Photodegradation des produits pharmaceutiques induite par les complexes organiques de Fer(III) en solution aqueuse.

Abstract

This work is a contribution to the photodegradation of three pharmaceutical compounds: diclofenac (DCF), aspirin (ASP) and carbamazepine (CBZ) induced by organic complex of Fe(III) (Fe(III)Cit) in homogeneous phase under simulated and sunlight. A first part was devoted to the synthesis and characterization of Fe(III)Cit complex, which confirms its stability, its stoichiometry, while the effect of light irradiation revealed its photolysis, which generated the HO• radical. This oxidizing species has shown its effectiveness in the elimination of PP. In the second part of the work, the study of PP-Fe(III)Cit mixtures in aqueous solution was undertaken in the absence and presence of light. Indeed, in the dark, the three substrates showed no interaction with Fe(III)Cit complex in aqueous solution when the mixture ages at room temperature. Under irradiation, the photodegradation of substrates induced by Fe(III)Cit complex, followed by spectrophotometry and HPLC, shows rapid kinetics in the beginning of reaction and then slowed down during the irradiation. This reaction appears to be dependent on several parameters such as pH, substrate and complex concentration. The Fe(II) and the hydrogen peroxide resulting from the photolysis of the complex have been quantified and highlight the involvement of the Fenton reaction in the oxidation process of PP. The mechanistic study reveals that hydroxyl radicals are involved in the photocatalytic process and this whatever the substrate used. The identification of the reaction intermediates by LC-MS made it possible to establish a degradation mechanism for each substrate. The following of the mineralization shows that the life of intermediates reaction is much greater than the starting product. To activate the photocatalytic process, the addition of hydrogen peroxide in the mixture DCFFe(III)Cit improves significantly the rate of disappearance of the substrate. To get closer to the environmental conditions, the effect of main elements present naturally in the aquatic ecosystem such as humic substances, bicarbonates and metals was examined and shows the need to take into account the impact of these elements. In order to verify the feasibility of the photochemical process in the environment, the same systems were studied under solar irradiation. The results show that such systems operate with higher kinetics as those observed in artificial irradiations..