Azo-dye orange II degradation by the heterogeneous Fenton-like process using a zeolite Y-Fe catalyst—Kinetics with a model based on the Fermi's equation

Abstract

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

Heterogeneous Fenton’s oxidation using Fe/ZSM-5 as catalyst in a continuous stirred tank reactor

“…Results obtained allowed concluding that the zeolite catalyst is stable, as reported in similar studies [5], or even more stable. In fact, Idel-aouada et al [26] observed a little decrease of acid red 14 dye reduction (from 100 to 93% in the 1 st vs. 3 rd run, respectively) when using a Fe(II)-Y zeolite as catalyst, while other authors noticed some decay of activity with other supports like saponite clay [9]; activated carbons also proved to be stable [8,14].…”

“…Moreover, under such conditions the formation of ferrous/ferric hydroxide complexes occurs, which lead to the deactivation of the ferrous catalyst [50]; moreover, the oxidation potential of the hydroxyl radical also decreases with increasing pH (2.65-2.80 at pH = 3 and 1.90 V at pH = 7) [11]. On the other hand, the decreased efficiency of the process at very acidic pH values may be related to the decreased generation of hydroxyl radicals, once the hydrogen peroxide forms the hydroperoxonium ion (H3O2 + ) by proton solvation, and therefore does not react with iron [5]. However, in terms of iron concentration in the effluent, lower pH values provide rather poor results (Figure 8 b), so that for pH = 1.5 the limit of 2 ppm of iron is exceeded, showing a great leaching of the initial iron present in the catalyst.…”

“…These compounds, and due to their complex structure, can hardly be removed by biological or physical-chemical processes such as coagulation / flocculation, sedimentation, flotation, filtration and adsorption. Moreover, in most of such processes there is only transfer of the dyes from one phase to another, rather than their destruction [5].…”

“…This removal requires the inclusion of another stage in the treatment process, thus making it more expensive and complex [7]. To minimize these disadvantages, different forms to attach the iron species to a porous solid matrix (such as a zeolite, clay or activated carbon support) were studied -socalled heterogeneous Fenton-like process [5,8,[9][10][11][12][13][14][15].…”

Modular Polyoxometalate‐Layered Double Hydroxide Composites as Efficient Oxidative Catalysts

“…[30] The increase of temperature promotes the generation of radicals and the subsequent attack to the dye molecules. [31] It can be found that complete dye degradation can be obtained at 30, 45 and 60 o C after 140 min. Despite the fact that the MB degradation at 30 o C is not as fast as those observed at higher temperatures, the performances of MB removal at 30 o C is chosen to carry out the following studies based on the fact that use of lower temperature reduces considerably associated larger scale operational cost and eliminate the possibility of catalyst leaching after prolonged operation times.…”