Fenton-Type Bimetallic Catalysts for Degradation of Dyes in Aqueous Solutions

Bebiana L C Santos,António M Fonseca,Manuel F R Pereira,Pier Parpot,Isabel Correia Neves,Olívia S G P Soares,Elisabetta Rombi

doi:10.3390/catal11010032

Abstract

Dye compounds are becoming a problematic class of pollutants for the environment, so it is important to develop stable catalysts for their elimination. First, several studies were performed with different Y zeolites (NaY, (NH4)Y and USY) in order to select the best support for the preparation of the bimetallic catalysts. In particular, NaY zeolite was used as the support for Fe, Cu and Mn metals to prepare mono and bimetallic Fenton-type catalysts by the ion exchange method. The catalysts were characterized by several techniques, such as chemical analysis, nitrogen physisorption, X-ray diffraction (XRD), scanning electron microscopy (SEM) and cyclic voltammetry studies. Characterization results revealed that the metals were successfully ion-exchanged within the NaY zeolite. The prepared catalysts were tested for the aqueous-phase degradation of dye compounds (Procion yellow (PY) and Tartrazine (Tar)) at atmospheric pressure and different temperatures, using H2O2 as the oxidant. All the investigated samples were found to be active in degrading the dyes through the Fenton-type process; however, the oxidation rate was found to be higher in the presence of the bimetallic catalysts. CuFe-NaY displays the best mineralization rate for PY oxidation while MnFe-NaY shows the highest activity for Tar degradation. This work may provide further insight into the design of Fenton-type bimetallic catalysts with improved catalytic properties for environmental remediation.

Highlights

The discharge of dyes into water resources, in addition to unaesthetic effects, has far more dangerous repercussions on health, since some of them are carcinogenic and mutagenic; this is why their removal from the environment is a very important issue
Several heterogeneous Fenton-like catalysts containing iron supported on zeolites [8,9] or iron and copper supported on mesostructured silica [10] have been reported to be efficient catalytic systems for oxidative degradation reactions
Several heterogeneous Fenton-like catalysts containing iron s2uopf-17 ported on zeolites [8,9] or iron and copper supported on mesostructured silica [10] have been reported to be efficient catalytic systems for oxidative degradation reactions

Summary

Introduction

The discharge of dyes into water resources, in addition to unaesthetic effects, has far more dangerous repercussions on health, since some of them are carcinogenic and mutagenic; this is why their removal from the environment is a very important issue. 40C/C0 valu7e0s, (C/C0)fin3al, of 28 and 15%6a8re found at these8.t9emperatures f2o4r.t2he CuFe-NaY 45and FeCu4-N5 aY catalyst2s8, respectively. An oxidation process at around 1.0 V vs SCE can be noticed for FeCu-NaY and CuFe-NaY modified electrodes Considering that this last potential region corresponds to the Fe(II)/Fe(III) couple, the contribution of Fe(II) species can be foreseen in this case. The lower values obtained for the pseudo first-order rate constant for CuFe-NaY and MnFe-NaY are consistent with the catalytic results observed for the degradation of PY (Figure 7) and Tar (Figure 9). Interesting, for both dye compounds, the best catalyst was that where the iron was introduced as second metal. In both these catalysts the amount of iron is almost the same, with 3.49 wt% for CuFe-NaY and 3.84 wt% for MnFe-NaY (Table 1); the decrease in the BET surface appears related to the amount of iron, the large amount of iron in MnFe-NaY imply a high decrease in the BET surface area (Table 2)

Reutilization of the Bimetallic Catalysts

Catalysts Preparation

Catalysts Characterization

Catalysts Evaluation

Findings

Conclusions