Efficacite photocatalytique des oxydes de fer (hematite) et des acides carboxyliques sur la degradation de derives phenoliques chlores en solution aqueuse

Abstract

The degradation of 2,4-DCP photoinduced by natural iron oxide was studied in aqueous suspension up on irradiation at 365 nm and by solar light. The effects of various factors, such as photolysis, adsorption, effect of pH, temperature, wavelength and the degradation pathways were investigated. The UV light has no considerable influence on the catalytic activity of the NIO, it is very important to note that there is a strong overlap between the absorption spectrum of NIO and the solar emission spectrum of the sun leading the capacity of this oxide to photoinduce the degradation of 2,4-DCP under solar light. 2,4-DCP was nearly completely removed in about 6 h. The second part of the work of this thesis has demonstrated the significant impact that could have sunlight on the activation of iron-carboxylate complexes in the degradation of 2,4-DCP. The complex iron-oxalate was found the most photocative for the degradation of 2,4-DCP in both systems (UV and solar irradiation). Photochemical behavior of iron released into solution, mostly influenced by pH, will monitor the effectiveness of the reaction disappearance of the pollutant. Our results showed that photocatalysis in the iron-oxalate system is an effective technique for the degradation of 2,4-DCP where seven major by-products were identified and that this degradation mainly through hydroxyle radicals •OH. Mineralization of 2,4-DCP was achieved in 11h in our experimental conditions. Furthermore, in the heterogeneous iron oxide /H2O2 system the method is effective only at acidic conditions and the disappearance of 2,4-DCP is strongly dependent on the concentration of H2O2 , substrate and catalyst dose. The photodegradation of 2,4-DCP can be directly attributed to the attack of •OH radicals. 2,4-DCP is totally degraded that after formation of various by-products can be completely mineralized to H2O, Cl- et CO2. Our work shows that the activation of natural iron oxide by carboxylic acids and hydrogen peroxide could have a considerable impact on the fate of organic pollutants in aquatic environment.