Etude de la photodégradation de polluants organiques induite par les polymères de coordinations « CPs » en solution aqueuse.

Abstract

This thesis examines a promising new method for the effective depollution of water contaminated by organic pollutants such as pharmaceutical products. This advanced oxidation method is based on heterogeneous photocatalysis. In this context coordination polymers are currently considered as promising candidates for various applications. However, the literature on the photocatalytic activity of these solids has exploded only very recently, although the use of these materials as heterogeneous photocatalysts might be advantageous when compared with classical semiconductors. In the first part, the degradation of ibuprofen used as a model pollutant was carried out in a homogeneous medium. In this direction various methods have been established; direct photolysis, photo-oxidation with hydrogen peroxide and persulfate. The results showed that the degradation process is relatively fast at 254 nm and negligible at 365 nm and that the assisted photolysis S2O82-/UV showed better efficiency than direct photolysis and then the H2O2/UV system for the degradation of the IBP. In the second part, the heterogeneous systems using two synthesis coordination polymers (CPs) were studied. A preliminary study was devoted to the identification and characterization of CPs by a combination of experimental technics (Xray diffraction, TGA analysis, FTIR spectroscopy, UV-Visible , cyclic voltametrie…). The efficiency of these CPs was evaluated by monitoring the degradation of IBP in different systems CPs/UV, CPs/H2O2/UV, CPs/S2O82-/UV. The influence of several factors, such as pH, concentration of the CPs and the substrate in all previous systems , on the photodegradation of IBP has been demonstrated. Comparison between previous systems in kinetic and mechanistic terms shows an improvement in the reaction rate by the supply of S2O82-. The mechanistic aspect was also taken into account and shows the role of the oxidative radicals involved in the photochemical process which would involve the radical •OH for the IBP/CPs et IBP/CPs/H2O2 systems then the conjugated effect of the radicals SO4•- and •OH particularise the case of IBP/CPs/S2O82-. The mineralization has been monitored and the degradation mechanisms of the different systems have been proposed. Experiments in the natural simulated environment have been carried out and show the feasibility of the photochemical process in the environment. In addition, the presence of certain elements present in aquatic environment such as inorganic ions and metals have been examined and reveal the influence of these elements on the photochemical process.