Contribution des complexes organiques de Fe(III) dans la photodegradation de polluants organiques en solution aqueuse en lumière naturelle et simulée

Abstract

The mutual effect of light and organic complexes of Fe(III) on the photodegradation of 3-methylphenol (3MP) was investigated in homogeneous phase. A preliminary study of the organic complex Fe(III)-3MP mixture in the absence of light and at room temperature confirmed the absence of interaction in the ground state. The second part, devoted to the study of the degradation of 3MP induced by complex under irradiation at 365nm revealed the disappearance of the substrate. The effect of various factors on the 3MP photodegradation such as pH, oxygen and the excitation wavelength was examined. The addition of hydrogen peroxide in the organic complex Fe(III)-3MP mixture improves significantly the rate of 3MP disappearance condition at acidic medium. The use of tertio-butanol as a scavenger confirmed the intervention of hydroxyl radicals in the 3MP photodegradation at all the Fe(III)complex used. 3MP degradation mechanisms have been elucidated and photoproducts are similar for both the studied complex. To highlight the nature of the interaction between Fe(III)-complexes and phenolic compounds, three derivatives of phenol pollutants were chosen (3,5-DMP, 3MP, 3 -methyl, 5- hydroxy phenol). The disappearance rate appears to be related to the nature of the substitution.The mineralization process shows that the life of intermediates is much higher than 3MP. To get closer to the environmental conditions, the effect of main elements present naturally in the aquatic ecosystem such as humic substances and bicarbonates was examined and we looked at their transformation under solar irradiation. The results show that such systems operate with lower kinetic than those observed in artificial irradiation. These results provide some knowledge on the fate of phenolic pollutants in the aquatic environment and on the photocatalytic treatment by the organic complex iron (III). These results are very encouraging for the application in the environment