Comportement d’un oxyhydroxyde de Fe(III) vis-à-vis d’un produit pharmaceutique en solution aqueuse en présence de lumières naturelle et simulée

Abstract

Our objectives in this thesis were to demonstrate the effectiveness of Goethite (GOE) in the amoxicillin (AMX) photodegradation process under artificial and solar irradiation by different systems, as well as the optimization of experimental parameters affecting the rate of the degradation. Different analytical methods have been used in the characterization of AMX and GOE. In the absence of light, the transformation of AMX was studied in different mixtures (AMX-GOE, AMX-GOE-H2O2 and AMX-GOE-Carboxylic Acid). An interaction between AMX and GOE was demonstrated; H2O2 significantly improved the degradation of AMX while no effect was mentioned in the case of the presence of carboxylic acids. Under irradiation and in the absence of GOE, AMX was found to be photolysed at 254 nm and refractory to photolysis at 365 nm (monochromatic and polychromatic); this is due to the overlap between the absorption spectrum of AMX and the light source. The photodegradation of AMX by heterogeneous photocatalysis in the presence of GOE has been studied. Results show that the photodegradation is dependent on several parameters such as pH, substrate and catalyst concentration. The use of free radical inhibitors has shown that the reaction mechanism is dominated by •OH radicals where oxygen plays an important role. The addition of H2O2 to the solution improves the degradation of AMX and increases its rate of mineralization in terms of chemical oxygen demand. The degradation is effected by the contribution of the •OH radicals and also by oxidation on the surface of GOE. The AMXGOE-carboxylic acid system has been tested, among the used acids, oxalic acid was the only one that showed a photo-activity. By comparing the degradation kinetics of AMX in natural and artificial light in the three studied systems, it is found that the degradation rate is higher under solar irradiation.