Filipa Duarte

Treatment of azo dye-containing wastewater by a Fenton-like process in a continuous packed-bed reactor filled with activated carbon

In this work, oxidation with a Fenton-like process of a dye solution was carried out in a packed-bed reactor. Activated carbon Norit RX 3 Extra was impregnated with ferrous sulfate and used as catalyst (7 wt.% of iron). The effect of the main operating conditions in the Chicago Sky Blue (CSB) degradation was analyzed. It was found that the increase in temperature leads to a higher removal of the dye and an increased mineralization. However, it also increases the iron leaching, but the values observed were below 0.4 ppm (thus, far below European Union limits). It was possible to reach, at steady-state, a dye conversion of 88%, with a total organic carbon (TOC) removal of ca. 47%, being the reactor operated at 50°C, pH 3, W(cat)/Q=4.1 g min mL(-1) (W(cat) is the mass of catalyst and Q the total feed flow rate) and a H(2)O(2) feed concentration of 2.25 mM (for a CSB feed concentration of 0.012 mM). The same performance was reached in three consecutive cycles.

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°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 Fentons 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 Fentons one and provided negligible Fe leaching from the zeolite support.