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Déferrisation des eaux par procédé d’électrocoagulation : étude des phénomènes physico-chimiques et réactionnels impliqués

Abstract : Water scarcity in some areas requires the exploitation of some ferruginous sources. However, the presence of Fe(II) induces aesthetic and organoleptic problems. The electrocoagulation (EC), as an alternative process of the conventional method, proved its efficacy for iron removal. Nevertheless, the iron removal mechanism in EC process remains unstudied and still unclear. The simultaneous involvement of several phenomena makes difficulties to study the system. This thesis aims to provide a better understanding of the mechanism of Fe(II) removal by EC and to highlight the phenomena that are most likely. Thus, different methods of iron removal and liquid and solid analysis techniques have been used. By means of a forced recirculating unit, EC's technique with aluminum electrodes reduce the dissolved iron of 25 mg Fe(II)/L - solution by about 97% with an optimum energy amount of 0,21 kWh/m3. Anoxic experiments showed that the reduction of ionic iron by adsorption on Al(OH)3 flocs is negligible (18%). Oxidation-precipitation experiments showed that at work pH 6,5, Al(OH)3 catalyzes the oxidation reaction. The catalytic effect is more pronounced in the presence of chloride ions than in sulfate ions. Fe(II)-speciation associated with kinetic modeling have allowed to explain of the mode by which these ions acts on the oxidation reaction kinetics. However, EC experiments in anoxic and oxygenated media show that the proportion of oxidation in iron removal is insignificant for work pH. Thermodynamic calculations allowed to propose the precipitation of Fe(OH)2 in the vicinity of the cathode as the predominant mechanism of iron removal by EC. The presence of carbonates affects the performance of the process by reducing the precipitation of Fe(OH)2; this was attributed to the decrease of the local pH and the free Fe(II) amount by Fe(II)-complexes formation
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Submitted on : Tuesday, October 12, 2021 - 11:44:41 AM
Last modification on : Wednesday, November 3, 2021 - 7:09:38 AM
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Amira Doggaz. Déferrisation des eaux par procédé d’électrocoagulation : étude des phénomènes physico-chimiques et réactionnels impliqués. Génie des procédés. Université de Lorraine; Université de Carthage (Tunisie), 2018. Français. ⟨NNT : 2018LORR0171⟩. ⟨tel-01963699⟩



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