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A natural iron oxide (NIO) was applied for the photodegradation of 2,6-dimethylphenol in presence of polycarboxylic acids under UV irradiation. The dependence of 2,6-DMP degradation was attributable to the formation of dissolved Fe–polycarboxylate in the solution and adsorbed on the surface of natural iron oxide. The results showed that the photodegradation of 2,6-DMP could be enhanced greatly in the presence of oxalate. The variables studied were the aqueous pH, the presence of hydrogen peroxide and temperature in NIO / oxalate / UV system. The optimal pH value was found to be in the range of 3–4. It was found that the formation of Fe (II) in NIO / oxalate system occurred more vigorously at the initial stage and gradually became moderate. Furthermore, the formation of H2O2 during the photoreaction was studied to explore its relationship with the photodegradation efficiency and the iron cycling process. The use of 2.0% of isopropanol as a scavenger confirmed the intervention of hydroxyl radicals in the degradation of 2,6-DMP.

The degradation of isoproturon 3-(4-isopropylphenyl)-1,1dimethylurea photoinduced by Fe(III) in aqueous solution has been investigated. The rate of degradation depends on the concentration of Fe(OH)2+, the most photoreactive species in terms of .OH radical formation. These .OH radicals are able to degrade isoproturon until total mineralisation. The formation of Fe(II) in the irradiated solution was monitored. The sonophotochemical degradation of isoproturon has been found to be dependent on the intensity of sonication. The combination of ultrasound and photochemistry has been used to degrade an aqueous solution of Isoproturon (IP). The degradation of IP in aqueous solution was investigated under sonolysis at 500 kHz and in the presence of Fe(III), as well as under simultaneous sonolysis and photoinduced Fe(III). Coupling photolysis with ultrasound for degradation of IP has been developed. The photosonochemical decomposition rate constant is greater than the additive rate constants of the two processes. Degradation products were analysed by CG/MS performed in the electron-impact (EI) mode, at 70 eV potential using full scan mode. Degradation photoproducts were identified and a mechanism of degradation is proposed for two processes.

A heterogeneous photo-Fenton-like degradation process of 1-naphthol (1-NP) promoted by natural iron oxide (NIO) in the presence of H2O2 was studied under artificial (365 nm) and solar irradiation. This is an important reaction for the environment since both H2O2 and iron oxides are common constituents of natural waters. Furthermore, iron oxides function as catalysts in chemical oxidation processes used with H2O2 for treatment of contaminated waters. The NIO used in this study was characterized by X-ray diffraction (XRD), X-ray fluorescence and Brunauer–Emmett–Teller (BET) methods. The results show that the NIO is a composite material that contains predominantly crystalline hematite particales (Fe2O3). The Fe2O3 in NIO was able to initiate the Fenton-like and photo-Fenton-like reactions. The effects of initial pH, catalyst dosage, H2O2 concentration and the wavelength of the light source (UV and solar) on the photodegradation of 1-NP were investigated. The optimal content of the NIO was 1 g L-1 and the optimal H2O2 concentration was 10 mM. The degradation could occur efficiently over a wide pH range of 3-8.3. Furthermore, an important effect of light was observed. The photo-oxidation of 1-NP in NIO-H2O2 system under solar light was significantly accelerated in comparison with artificial irradiation at 365 nm.

In this work, the methylene blue (MB) heterogeneous photodegradation was investigated in the natural iron oxide (NIO) and oxalic acid process under UV irradiation. The adsorption of MB onto the surface of NIO was found favorable by the Langmuir approach. Under the operating conditions of this study, the photo-Fenton reaction was set up in co-presence of NIO and Oxalic Acid (OA). Where, the total degradation of MB was achieved in 90 min. The mechanism of MB photodegradation was discussed and the use of 2.0 % of tertiobutanol as a scavenger of •OH confirmed their intervention in the reaction. The effect of oxygen and hydrogen peroxide were investigated, the results demonstrated that the oxygen was necessary in the MB photodegradation and that the optimum concentration of hydrogen peroxide was found to be 5x10-4 M. measuring the chemical oxygen demand (COD) demonstrates the effectiveness of our natural iron oxide in the degradation of organic pollutants.

