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Traitement des rejets sulfurés par passivation de surfaces : application à la prévention du drainage acide

Abstract : The aim of this work is to seek the inhibitors of the bacterial dissolution of sulfides and gangue minerais to slow or stop the undesirable chemical reactions during conservation of the mining wastes. Comparative tests of the passivation of the surface of sulfide minerais and waste of flotation were performed with using of conventional reagents (CaO, NaOH, phosphates, silanes, acetyl acetone, etc.) and original reagents for this purpose (alkyl dithiocarbamates). Leach tests of reference samples and samples treated with different reagents were carried out in percolation columns (68 weeks) and in stirred reactors (3 to 49 weeks). A single treatment with carbamate inhibits the bacterial oxidation of the pyrite and the other sulphides, and totally prevents the formation of acid waters (the stabilised pH was 5.3-5.8). Treatment of drainage water resulting from the heap makes it possible to obtaining a total precipitation of heavy metals: the residual concentrations of Fe, Cu and Zn are lower than 0,1 mg/l. The passivation of sulfides is the result of the formation wilh carbamate so much on the surface of the pyrite than in the solution, of organometallic compounds, which are stable in acidic medium. The adsorption layer formed leads to a considerable reduction in the hydratation rate of surface by avoiding the possible corrosion of the pyrite. Phosphates support the dissolution of aluminosilicates followed by a crystallization of kaolinite in the liquid phase. The results of the SEM and X-ray diffraction analyses of the sol id phase after 68 weeks of leaching showed that the surface of the treated pyrite was unaffected by the biodegradation process, whereas the control samples were considerably degraded.
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http://docnum.univ-lorraine.fr/prive/INPL_T_2000_FILIPPOVA_I_V.pdf
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Inna Vladimirovna Filippova. Traitement des rejets sulfurés par passivation de surfaces : application à la prévention du drainage acide. Sciences de la Terre. Institut National Polytechnique de Lorraine, 2000. Français. ⟨NNT : 2000INPL000N⟩. ⟨tel-01750481⟩

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