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Précipitation des gels de silice en solution aqueuse sursaturée à forte acidité : mécanismes et mésostructures, application à la filtrabilité des pulpes dans les procédés hydrométallurgiques

Abstract : The formation of silica gels in hydrometallurgical processes is very often problematic for the performance of the solid-liquid separation steps, due to clogging of the filters. These steps are carried out downstream of leaching aiming to solubilize the elements of interests, in particular in solutions with strong acidity. Also dissolved during acidic leaching, the silicon then precipitates in the form of silicon oxide and forms gels extremely detrimental to filtration. In collaboration with ERAMET Research, a research center of ERAMET, a french mining group that designs hydrometallurgical processes, we studied the influence of the leaching conditions of a specific ore on the dissolution kinetics of silicon as well as on the mechanisms of precipitation of silica in an acidic solution. We have shown that below a pH value of 2, silica polymerizes to form gels following mechanisms independent of the ionic composition of the solution. Based, on the structural study of the gels, carried out by small angle radiation scattering (SAXS) we proposed a model for the mesotructure, which explain the impact on filtration rates. Subsequently, strategies to modify the mesostructure of the gels by physical or physicochemical approaches were considered. The results have shown the potentialities of these strategies in the short term to improve the filterability of precipitated silica gels in a hydrométallurgical process.
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https://tel.archives-ouvertes.fr/tel-01925392
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Submitted on : Friday, November 16, 2018 - 4:20:07 PM
Last modification on : Saturday, August 15, 2020 - 4:33:01 AM
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  • HAL Id : tel-01925392, version 1

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Christian Manfoumbi. Précipitation des gels de silice en solution aqueuse sursaturée à forte acidité : mécanismes et mésostructures, application à la filtrabilité des pulpes dans les procédés hydrométallurgiques. Génie des procédés. Université Paul Sabatier - Toulouse III, 2017. Français. ⟨NNT : 2017TOU30251⟩. ⟨tel-01925392⟩

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