The voluntary or accidental release of chemical compounds in the environment is a major cause of pollution of natural waters. Most of chlorophenols are toxic and hardly biodegradable and are difficult to remove from the environment. Therefore, it is important to find innovative and economical methods for the safe and complete destruction. The objective of this work is to test the activity photocatalytic of natural iron oxide (NIO) in the photodegradation of 2-chlorophenol (2-CP). The analysis chromatographic with HPLC of solutions exposed under UV irradiation revealed that the degradation of 2-CP was negligible under the condition of using only natural iron oxide. The effect of wavelength on photoreactivity of NIO was also investigated in this process: at high wavelength thus at low energy the efficiency of degradation is important. We have also investigated the activation of NIO by hydrogen peroxide and oxalic acid, The results showed that the photodegradation of 2-CP under UVA irradiation could be enhanced greatly in the presence of oxalate. 2-CP was completly removed after 240 minutes of irradiation when the concentration of oxalic acid is equal to 2.10-3 M. The use of 2.0 % of isopropanol as a scavenger confirmed the intervention of hydroxyl radicals in the photodegradation of 2-CP.

This study focused on the decolorization of bromocresol purple (BCP) using Fe (III) oxyhydroxide (Goethite) as an inducer. The mixture dye- Goethite in dark condition and ambient temperature, shows a reaction between the dye and the Fe (III) oxyhydroxide. Indeed, the tracking of the reaction using UV-visible spectrophotometry showed a low decrease in the principal band of the dye. This reveal the existence of an interaction between the substrate and the Goethite whitch is important in acidic medium. The irradiation at 365 nm of mixture Goethite-BCP (1g.L-1- 10-4 M) leads to a transformation of substrate. The decrease of the band at 432nm and the presence of an isosbestic point at 508 nm support the transformation of BCP. The substrate kinetics disappearances are improved in acidic medium. The addition of hydrogen peroxide (5.10-3 mol.L-1) in a suspension of Goethite, accelerate significantly the rate of disappearance of the dye. Natural radiation tests showed that the degradation was faster than artificial one at 365 nm. Studies on mineralization using COD method certify that this method, compatible with the environment, may be considered in the treatment of wastewater.

The present work involves the prospects of the kinetics study for photocatalyticdecolorization of an azo dye (Alizarin yellow) in aqueous solution with TiO2 Degussa P25 as photocatalyst in slurry form using UV-A light at 365nm.The results showed that the adsorption of alizarin yellow on TiO2 P25 was found negligible and discoloration of this dye by TiO2/UV system is much faster than with direct UV photolysis. Additionally, the effects of various parameters such as initial dye concentration, catalyst dosage,H2O2 concentration, addition of alcohols and presence of inorganic salts on decolorization have been investigated. The removal rate of Alizarin yellow indicated an inverse dependence on the initial dye concentration. The optimal content of the catalyst was 1 g.L-1. The disappearance kinetics was strongly enhanced in the presence of electron acceptors such as H2O2.However,the presence in the reacting system of Cl-, SO42- (Addition of dye assisting chemicals such as Cl- and SO42-)inhibits the dye removal rate. The study of the effect of different type of TiO2 on the decolorization reveals the following order of efficiency: TiO2- P25> TiO2Tiona PC.

The study of 3-methylphenol (m-cresol) photodegradation has been achieved in two system, UV / Fe(III)-Cit and UV / Fe(III)-Cit / H2O2 in natural (pH = 6.5). The presence of H2O2 in UV / Fe(III)-Cit system reduce the efficiency of m-cresol degradation at low concentration, however for the high level of H2O2 the process is improved. The optimal concentration of H2O2 was found to be 5 mM. This can be probably explained by a low Fe(II) formation of in this system. The result shows in the both systems that the acidic media is favorable for this kind of reaction. The Comparison between the aquacomplexes and Fe(III)-Cit complex in the presence or absence of H2O2 have confirmed that the best condition of m-cresol degradation was achieved with the addition of H2O2. Additionally, the use of 1.0 % of tertiobutanol as a scavenger confirmed the intervention of hydroxyl radicals in the m-cresol photodegradation.

