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Intensification de la dégradation de polluants organiques par photocatalyse dans des émulsions de Pickering

Abstract : This thesis examines a promising new method for the effective depollution of water contaminated by insoluble organic pollutants such as toluene, 1-methylnaphthalene, nitrobenzene, etc. This advanced oxidation method is based on heterogeneous photocatalysis in Pickering emulsions. In this type of emulsion, the stabilizing surfactants of the oily droplets are replaced by solid nanoparticles having high photocatalytic properties. Moreover, these solid nanoparticles must fulfill the conditions of partial wettability in both aqueous and oily phases thanks to a hydrophilic-hydrophobic balance on their surface. For this reason, the titanium dioxide (TiO2) anatase was prepared by the sol-gel method and then modified by fluorination to obtain the TiO2-F catalyst. The objective is to formulate Pickering oil-in-water (O/W) emulsions from organic pollutants of low water solubility. The synthesized catalysts were characterized by XRD, BET, SEM, DRS, XPS, and TG-TD-MS. It has been shown that fluorination brings about important changes in the optical properties of TiO2 (change in band gap) and improves the hydrophilic / hydrophobic balance at its surface significantly. Moreover, the obtained results indicate that stable Pickering emulsions can be formulated using TiO2 or TiO2-F nanoparticles. The type and stability of the emulsions depend on the wettability of the stabilizing nanoparticles evaluated by contact angle measurements. The wettability of the nanoparticles has been found to be highly dependent on the type of oil due to the contributions of polarity and specific interactions with pollutants. The study of Pickering emulsions by electrical conductivity, optical microscopy and light scattering showed that high stability was obtained under partial wetting conditions: contact angle in water between 70 and 110°. The change in the size of the oil droplets with the oil/photocatalyst mass ratio confirmed a strong adsorption of the catalyst nanoparticles on the oil droplets. Finally, the judged stable emulsions were photodegraded under UV radiation. The photodegradation kinetics of organic pollutants measured by HPLC showed that degradation was intensified using Pickering emulsions compared to non-emulsified systems. These results have shown that the use of Pickering emulsions stabilized by titanium dioxide nanoparticles is an effective and innovative way to intensify the photocatalytic degradation of organic pollutants
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Nidhal Fessi. Intensification de la dégradation de polluants organiques par photocatalyse dans des émulsions de Pickering. Chimie organique. Université de Lyon; Université de Gabès (Tunisie), 2018. Français. ⟨NNT : 2018LYSE1352⟩. ⟨tel-02068199⟩

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