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Fe-clay catalysts have been prepared and tested for Orange II oxidation with H2O2 in aqueous solution. The reaction is carried out in a batch reactor, using different hydrogen peroxide concentrations, and in a wide range of temperature and pH values. Twelve samples were prepared, with three different iron loads (7.5, 13.0 and 17.0 %, w/w), and using four iron salts as precursors, namely Fe(II) acetate, Fe(II) oxalate, Fe(II) acetylacetonate and Fe(III) acetylacetonate. The samples were characterized using X-ray diffraction, thermal analysis, infrared spectroscopy and adsorption of nitrogen at 77K. The catalytic results show that these solids present good catalytic properties for the degradation and mineralization of Orange II solutions, allowing to reach, in the best conditions and after 4h of oxidation, 99% of dye degradation with 91% of TOC (Total Organic Carbon) reduction (at 70ºC), using only ca. 90 mg of clay catalyst per litre of solution. Nevertheless, 96% of dye removal with 82% of mineralization were also reached at 30ºC. Besides, the amount of iron released into the final solution is lower than 1 ppm, in the worst of the cases, and 0.09 ppm in the best case.

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The degradation of Orange II dye (OII) by a heterogeneous Fenton-like process was studied using a catalyst with 5 wt.% of iron after ion-exchange in a Na-Y zeolite support. The catalyst was characterized by X-ray diffraction (XRD), N2 adsorption, atomic absorption spectroscopy and X-ray fluorescence (XRF). The effect of the initial concentrations of H2O2 and OII, pH and temperature on the degradation rate of OII was investigated by carrying out experiments in a batch reactor. The OII concentration histories (i.e., concentration evolution along reaction time) were described by a simple semi-empirical kinetic model, based on the Fermi's equation, which captures simultaneously the influence of all the reaction conditions with a few adjustable parameters. The adherence of the model to the data was remarkable, and the effect of the operating conditions on the obtained fitting parameters -apparent rate constant and transition timewas analyzed.2

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