze the interaction mechanisms and to predict the hydraulic and physico-chemical behavior of these clays. Natural reference smectites (SWy2 exchanged with different cations, Na+ and Ca2+) but also a synthetic smectite were used together with metallic pollutant solutions (containing mainly Zn and Pb). Several parameters were tested in the "batch" experiments: solid/liquid ratio, pollutant concentration, pH ... Analyses of leachates showed that the sodic clay better adsorbs pollutants than the calcic clay, and the adsorption was better in the neutral medium than in acidic conditions (pH 5). The experimental results were then modeled using the PHREEQC code and the 2SPNE model. From the exchange and complexation constants of the literature, simulations showed that the model was in very good agreement with the experimental data for zinc. These results allowed to establish new thermodynamic constants for lead and to assess the adsorption mechanisms as a function of the equilibrium concentration of the metallic solution and the pH. To simulate a clay barrier at the laboratory scale, infiltration experiments under pressure were performed onto smectites within oedometer cells. Whether with deionised water, metallic pollutant solutions (Cu, Pb, Zn) or a synthetic leachate, at free pH or buffered at 5, these clays kept a hydraulic conductivity less than 10-12 ms-1 which proved their good sealing properties.
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Mariem Ghayaza. Réactivité argiles-polluants métalliques : simulation des barrières argileuses des sites de stockage des déchets. Sciences de la Terre. Université d'Orléans, 2012. Français. ⟨NNT : 2012ORLE2009⟩. ⟨tel-00716445v2⟩

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