Caractérisation et valorisation de bioressources végétales pour le prétraitement d'effluents par coagulation-floculation

Abstract : Biofloculants represent a sustainable alternative to metal salts and to synthetic polymers for water treatment by coagulation flocculation (CF). The optimal parameters of biomatrerials applicated in CF were mainly described by literature data. Opuntia ficus indica, known for its flocculating properties and olive mill waste (OMW), which its reuse not deeply examined, were chosen in our study. A methodology was proposed in order to determine the nature of the active molecules and to better understand the involving mechanism in CF. The experiment was conducted on a synthetic water based on kaolinite. The optimal conditions of CF were determined by jar test coupled with zeta potential and microscopy. For OMW, the optimum conditions are obtained for a pH of 11 and an extract dose of 62.5 mg L-1. The removal of OMW colors requires the use of 50 mg L-1 of a metal coagulant (Al2 (SO4)3). Afterwards, our study was based on a comparative approach of different water-soluble fractions as function of pH. The active molecules showed a maximum solubility at the optimal pH of CF, in both cases. The characterization of the raw materials by pKa, colorimetric assays (proteins, sugars, polyphenols and tannins) and the infrared analysis allowed to determine the molecules involved in CF (In both cases, tannins / flavonoids and sugars). CF experiments performed after enzymatic approach confirm the identification of molecules involved in the mechanism and suggest that the two materials operate through an adsorption and bridging mechanism. The efficiency of wastewater treatment (textile industry, landfill leachate) by Opuntia ficus indica extracts has been validated. Tannins/ flavonoids and especially quercetin for cactus promotes a colloidal material destabilization (coagulant) through anion exchanges and bridges; otherwise, the starch (cactus) or cellulose (OMW) forms a large cross-linked polymeric network responsible for bridging.
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Omar Bouaouine. Caractérisation et valorisation de bioressources végétales pour le prétraitement d'effluents par coagulation-floculation. Sciences de la Terre. Université de Limoges; Université Sidi Mohamed ben Abdellah (Fès, Maroc), 2018. Français. ⟨NNT : 2018LIMO0088⟩. ⟨tel-02320657v2⟩

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