Nabil Tabaja

Cette thèse a été réalisée dans le cadre d’une cotutelle de thèse (3 ans) Franco-Libanaise entre l’Université Pierre et Marie Curie de Paris et l’Université Libanaise de Beyrouth. Nabil Tabaja a été entièrement financé par le Groupe de Recherche MAPE (Nanosized Porous Materials, Preparation, Advanced Characterization and Environmental Applications) de Beyrouth que nous tenons à remercier. Le but de ce travail était de tester et de valoriser des catalyseurs à base d’oxydes de fer et de ferrites pour la dépollution des eaux par photocatalyse sous lumière visible puis solaire. Les catalyseurs étudiés ont été préparés en employant des silices poreuses en tant que gabarits pour obtenir majoritairement : soit des nanoparticules, NP, d’oxydes de fer ayant cristallisé à l’intérieur des pores des silices (INTERNES, répliquées), soit des nanoparticules ayant cristallisé à l’extérieur des grains de silice et formées lors des traitements d’activation thermiques (EXTERNES). Nous avons employées des techniques faciles à transférer pour obtenir les silices (Chapitre 1). Notre objectif à ce niveau était d’obtenir plus de 50g d’au moins six silices ayant des diamètres de mésopores différents. La variation de ces diamètres s’accompagne de modifications des connections entre les mésopores principaux et des propriétés des surfaces des silices. Différents sels précurseurs de fer (chlorure, nitrate) ou des mélanges de métaux ont été déposées sur les différentes silices obtenues par des techniques de dépôt de type deux solvants (2S). Les échantillons ont été traités thermiquement à 700°C sous air pour obtenir des nanoparticules d’oxydes (Chapitre 2). Nous montrons que, si le diamètre des NP nanorépliquées est en général proche du diamètre des pores des silices initiales, les formes et la dispersion des nanoparticules internes dans les grains de silice dépendent de différents facteurs expérimentaux, des sels précurseurs, des solvants et du type de silice sélectionnée. Nous montrons également que la formation des particules externes est associée au traitement thermique imposé et peut être favorisée en choisissant le bon solvant et le bon sel précurseur pour une silice déterminée. Des premiers tests ayant démontrés un taux de lixiviation important dans le cas de catalyseur au fer, nous avons testé des ferrites de différentes compositions (cations (II) de différentes électronégativités, Ni(II), Co(II), Cd(II), Zn(II) ; cation (III), Cr(III)). Afin de comparer la réactivité catalytique des catalyseurs, deux types de réactions sont introduites successivement. Le premier type de réaction, l’oxydation photocatalytique du méthanol et du formaldéhyde, a été employé à titre fondamental. Dans ce cas, notre objectif était d’étudier la sélectivité de la réaction et d’identifier de façon inambigue quelles nanoparticules présentes dans la formulation des catalyseurs permettent, partant d’une espèce à un seul carbone, d’obtenir des produits à 2 ou plus atomes de carbone (Chapitre III). La seconde réaction, l’oxydation photocatalytique d’un pesticide, a été employée pour démontrer que les catalyseurs peuvent être utiles à titre appliqué. Le pesticide sélectionné a été le carbendazime (Chapitre IV) dont nous avons suivi la décomposition. Ces études n’ont été possibles que grâce à l’emploi de techniques de caractérisation avancées, de type TOC et GC-MS. Les meilleures activités catalytiques ont été analysées en fonction de la présence d’une majorité de NP internes et/ou externes et d’autres espèces plus dispersées et non visibles par DRX.

