| Due to the inability of biological treatment processes to treat highly contaminated and toxic wastewater with organic pollutants, advanced oxidationprocesses (AOPs) are of great interest for the destruction of toxic and biorefractory organic pollutants found in industrial wastewater and in landfill leachate. Homogeneous Fenton processes are one technology of AOPs, they are considered as a series of most promising technologies for the remediation of wastewaters containing a variety of toxic substances. There are two major drawbacks that limit the industrial application of this technology:(1) the tight range of pH (e.g., pH 2-4) in which the reaction proceeds and (2) the need for recovering the precipitated catalyst after the treatment. The resulted sludge may contain organic substances, as well as heavy metals and has to be further treated, increasing thus the overall costs. However, in order to overcome the major drawbacks of the homogeneous system, heterogeneous Fenton-type systems have been prepared to catalyze the oxidation of various organic compounds in mild reaction conditions.(1) Two series iron-based mesoporous silica materials were prepared according to different impregnation procedures. Several complementary techniques, including XRD and nitrogen sorption isotherms were used to evaluate the final structural and textural properties of the calcined Fe/SBA-15 materials. Catalytic performances of all the materials were evaluated in the heterogeneous Fenton system. The samples SBA15-acFe (NO3)-2 and SBA15-acFe (NO3)-1, prepared by self-combustion of an iron-glycinic complex within the silica porosity, have showed their good catalytic activity and stability. The sample SBA15-iFeEDTA-1 and SBA15-iFeEDTA-2, using C10H12FeN2NaO8 as iron precursor, have good catalytic activity, but their stability was decreased when the content of iron increased. The sample SBA15-iFe (NO3)-1 and SBA15-iFe (NO3)-2, prepared by classical wet impregnation of the silica support by iron nitrate, have excellent stability, but catalytic activity of these two samples were not good.(2) Iron-based mesoporous silica materials were prepared according to different impregnation and co-condensation procedures. Several complementary techniques, including XRD, TEM/EDX and nitrogen sorption isotherms were used to evaluate the final structural and textural properties of the calcined Fe/SBA-15 materials. While Fe2O3 isolated particles of which the size is close to the silica pore diameter (～7-8 nm)were obtained using classical wet impregnation procedure, smaller iron oxide particles(-2-4 nm) homogeneously dispersed within the hexagonal pore structure of the SBA15 host support were generated through more sophisticated impregnation route (namely selfcombustionof an impregnated iron glycinic complex). By contrast, the various cocondensation routes used in this work were less efficient to obtain iron oxide nanoparticles inside the silica mesopores. Catalytic performances of all the materials were evaluated in the case of total phenol oxidation by H2O2 in aqueous solution at ambient conditions. Large differences in terms of catalytic activity and iron species stability were observed. While the impregnated solids proved to be the most active catalysts (highest iron oxide nanoparticles dispersion), iron leaching was observed in aqueous solution, accounting for a homogeneous catalytic contribution. In contrast, the co-condensed samples exhibiting larger iron oxide clusters stabilized over the silica surface proved more efficient as active sites in Fenton catalysis.(3) Novelγ-Al2O3, with a large pore size and a high surface area, was prepared as support. Alumina-supported iron oxide and iron-based perovskite are synthesized. Several complementary techniques, including XRD, TEM/EDX and nitrogen sorption isotherms were used to evaluate the final structural and textural properties of the two samples.Evaluation of the nanocomposite reactivity for the oxidation of phenol indicated an improved catalytic activity for the two novel samples (iron and lanthanum-iron on alumina) than those exhibited by the corresponding bulk perovksite or optimized reference catalysts. Among all the tested samples, the novel LaFe-Almeso composite (an alumina-supported lanthanum iron mixed-oxide) presents the highest activity with excellent stability in reaction.(4) Al-pillared Fe-Smectite was prepared and used as heterogeneous catalysts for the photo-Fenton decolorization of azo dye C.I. Acid Orange 7 under UV irradiation. UV irradiation is found to enhance the activity of the catalyst in the heterogeneous photo-Fenton process. Catalyst loadings of 0.5 g/L and 13.5 mM of hydrogen peroxide yield a remarkable decolorization, accompanied by excellent catalyst stability. An experimental design based on the response surface methodology is applied to assess the individual and interaction effects of several operating parameters namely hydrogen peroxide concentration, pH and catalyst loadings on the treatment efficiency. It is that the pH and H2O2 are found to be the vital parameters affecting dye degradation. The result of the response surface methodology design and the full factorial design (FFD) were compared. |
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