Synthèse, caractérisation et réactivité vis-à-vis du chrome (VI) de la mackinawite (FeS)

Abstract : This study is about the synthesis, the characterisation of an iron sulphide, mackinawite (FeS) and the reactivity with a metallic pollutant, chromium (VI). First of all, the synthesis of mackinawite was driven from two ways of synthesis currently reported in the literature and which involve the addition of a sulphur (-II) solution to a solution containing iron (0) or iron (II). The characterisation of the physical chemistry properties has shown that the crystallinity of the products obtained from the two ways of synthesis are not equivalent: the product obtained from iron (II) is poorly crystallised whereas the one synthesised from metallic iron is well crystallised and identical to natural mackinawite. The second way of synthesis has then been retained for this study. Otherwise, the alteration of the physical chemistry properties of the surface of mackinawite has been underlined, with the presence of both Fe(II) and Fe(III) bonded to sulphur. At last, the oxidation study has been complex, due to the simultaneous presence of several oxidation products which are greigite, elemental sulphur and iron (oxyhydr)oxides, magnetite and eventually goethite. Elemental sulphur and iron (oxyhydr)oxides are the final products of the reaction, from which a mechanism of mackinawite oxidation has been proposed. The second part of this work concerns the study of the mackinawite/chromium (VI) reactivity and has demonstrated the ability of mackinawite to remove chromium (VI) from solution. The elimination of chromium (VI) results from an oxidoreduction mechanism in solution, chromium (VI) interacting with iron (II) and sulphur species arising from the mackinawite dissolution. The structural analysis of the reaction products reveals the presence of residual mackinawite, greigite, goethite, elemental sulphur and a phase including iron, oxygen and chromium. A reaction mechanism of chromium (VI) reduction by mackinawite has been proposed. It seems that the precipitation of the reaction products is the limiting factor in the chromium (VI) reduction by mackinawite.
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Sophie Boursiquot-Michel. Synthèse, caractérisation et réactivité vis-à-vis du chrome (VI) de la mackinawite (FeS). Autre. Université Henri Poincaré - Nancy 1, 2002. Français. ⟨NNT : 2002NAN10236⟩. ⟨tel-01754439⟩

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