The development of efficient catalysts for advanced oxidation processes is of major importance for the removal of organic contaminants from water and industrial effluents. In this context, this work investigates the preparation, structural characterization, and catalytic performance of Fe-loaded SBA-15 mesostructured silica materials. SBA-15 silicas were synthesized under different preparation and calcination conditions and subsequently used as supports for the deposition of iron species, followed by controlled calcination to obtain Fe-containing catalysts.The physicochemical properties of the Fe-loaded materials were characterized using complementary techniques. X-ray diffraction and nitrogen adsorption–desorption measurements were used to determine the crystalline phases and textural properties of the materials. Microscopic analyses by scanning and transmission electron microscopy combined with energy-dispersive spectroscopy provided information on the size, morphology, and spatial distribution of iron oxide nanoparticles located either inside the mesopores or on the external surface of silica grains. UV–visible spectroscopy and Tauc plot analysis were employed to investigate the optical and semiconducting properties of the iron oxide nanoparticles.The Fe-loaded samples calcined at 700 °C contain hematite nanoparticles together with dispersed iron species and iron-containing colloidal phases. Their catalytic activity was evaluated through methanol oxidation in aqueous solution under air in the presence of hydrogen peroxide. Formaldehyde was identified as the main reaction product, followed by methyl formate and ultimately carbon dioxide. The catalytic activity strongly depends on the structural and electronic properties of the iron oxide nanoparticles, particularly their size, dispersion, and semiconducting behavior, providing insight into structure–reactivity relationships governing iron-oxide-based photocatalysts for advanced oxidation processes.

In this study, chromium ferrite (FeCr; CrFe₂O₄) nanoparticles supported on activated carbon (AC), obtained from agricultural olive mill solid waste, were synthesized via a simple hydrothermal process. The structural, morphological, optical, and chemical properties of the FeCr/AC composite were characterized using XRD, SEM, EDX, DRS, BET, and FTIR techniques. The FeCr/AC composite was applied as a heterogeneous photo-Fenton catalyst for the degradation of methylene blue (MB) dye in an aqueous solution under 25 W visible-light LED irradiation. Critical operational factors, such as FeCr/AC dosage, pH, MB concentration, and H₂O₂ levels, were optimized. Under optimal conditions, 97.56% of MB was removed within 120 min of visible-light exposure, following pseudo-first-order kinetics. The composite also exhibited high efficiency in degrading methyl orange dye (95%) and tetracycline antibiotic (88%) within 180 min, with corresponding first-order rate constants of 0.0225 min⁻¹ and 0.0115 min⁻¹, respectively. This study highlights the potential of FeCr/AC for treating water contaminated with dyes and pharmaceuticals, in line with the Sustainable Development Goals (SDGs) for water purification.

In this study, chromium ferrite (FeCr; CrFe₂O₄) nanoparticles supported on activated carbon (AC), obtained from agricultural olive mill solid waste, were synthesized via a simple hydrothermal process. The structural, morphological, optical, and chemical properties of the FeCr/AC composite were characterized using XRD, SEM, EDX, DRS, BET, and FTIR techniques. The FeCr/AC composite was applied as a heterogeneous photo-Fenton catalyst for the degradation of methylene blue (MB) dye in aqueous solution under 25 W visible light LED irradiation. Critical operational factors such as FeCr/AC dosage, pH, MB concentration, and H₂O₂ levels were optimized. Under optimal conditions, 97.56% of MB was removed within 120 minutes of visible light exposure, following pseudo-first-order kinetics. The composite also exhibited high efficiency in degrading methyl orange dye (95%) and tetracycline antibiotic (88%) within 180 minutes, with corresponding first-order rate constants of 0.0225 min⁻¹ and 0.0115 min⁻¹, respectively. This study highlights the potential of FeCr/AC for treating water contaminated with dyes and pharmaceuticals, in line with the Sustainable Development Goals (SDGs) for water purification.

Ensuring effective water purification is essential for addressing freshwater scarcity and achieving the United Nations Sustainable Development Goals (SDGs). An efficient hybrid mixture, composed of FeCr quantum dots doped into mesoporous silica SBA-15 support and activated carbon (AC) derived from olive mill solid wastes, has been developed for treating high optical density polluted aqueous environments. This hybrid, denoted as FeCr-SBA-15/AC, was examined for its efficacy in the adsorption and photo-Fenton degradation of met orange dye (MO), a model high-optical-density pollutant, under visible light exposure. Characterization of the prepared samples was conducted using X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), Brunauer–Emmett–Teller (BET) surface area analysis, diffuse reflectance spectroscopy (DRS), scanning electron microscopy (SEM), and transmission electron microscopy (TEM). Key parameters investigated included catalyst dosage, dye concentration, solution pH, and H₂O₂ concentration. Remarkably, the FeCr-SBA-15/AC hybrid exhibited superior photocatalytic activity, achieving a degradation efficiency of 97% for MO under optimized conditions (catalyst dosage = 0.75 g L⁻¹, dye concentration = 20 mg L⁻¹, pH = 5.47, and 0.5 mL H₂O₂) after 180 min of irradiation with visible light. This performance surpassed that of FeCr-SBA-15 alone by 20%, due to the synergistic effects of adsorption and photo-Fenton. The adsorption of MO onto AC followed the Freundlich model equilibrium isotherm, while the experimental data for the hybrid mixture aligned well with the pseudo-first-order Langmuir–Hinshelwood kinetic model with a rate constant of 0.0173 min⁻¹. The leaching of Cr in the solution was very low—0.1 ppm—which is below the detection limit. These findings underscore the potential of the synthesized FeCr-SBA-15/AC hybrid as a cost-effective, environmentally friendly, and highly efficient photo-Fenton catalyst for treating wastewater contaminated by industrial effluents.

