Fenton-and Photo-Fenton-Like Degradation of a Textile Dye by Heterogeneous Processes with Fe/ZSM-5 Zeolite

This work deals with the non-biodegradable azo-dye Orange II degradation by the heterogeneous Fenton-like and photo-Fenton-like processes using Fe/ZSM-5 zeolite as catalyst. The influence of some relevant parameters was studied, namely pH and temperature in the ranges 3.0-8.5 and 30-53 degrees C, respectively. The decolorization degree, the total organic carbon (TOC) removal, and the leaching level were evaluated along time in a slurry batch reactor. It was noticed that the degradation rate increased with temperature while leaching decreased when the initial pH value is more basic. It was possible to decolorize OII under less acidic conditions than those conventionally performed in Fenton's oxidation, compensating this with a slight increase of temperature, which is a promising approach since textile effluents are characterized by high temperatures and pH values. The results were significantly improved in the presence of UV/VIS radiation, with ca. 90% of TOC removal (for reaction times >= 10 h, depending on the other conditions). Besides, the photo-Fenton process exhibited also a lower dependence on reaction pH as compared to the Fenton's one and provided negligible Fe leaching from the zeolite support.