Resumo (PT):
Abstract (EN):
This work is the first known report dealing with the heterogeneous Fenton-like process in a continuous
stirred tank reactor. A Fe/ZSM-5 zeolite was used as catalyst for degradation of an azo dye (Orange II, OII)-
containing solution.
A parametric study was carried out to evaluate the effect of the main operating conditions in the basket
reactor performance, namely temperature (in the range 10–70 C), pH (1.5–4.0), feed hydrogen peroxide
concentration – [H2O2]feed (1.75–20.0 mM), contact time – W/Q (10–200 mg min/mL), residence time –
tresid (30–180 min) and the size of the catalyst particles (0.25 < dp1 < 0.60, 0.60 < dp2 < 0.80 mm and as
pellets, dp3 > 5 mm), for a OII feed concentration of 0.1 mM. Under the best operating conditions found
(pH = 3.0, T = 70 C, [H2O2]feed = 6 mM, W/Q = 200 mg min/mL, dp2 and tresid = 90 min), it was achieved
91% of discoloration and 36% of mineralization, at steady-state. Moreover, it was found a removal of
29% in terms of the chemical oxygen demand (COD), being worth noting the improvement in the effluent
biodegradability (k0 – oxygen uptake rate – increased from 9.3 to 23.2 mgO2/(gVSS h)) and the fact that the
final effluent is non-toxic (0.0% of Vibrio fischeri inhibition).
The stability of the catalyst performance was checked during five consecutive runs. The crucial factor
for the catalyst long-term use is the leaching of iron, which in all runs reached very low levels (e.g. only
0.173 mg/L of iron for the run in the optimized conditions, corresponding to only 0.13% of leaching). The
catalyst was characterized by different techniques before and after the reactions (namely SEM/EDS and
N2 adsorption); textural and chemical transformations during its use can be considered negligible (except
for very acidic conditions of pH = 1.5) favoring the catalytic stability of the Fe-zeolite.
Idioma:
Inglês
Tipo (Avaliação Docente):
Científica
Nº de páginas:
11