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The photolysis of iron(III) organic complexes in the presence of natural and simulated light was a concern for the role it plays within the environment in terms of producing hydroxyl radicals able to degrade organic products. In the present work, the study focused on two iron(III) organic complexes. The characterization of these complexes by spectrometry allowed to show their stability in environment with a stability constant equal to Log β = 13.13 for the complex Fe(III)-malonate, and Log β = 20.85 for the Fe(III)-malate complex. Photolysis of these complexes was carried out using a lamp at 365 nm at different pHs, and followed by several assay Fe(II), H2O2 and •OH. The complexes present different photo-reactivities, in the case of Fe(III)-malate, the photolysis is favored by the Fenton process and generates hydroxyl radicals, contrarily to Fe(III)-malonate photolysis which generates an oxidizing •CH2COOH radical without formation of H2O2 nor of •OH. The presence of oxygen and the addition of isopropanol and chloroform show different effects on the complex photolysis. Complexes mineralization at natural irradiation was also studied using chemical oxygen demand (COD).

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The Fenton process has been widely studied in the treatment of wastewater but unfortunately this process can only work under acidic pH conditions. To overcome these disadvantages, the Fenton modified by adding chelating agents such as oxalic acid (Ferrioxalate complex (Fe(III)Ox) since its high solubility in aqueous media can broaden the available pH range of the Fenton reaction to near neutral pH. In this study, The photooxidation efficiencies of 3-methylphenol (3MP) catalyzed by Fe(III) and oxalic acid was investigated. The results show that the photodegradation Of 3MP is slow in the presence of Fe(III) or oxalic acid alone. However, it is markedly enhanced when Fe(III)Ox complex coexist. The concentration of the complex is optimized to the ratio ([Fe(III)Ox] = 3/12). Fe(III)Ox plays a positive role in the photo-Fenton system, especially at higher pH = 5.5. Oxygen is essential to the formation of oxidative species and, as a consequence, for the pollutant degradation. Additionally, the use of tertio-butanol as a scavenger confirmed the intervention of .OH in the 3MP photodegradation. 3MP degradation mechanisms have been elucidated and photoproducts are identified by comparison with authentic products. 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. The photodegradation of 3MP through Fe(III)Ox system under solar light was significantly accelerated in comparison with artificial irradiation at 365 nm. Measuring chemical oxygen demand (COD) leads to mineralization which decreases the toxicity of 3MP solution. This work also demonstrates that this system is an encouraging method for the treatment of organic pollutants in the natural environment.