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L’acide phytique : réactif de précipitation bio-sourcé pour une hydrométallurgie verte

Abstract : Although many agro-resources reagents have already been studied for potential use in hydrometallurgy, very few have found industrial application. The possibility of using phytic acid as a selective precipitation reagent was investigated in this work. This acid, which is the main source of phosphorus present in cereals, is considered as an antinutritional agent, which is eliminated by simple water soaking. The precipitation of five metal cations (Al³⁺, Fe³⁺, Pb²⁺, Cu²⁺, and Zn²⁺) was studied, the first three metals being often considered undesirable in hydrometallurgy. First, the formulae of the metal phytates were established (Al₃C₆H9P₆O₂₄,7H₂O, Fe7C1₂H15P1₂O₄₈,15H₂O, Pb₆C₆H₆P₆O₂₄,10H₂O, Cu₆C₆H₆P₆O₂₄,8H₂O, Zn₆C₆H₆P₆O₂₄,6H₂O). Then, the solubility of these compounds was determined in water at 20°C to determine their solubility product and establish their conditional solubility diagram to consider two possible study cases: iron removal in calcine leachate (zinc hydrometallurgy) and removal of Fe³⁺, Al³⁺ and Pb²⁺ in nitric leachates from printed circuit board. These separations were optimized using design of experiment methodology. In both cases, only pH influences precipitation. In the case of the Iron/Zinc mixture, it is possible to remove more than 99,6 % of the trivalent iron with less than 0,6 % of the zinc co-precipitated. In the second case, a two-step precipitation allows to remove 100 % of the iron, 99 % of the aluminum, 98 % of lead with less than 2 % copper loss. Fe/Zn separation was studied at the pilot step. The results confirmed those obtained at the laboratory step. A comparison with the three main existing industrial processes demonstrated that phytic acid allowed to obtain better iron removal efficiency and reduced zinc in the precipitate, leading to solid waste with a less environmental impact than jarosite considered as hazardous waste.
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Submitted on : Friday, September 24, 2021 - 3:56:46 PM
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  • HAL Id : tel-03354081, version 1

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Julien Comel. L’acide phytique : réactif de précipitation bio-sourcé pour une hydrométallurgie verte. Chimie. Université de Lorraine, 2021. Français. ⟨NNT : 2021LORR0067⟩. ⟨tel-03354081⟩

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