Le présent travail porte sur la photodégradation d’un colorant azoté ‘’ l’Orange G‘’ à température ambiante en présence d’une suspension aqueuse de dioxyde de titane. L’influence de différents paramètres (semi conducteurs de la série PC ‘’Tiona’’, pH, anions inorganiques, H2O2 et S2O82-) sur l’orientation et la vitesse de la réaction a été examinée. Au cours de cette étude, nous avons montré que la cinétique de disparition photocatalytique de l’Orange G suit bien le modèle de Langmuir-Hinshelwood. Par ailleurs les capacités photocatalytiques des TiO2 de la famille des Tiona PC sont moins efficaces que celles du Degussa P25, même s’ils présentent des surfaces spécifiques plus élevées. L’alcalinisation du milieu réactionnel accélère considérablement la disparition de l’OG. Nous avons également constaté que la présence des ions (Cl-, CO32-, NO3-) inhibe légèrement la photocatalyse de l’Orange G tandis que l’addition de H2O2 et de S2O82- améliore les performances de dépollution par la technique photocatalytique. Cependant, l’utilisation de H2O2 en excès conduit à un effet de piége pour les radicaux HO•.

la dégradation du 2,6-diméthylphénol (concentration initiale de 5x10-4 M) un des dérivés phénolique utilisé comme intermédiaire dans la fabrication de plusieurs produits industriels comme les résines, les antioxydants, les désinfectants et les vernis a été étudiée par les deux procédés Fenton (H2O2/Fe2+) et photo-Fenton (H2O2/ Fe2+ /UV). Les réactions ont étéréalisé avec les rapports [H2O2]0 / [Fe2+]0 = 0,5, 1 et 2, la concentration du 2,6-DMP étant identique à celle de Fe2+ (5x10-4 M). Le taux d’abattement du 2,6-DMP est de 46 %, 68 % et 80 % pour les rapports 0,5, 1 et 2 respectivement avec le réactif de Fenton. Cependant nous avons remarqué une accélération de la disparition du 2,6-DMP par irradiation du réactif de Fenton à 365 nm qui est attribuée à la production supplémentaire de radicaux HO•. Cette production résulte de la photoréduction des ions ferriques formés dans l’étape antérieure de décomposition de H2O2 par les ions ferreux (réaction de Fenton). L'irradiation du réactif de Fenton à 254 nm et à 365 nm a montré une dégradation totale du 2,6-DMP à 365 nm, alors qu'a 254 nm le taux d’abattement est de 50 % au bout de 20 minutes d’irradiation et atteint un pallier à cause de la consommation totale de H2O2. La cinétiquede disparition du 2,6-diméthylphénol a été suivie par HPLC ou un nombre d'intermédiaires a été détectés et un mécanisme réactionnel est proposé.

La dégradation photocatalytique a été étudiée en utilisant le TiO2 Degussa P25. L'effet de la concentration du photocatalyseur sur la cinétique de disparition de IP a été étudié en utilisant différentes concentrations de TiO2 allant de 0 à 2 g.L-1.La disparition totale de IPa été atteinte au bout de 350 minutes pour une concentration de 1,0 g.L-1 de TiO2. Les cinétiques de dégradations ont été modélisées par l’équation de Langmuir-Hinshelwood, par laquelle les constantes k apparentes de vitesse et la constante K d'équilibre d’adsorption ont été évaluées. La dégradation a été étudiée en fonction de plusieurs paramètres tel que lepH, la concentration en substrat, en présence d'accepteur d'électron tel que le peroxyde d'hydrogène (H2O2) et le persulfate de potassium (K2S2O8) et en présence de l'alcool en tant que piège a radicaux hydroxyle. L’effet de l’addition de quelques ions (Cl-, NO3- et SO42-)sur la dégradation de IP a été également étudié. Les produits intermédiaires ont été identifiés par chromatographie liquide couplée à la spectrométrie de masse (LC-MS). Les produits principaux par ordre d'importance étaient les produits ortho- et méta hydroxylé et composés d'oxydation sur la chaînes urée qui mène au produit de la déméthylation

Les applications principales du charbon activé sont entre autres la purification, décoloration, désodorisation et en générale la désintoxication des eaux potables ainsi que la purification de l’air et des produits chimiques, alimentaires…etc.L’investigation a porté sur l’adsorption du vert de méthyle sur ce type de charbon activé. Les études menées en « batch méthodes » ont permis de déterminer le temps de contact (90 minutes par 80% de rendement d’élimination et pour une concentration de 30 ppm en substrat). Cependant ce temps de contact peut varier avec la concentration en colorant. L’influence de paramètres comme : la température, l'agitation et la concentration initiale ensubstrat, ont permis de constater une amélioration sensible de la capacité et de la vitesse d’adsorption du vert de méthyle sur ce support. Par ailleurs, l’adsorption de ce composé est bien décrit par les modèles cinétiques de Langmuir et Freundlich.