Valorisation des matériaux locaux pour l’élimination des produits pharmaceutiques par procédés physico-chimiques de traitement

CHEBBI, Meriem (2024) Valorisation des matériaux locaux pour l’élimination des produits pharmaceutiques par procédés physico-chimiques de traitement. Doctoral thesis, Faculté des sciences et technologie.

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Abstract

The present study aimed to investigate the laboratory-scale removal of an antibiotic and a steroidal anti-inflammatory, "metronidazole" and "prednisolone", from synthetic solutions and to pre-treat wastewater from a medical analysis laboratory, using an adsorbent derived from pine cones. To achieve this objective, four adsorbents were prepared from pine cones and another commercial powdered activated carbon. The first three prepared biochars underwent a single pyrolysis step at 500, 700 and 900°C named PCB-500°C, PCB-700°C and PCB-900°C, respectively, while the fourth prepared adsorbent was activated with phosphoric acid and then subjected to pyrolysis at 400°C (PhAC). Infrared characterization of the adsorbents used in this study showed that the chemical surface contains several functional groups (C=O, C=C and C-O-C). DRX analysis indicated that their structures are amorphous and although aromatic for PCB-900°C and CAP. BET results showed that specific surface area increased with pyrolysis temperature, and that phosphoric acid impregnation can affect specific surface area despite the low pyrolysis temperature. The results of adsorption tests clearly demonstrated that PCB-900°C outperformed the other prepared adsorbents, achieving 98.56% and 99.10% efficiency in the removal of metronidazole and prednisolone within an equilibrium time of 30 minutes, respectively. Adsorption of the two pharmaceuticals is chemical rather than physical in nature for PCB-900°, PhAC and CAP as the pseudo-second-order kinetics model perfectly describes the experimental data. The maximum Langmuir adsorption capacities obtained with the prepared adsorbent (PCB-900°C) were 138.94 mg/g and 35.99 mg/g for metronidazole and prednisolone, respectively. The adsorption process was not affected by pH medium variations; thus, the electrostatic interaction did not have a major effect on adsorption process. The π-π interaction mechanism, pore-filling and hydrophobic interactions were considered the predominant adsorption mechanisms for both pharmaceuticals adsorption on PCB-900°C. Adsorption of prednisolone in the presence of metronidazole is antagonistic, due to the competitive nature of the pharmaceuticals on the PCB-900°C surface. According to the thermodynamic study, metronidazole and prednisolone adsorption were spontaneous and of endothermic character. The reuse of PCB-900°C was tested over 8 cycles for metronidazole and 4 cycles for prednisolone. The results of organic matter degradation in laboratory wastewaters showed efficiency in reducing chemical oxygen demand (COD) and turbidity levels. Therefore, pine cone-derived biochar may be considered a promising adsorbent for the removal of metronidazole and prednisolone from aqueous solutions.

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