Industrial wastewater discharge, tainted with hazardous substances, including dyes like methylene blue (MB) from the textile sector, further emphasizes the need for water treatment to produce safe drinking water. This study explores the potential of olive mill solid waste, an abundant and cost-effective agricultural waste in Mediterranean regions, to yield high-quality activated carbon (AC) with zinc chloride activation for MB adsorption. The activation process, carried out at a modest temperature of 500 °C without the need for an inert atmosphere, resulted in AC with remarkable characteristics, boasting a substantial surface area of 1184 cm²·g⁻¹ and a total pore volume of 0.824 cm³·g⁻¹. Extensive characterization of the AC was carried out through a large range of surface techniques. The pH of the solution had minimal influence on MB adsorption, the maximum removal was 95%, which was under slightly acidic pH conditions (5.8), and the adsorbent dose was 0.4 g·L⁻¹ for a 50 mg·L⁻¹ MB concentration. Equilibrium data pertaining to MB adsorption were subjected to fitting with different models, namely Langmuir, Freundlich, and Temkin. Notably, the Langmuir model exhibited the best fit, revealing a maximum monolayer adsorption capacity of 500 mg·g⁻¹ at 25 °C, and the adsorption kinetics closely followed a pseudo-second-order model.

Ensuring access to affordable water treatment systems is paramount, given the dire situation where millions are deprived of clean drinking water. Industrial wastewater discharge, tainted with hazardous substances, including dyes like methylene blue (MB) from the textile sector, further emphasizes the need for water treatment to produce safe drinking water. This study explores the potential of Olive Mill Solid Waste (OMSW), an abundant and cost-effective agricultural waste in Mediterranean regions, to yield high-quality activated carbon (AC) with zinc chloride (ZnCl₂) activation for MB adsorption. The activation process, carried out at a modest temperature of 500°C without the need for an inert atmosphere, resulted in AC with remarkable characteristics, boasting a substantial surface area of 1,184 cm².g^− 1 and a total pore volume of 0.824 cm³.g^− 1. Extensive characterization of the AC was carried out through diverse techniques; Fourier Transform Infrared Spectroscopy (FT-IR), X-Ray Diffractometry (XRD), Brunauer, Emmett and Teller (BET) analysis, Zeta potential, Scanning Electron Microscopy (SEM), and Energy Dispersive X-ray (EDX) spectroscopy. The adsorption performance of the prepared AC was thoroughly evaluated through a comprehensive examination of various factors, including initial dye concentration, contact time, adsorbent dosage, and solution pH. The pH of the solution had minimal influence on MB adsorption, the maximum removal was 95% which was under slightly acidic pH conditions (5.8) and with an adsorbent dose of 0.4 g.L^− 1 for a 50 mg.L^− 1 MB concentration. Equilibrium data pertaining to MB adsorption were subjected to fitting with different models, namely Langmuir, Freundlich, and Temkin. Notably, the Langmuir model exhibited the best fit, revealing a maximum monolayer adsorption capacity of 500 mg.g^− 1 at 25°C, and the adsorption kinetics closely followed a pseudo-second order model. These experimental results underscore the promising potential of Olive Mill Solid Waste (OMSW) as an affordable adsorbent for MB, hinting at its applicability for a diverse array of pollutant removal scenarios.